Empathy List Archives

LM

Laurence Motteram

Fri, Mar 5, 2010 1:03 AM

Don't be misled by the working display, as it has its own
microprocessor. The digital PCB has two LM2940CT devices, but it sounds
like the one in question supplies the digital +5V. Naturally,
everything connects to this, but you might like to start by checking
capacitors. If you are lucky, you could find a shorted tantalum.

Regards,

Laurence Motteram

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On
Behalf Of Alan Scrimgeour
Sent: Friday, 5 March 2010 11:32 AM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

The little functionality the meter had when I got it enabled me to start
a
self test, but now I can't even do that as functionality has dropped
away
rapidly. The display is fine and presumably the processor driving it,
but it
no longer responds to the keyboard.

A smell of overheating plastic after a few minutes lead me to an
LM2940CT -
5 volt regulator. It's located in the fan assisted cooling path but
getting
far too hot even allowing for that. It's output voltage is well below
5V.
It's input voltage appeared to be reasonable given it's being
overloaded, so
I conclude that either the LM2940CT is faulty or more likely, something
is
overloading its output. A circuit diagram would show me what connects to

this output so I can start searching for the culprit.

Alan

----- Original Message -----
From: "Laurence Motteram" LMotteram@scientific-devices.com.au
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Thursday, March 04, 2010 9:34 PM
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

IP issues aside, what seems to be the trouble with the 2001?

Regards,

Laurence Motteram

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com]

On

Behalf Of Alan Scrimgeour
Sent: Friday, 5 March 2010 5:47 AM
To: Discussion of precise voltage measurement
Subject: [volt-nuts] Keithley 2001 Multimeter Fault

I'm trying to repair a 7 1/2 digit Keithley Multimeter but can't get

the

circuit diagram. Keithley say they don't release schematics any more

due

to IP issues, whatever they are?

Can anyone help?

Thanks,

Alan

volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
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Don't be misled by the working display, as it has its own microprocessor. The digital PCB has two LM2940CT devices, but it sounds like the one in question supplies the digital +5V. Naturally, everything connects to this, but you might like to start by checking capacitors. If you are lucky, you could find a shorted tantalum. Regards, Laurence Motteram -----Original Message----- From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On Behalf Of Alan Scrimgeour Sent: Friday, 5 March 2010 11:32 AM To: Discussion of precise voltage measurement Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault The little functionality the meter had when I got it enabled me to start a self test, but now I can't even do that as functionality has dropped away rapidly. The display is fine and presumably the processor driving it, but it no longer responds to the keyboard. A smell of overheating plastic after a few minutes lead me to an LM2940CT - 5 volt regulator. It's located in the fan assisted cooling path but getting far too hot even allowing for that. It's output voltage is well below 5V. It's input voltage appeared to be reasonable given it's being overloaded, so I conclude that either the LM2940CT is faulty or more likely, something is overloading its output. A circuit diagram would show me what connects to this output so I can start searching for the culprit. Alan ----- Original Message ----- From: "Laurence Motteram" <LMotteram@scientific-devices.com.au> To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> Sent: Thursday, March 04, 2010 9:34 PM Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault > IP issues aside, what seems to be the trouble with the 2001? > > > Regards, > > Laurence Motteram > > -----Original Message----- > From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On > Behalf Of Alan Scrimgeour > Sent: Friday, 5 March 2010 5:47 AM > To: Discussion of precise voltage measurement > Subject: [volt-nuts] Keithley 2001 Multimeter Fault > > I'm trying to repair a 7 1/2 digit Keithley Multimeter but can't get the > circuit diagram. Keithley say they don't release schematics any more due > to IP issues, whatever they are? > > Can anyone help? > > Thanks, > > Alan > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.

AS

Alan Scrimgeour

Fri, Mar 5, 2010 1:21 AM

Thanks Laurence. Sounds like you're very familiar with the 2001?

Alan

----- Original Message -----
From: "Laurence Motteram" LMotteram@scientific-devices.com.au
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Friday, March 05, 2010 1:03 AM
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

Don't be misled by the working display, as it has its own
microprocessor. The digital PCB has two LM2940CT devices, but it sounds
like the one in question supplies the digital +5V. Naturally,
everything connects to this, but you might like to start by checking
capacitors. If you are lucky, you could find a shorted tantalum.

Regards,

Laurence Motteram

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On
Behalf Of Alan Scrimgeour
Sent: Friday, 5 March 2010 11:32 AM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

The little functionality the meter had when I got it enabled me to start
a
self test, but now I can't even do that as functionality has dropped
away
rapidly. The display is fine and presumably the processor driving it,
but it
no longer responds to the keyboard.

A smell of overheating plastic after a few minutes lead me to an
LM2940CT -
5 volt regulator. It's located in the fan assisted cooling path but
getting
far too hot even allowing for that. It's output voltage is well below
5V.
It's input voltage appeared to be reasonable given it's being
overloaded, so
I conclude that either the LM2940CT is faulty or more likely, something
is
overloading its output. A circuit diagram would show me what connects to

this output so I can start searching for the culprit.

Alan

----- Original Message -----
From: "Laurence Motteram" LMotteram@scientific-devices.com.au
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Thursday, March 04, 2010 9:34 PM
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

IP issues aside, what seems to be the trouble with the 2001?

Regards,

Laurence Motteram

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com]

On

Behalf Of Alan Scrimgeour
Sent: Friday, 5 March 2010 5:47 AM
To: Discussion of precise voltage measurement
Subject: [volt-nuts] Keithley 2001 Multimeter Fault

I'm trying to repair a 7 1/2 digit Keithley Multimeter but can't get

the

circuit diagram. Keithley say they don't release schematics any more

due

to IP issues, whatever they are?

Can anyone help?

Thanks,

Alan

volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Thanks Laurence. Sounds like you're very familiar with the 2001? Alan ----- Original Message ----- From: "Laurence Motteram" <LMotteram@scientific-devices.com.au> To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> Sent: Friday, March 05, 2010 1:03 AM Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault > Don't be misled by the working display, as it has its own > microprocessor. The digital PCB has two LM2940CT devices, but it sounds > like the one in question supplies the digital +5V. Naturally, > everything connects to this, but you might like to start by checking > capacitors. If you are lucky, you could find a shorted tantalum. > > > Regards, > > Laurence Motteram > > > -----Original Message----- > From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On > Behalf Of Alan Scrimgeour > Sent: Friday, 5 March 2010 11:32 AM > To: Discussion of precise voltage measurement > Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault > > The little functionality the meter had when I got it enabled me to start > a > self test, but now I can't even do that as functionality has dropped > away > rapidly. The display is fine and presumably the processor driving it, > but it > no longer responds to the keyboard. > > A smell of overheating plastic after a few minutes lead me to an > LM2940CT - > 5 volt regulator. It's located in the fan assisted cooling path but > getting > far too hot even allowing for that. It's output voltage is well below > 5V. > It's input voltage appeared to be reasonable given it's being > overloaded, so > I conclude that either the LM2940CT is faulty or more likely, something > is > overloading its output. A circuit diagram would show me what connects to > > this output so I can start searching for the culprit. > > Alan > > > > > ----- Original Message ----- > From: "Laurence Motteram" <LMotteram@scientific-devices.com.au> > To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> > Sent: Thursday, March 04, 2010 9:34 PM > Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault > > >> IP issues aside, what seems to be the trouble with the 2001? >> >> >> Regards, >> >> Laurence Motteram >> >> -----Original Message----- >> From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] > On >> Behalf Of Alan Scrimgeour >> Sent: Friday, 5 March 2010 5:47 AM >> To: Discussion of precise voltage measurement >> Subject: [volt-nuts] Keithley 2001 Multimeter Fault >> >> I'm trying to repair a 7 1/2 digit Keithley Multimeter but can't get > the >> circuit diagram. Keithley say they don't release schematics any more > due >> to IP issues, whatever they are? >> >> Can anyone help? >> >> Thanks, >> >> Alan >> _______________________________________________ >> volt-nuts mailing list -- volt-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> and follow the instructions there. >> >> _______________________________________________ >> volt-nuts mailing list -- volt-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> and follow the instructions there. > > > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there.

JA

John Ackermann N8UR

Fri, Mar 5, 2010 1:30 AM

Hi Chuck --

Yes, at least some of those examples would probably come under the DMCA
(not sure about an unprogrammed FPGA, because DMCA can only be used to
protect copyrightable expression and I don't know whether an
unprogrammed device would meet that test).

To the original question about making it illegal to discover
infringement, I haven't seen any cases on point, but I've had the
conversation with several software/IP lawyers and there was general
agreement that good-faith circumvention to determine infringement would
almost certainly be considered fair use.

But your original comment was that "basically, if you take a piece of
software, or hardware and figure out how it works, you have probably
violated the DMCA." And I think that way overstates the case.

John

Chuck Harris said the following on 03/04/2010 05:40 PM:

Hi John,

John Ackermann N8UR wrote:

That's a pretty substantial exaggeration of what the DMCA says. The
anticircumvention provision applies only to "technological measures"
used to control access to a "work protected under this title"

I know you are a lawyer, and I'm not, but I think DMCA applies in more ways
than you may imagine. I'll give you some examples:

I was once contracted to figure out how to use non Toshiba disk drives on
Toshiba computers. I looked in all the logical places, and with the
exception
of parts of the BIOS that were reverse engineered from IBM's, the entire
rest
of the BIOS was gibberish.

Toshiba had encrypted all of their additions to the bios to prevent them
from
being read. Their system decrypted the BIOS and loaded it into memory
where
it was run... not hard to circumvent, but it did add a layer of trickiness
to the process.

If I did this job today, I am certain that the DMCA would consider my
cracking
of the encryption routine to be circumventing a technological measure
intended
to protect the work from unauthorized access.

Once upon a time, I bought a PCB milling machine. With the machine came
original disks for the software that translated Gerber files to the CAM
files needed to mill around the circuit traces and isolate them. Somehow,
the dongle that was used in the copy protection scheme got lost, and I
figured
that I would simply circumvent it. Only thing is, the dongle was used
as an
encryption device, and substantial parts of the software on the disk were
passed through decryption routines that converted gibberish into the code
that ran in the machine.

I am certain that if I cracked that code today, I would be in violation of
the DMCA.

Another example, several, if not all of the current crop of FPGA's use a
hardware encryption routine in the chip to prevent unauthorized tools from
being able to program the chip. The manufacturers say the encryption is
there to protect the customers IP from being stolen, and perhaps it serves
that purpose.

I believe that if I were to crack the encryption algorithm, and gain access
to the customer's code, I would be in violation of the DMCA, as breaking
the
encryption would be circumventing a technological measure intended to
protect
the work from unauthorized access.

What do you think? Would these examples would be violations of the DMCA?

Ok, how does this apply? Suppose I held some patents, and I believed that
it was likely that the codes in the above examples contained infringements
of my patents. I would have to circumvent the same protection routines in
order to determine if the code, or logic contained my patented property.
If I did so, and I found infringements, could I be prosecuted for violating
the DMCA? What if I did so, and didn't find infringements?

This is my point. I believe the DMCA can protect patent infringer's from
having their infringements detected by the IP owners.

Not providing documentation on instruments further helps hide
infringements.

-Chuck Harris

volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
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and follow the instructions there.

Hi Chuck -- Yes, at least some of those examples would probably come under the DMCA (not sure about an unprogrammed FPGA, because DMCA can only be used to protect copyrightable expression and I don't know whether an unprogrammed device would meet that test). To the original question about making it illegal to discover infringement, I haven't seen any cases on point, but I've had the conversation with several software/IP lawyers and there was general agreement that good-faith circumvention to determine infringement would almost certainly be considered fair use. But your original comment was that "basically, if you take a piece of software, or hardware and figure out how it works, you have probably violated the DMCA." And I think that way overstates the case. John ---- Chuck Harris said the following on 03/04/2010 05:40 PM: > Hi John, > > John Ackermann N8UR wrote: >> That's a pretty substantial exaggeration of what the DMCA says. The >> anticircumvention provision applies only to "technological measures" >> used to control access to a "work protected under this title" > > I know you are a lawyer, and I'm not, but I think DMCA applies in more ways > than you may imagine. I'll give you some examples: > > I was once contracted to figure out how to use non Toshiba disk drives on > Toshiba computers. I looked in all the logical places, and with the > exception > of parts of the BIOS that were reverse engineered from IBM's, the entire > rest > of the BIOS was gibberish. > > Toshiba had encrypted all of their additions to the bios to prevent them > from > being read. Their system decrypted the BIOS and loaded it into memory > where > it was run... not hard to circumvent, but it did add a layer of trickiness > to the process. > > If I did this job today, I am certain that the DMCA would consider my > cracking > of the encryption routine to be circumventing a technological measure > intended > to protect the work from unauthorized access. > > Once upon a time, I bought a PCB milling machine. With the machine came > original disks for the software that translated Gerber files to the CAM > files needed to mill around the circuit traces and isolate them. Somehow, > the dongle that was used in the copy protection scheme got lost, and I > figured > that I would simply circumvent it. Only thing is, the dongle was used > as an > encryption device, and substantial parts of the software on the disk were > passed through decryption routines that converted gibberish into the code > that ran in the machine. > > I am certain that if I cracked that code today, I would be in violation of > the DMCA. > > Another example, several, if not all of the current crop of FPGA's use a > hardware encryption routine in the chip to prevent unauthorized tools from > being able to program the chip. The manufacturers say the encryption is > there to protect the customers IP from being stolen, and perhaps it serves > that purpose. > > I believe that if I were to crack the encryption algorithm, and gain access > to the customer's code, I would be in violation of the DMCA, as breaking > the > encryption would be circumventing a technological measure intended to > protect > the work from unauthorized access. > > What do you think? Would these examples would be violations of the DMCA? > > Ok, how does this apply? Suppose I held some patents, and I believed that > it was likely that the codes in the above examples contained infringements > of my patents. I would have to circumvent the same protection routines in > order to determine if the code, or logic contained my patented property. > If I did so, and I found infringements, could I be prosecuted for violating > the DMCA? What if I did so, and didn't find infringements? > > This is my point. I believe the DMCA can protect patent infringer's from > having their infringements detected by the IP owners. > > Not providing documentation on instruments further helps hide > infringements. > > -Chuck Harris > > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there.

CH

Chuck Harris

Fri, Mar 5, 2010 1:48 AM

John Ackermann N8UR wrote:

Hi Chuck --

Yes, at least some of those examples would probably come under the DMCA
(not sure about an unprogrammed FPGA, because DMCA can only be used to
protect copyrightable expression and I don't know whether an
unprogrammed device would meet that test).

I was thinking more of a programmed FPGA, but having spent some time
wondering how one could make an open source program to program an
encrypted FPGA, the unprogrammed example is also of interest.

To the original question about making it illegal to discover
infringement, I haven't seen any cases on point, but I've had the
conversation with several software/IP lawyers and there was general
agreement that good-faith circumvention to determine infringement would
almost certainly be considered fair use.

But your original comment was that "basically, if you take a piece of
software, or hardware and figure out how it works, you have probably
violated the DMCA." And I think that way overstates the case.

That's what happens when I try and keep things short and simple.

-Chuck Harris

John Ackermann N8UR wrote: > Hi Chuck -- > > Yes, at least some of those examples would probably come under the DMCA > (not sure about an unprogrammed FPGA, because DMCA can only be used to > protect copyrightable expression and I don't know whether an > unprogrammed device would meet that test). I was thinking more of a programmed FPGA, but having spent some time wondering how one could make an open source program to program an encrypted FPGA, the unprogrammed example is also of interest. > > To the original question about making it illegal to discover > infringement, I haven't seen any cases on point, but I've had the > conversation with several software/IP lawyers and there was general > agreement that good-faith circumvention to determine infringement would > almost certainly be considered fair use. > > But your original comment was that "basically, if you take a piece of > software, or hardware and figure out how it works, you have probably > violated the DMCA." And I think that way overstates the case. That's what happens when I try and keep things short and simple. -Chuck Harris

JL

John Lofgren

Fri, Mar 5, 2010 4:09 PM

Yes, check capacitors. I has something similar happen to the -5V regulator on HP 55300A GPSDO. The symptoms were very similar to your description, but with the addition of a discolored heatsink. It turned out to be a shorted ceramic cap on the regulator output.

Good luck and keep us posted.

John

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On Behalf Of Laurence Motteram
Sent: Thursday, March 04, 2010 7:04 PM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

Don't be misled by the working display, as it has its own
microprocessor. The digital PCB has two LM2940CT devices, but it sounds
like the one in question supplies the digital +5V. Naturally,
everything connects to this, but you might like to start by checking
capacitors. If you are lucky, you could find a shorted tantalum.

Regards,

Laurence Motteram

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On
Behalf Of Alan Scrimgeour
Sent: Friday, 5 March 2010 11:32 AM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

The little functionality the meter had when I got it enabled me to start
a
self test, but now I can't even do that as functionality has dropped
away
rapidly. The display is fine and presumably the processor driving it,
but it
no longer responds to the keyboard.

A smell of overheating plastic after a few minutes lead me to an
LM2940CT -
5 volt regulator. It's located in the fan assisted cooling path but
getting
far too hot even allowing for that. It's output voltage is well below
5V.
It's input voltage appeared to be reasonable given it's being
overloaded, so
I conclude that either the LM2940CT is faulty or more likely, something
is
overloading its output. A circuit diagram would show me what connects to

this output so I can start searching for the culprit.

Alan

----- Original Message -----
From: "Laurence Motteram" LMotteram@scientific-devices.com.au
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Thursday, March 04, 2010 9:34 PM
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

IP issues aside, what seems to be the trouble with the 2001?

Regards,

Laurence Motteram

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com]

On

Behalf Of Alan Scrimgeour
Sent: Friday, 5 March 2010 5:47 AM
To: Discussion of precise voltage measurement
Subject: [volt-nuts] Keithley 2001 Multimeter Fault

I'm trying to repair a 7 1/2 digit Keithley Multimeter but can't get

the

circuit diagram. Keithley say they don't release schematics any more

due

to IP issues, whatever they are?

Can anyone help?

Thanks,

Alan

volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Yes, check capacitors. I has something similar happen to the -5V regulator on HP 55300A GPSDO. The symptoms were very similar to your description, but with the addition of a discolored heatsink. It turned out to be a shorted ceramic cap on the regulator output. Good luck and keep us posted. - John -----Original Message----- From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On Behalf Of Laurence Motteram Sent: Thursday, March 04, 2010 7:04 PM To: Discussion of precise voltage measurement Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault Don't be misled by the working display, as it has its own microprocessor. The digital PCB has two LM2940CT devices, but it sounds like the one in question supplies the digital +5V. Naturally, everything connects to this, but you might like to start by checking capacitors. If you are lucky, you could find a shorted tantalum. Regards, Laurence Motteram -----Original Message----- From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On Behalf Of Alan Scrimgeour Sent: Friday, 5 March 2010 11:32 AM To: Discussion of precise voltage measurement Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault The little functionality the meter had when I got it enabled me to start a self test, but now I can't even do that as functionality has dropped away rapidly. The display is fine and presumably the processor driving it, but it no longer responds to the keyboard. A smell of overheating plastic after a few minutes lead me to an LM2940CT - 5 volt regulator. It's located in the fan assisted cooling path but getting far too hot even allowing for that. It's output voltage is well below 5V. It's input voltage appeared to be reasonable given it's being overloaded, so I conclude that either the LM2940CT is faulty or more likely, something is overloading its output. A circuit diagram would show me what connects to this output so I can start searching for the culprit. Alan ----- Original Message ----- From: "Laurence Motteram" <LMotteram@scientific-devices.com.au> To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> Sent: Thursday, March 04, 2010 9:34 PM Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault > IP issues aside, what seems to be the trouble with the 2001? > > > Regards, > > Laurence Motteram > > -----Original Message----- > From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On > Behalf Of Alan Scrimgeour > Sent: Friday, 5 March 2010 5:47 AM > To: Discussion of precise voltage measurement > Subject: [volt-nuts] Keithley 2001 Multimeter Fault > > I'm trying to repair a 7 1/2 digit Keithley Multimeter but can't get the > circuit diagram. Keithley say they don't release schematics any more due > to IP issues, whatever they are? > > Can anyone help? > > Thanks, > > Alan > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.

D

Dave

Fri, Mar 5, 2010 5:57 PM

Actually 'IP=Intellectual Property' is just two lies in one
abbreviation which only lawyers could love. The more accurate way of
looking at it is to say

   IP = Imaginary Property
   IP = Illusionary Property

Dave

Alan Scrimgeour wrote:

Ah, right: IP = Intellectual Property. I guess they might just be
worried about people stealing their design too, plus, if they can get
customers to accept not having schematics for whatever reason, they
get a monopoly on repairs.

Seems like I'm going to have to resort to reverse engineering - hope
the pcb doesn't have more than 2 layers!

Alan

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Actually 'IP=Intellectual Property' is just two lies in one abbreviation which only lawyers could love. The more accurate way of looking at it is to say IP = Imaginary Property IP = Illusionary Property Dave Alan Scrimgeour wrote: > Ah, right: IP = Intellectual Property. I guess they might just be > worried about people stealing their design too, plus, if they can get > customers to accept not having schematics for whatever reason, they > get a monopoly on repairs. > > Seems like I'm going to have to resort to reverse engineering - hope > the pcb doesn't have more than 2 layers! > > Alan > > > >> >> _______________________________________________ >> volt-nuts mailing list -- volt-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> and follow the instructions there. > > > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. >

AS

Alan Scrimgeour

Fri, Mar 5, 2010 6:15 PM

Thanks John, I plan to start the search in a few hours. Wish I had a thermal
imaging camera!

Alan

----- Original Message -----
From: "John Lofgren" jlofgren@lsr.com
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Friday, March 05, 2010 4:09 PM
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

Yes, check capacitors. I has something similar happen to the -5V
regulator on HP 55300A GPSDO. The symptoms were very similar to your
description, but with the addition of a discolored heatsink. It turned
out to be a shorted ceramic cap on the regulator output.

Good luck and keep us posted.

John

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On
Behalf Of Laurence Motteram
Sent: Thursday, March 04, 2010 7:04 PM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

Don't be misled by the working display, as it has its own
microprocessor. The digital PCB has two LM2940CT devices, but it sounds
like the one in question supplies the digital +5V. Naturally,
everything connects to this, but you might like to start by checking
capacitors. If you are lucky, you could find a shorted tantalum.

Regards,

Laurence Motteram

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On
Behalf Of Alan Scrimgeour
Sent: Friday, 5 March 2010 11:32 AM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

The little functionality the meter had when I got it enabled me to start
a
self test, but now I can't even do that as functionality has dropped
away
rapidly. The display is fine and presumably the processor driving it,
but it
no longer responds to the keyboard.

A smell of overheating plastic after a few minutes lead me to an
LM2940CT -
5 volt regulator. It's located in the fan assisted cooling path but
getting
far too hot even allowing for that. It's output voltage is well below
5V.
It's input voltage appeared to be reasonable given it's being
overloaded, so
I conclude that either the LM2940CT is faulty or more likely, something
is
overloading its output. A circuit diagram would show me what connects to

this output so I can start searching for the culprit.

Alan

----- Original Message -----
From: "Laurence Motteram" LMotteram@scientific-devices.com.au
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Thursday, March 04, 2010 9:34 PM
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

IP issues aside, what seems to be the trouble with the 2001?

Regards,

Laurence Motteram

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com]

On

Behalf Of Alan Scrimgeour
Sent: Friday, 5 March 2010 5:47 AM
To: Discussion of precise voltage measurement
Subject: [volt-nuts] Keithley 2001 Multimeter Fault

I'm trying to repair a 7 1/2 digit Keithley Multimeter but can't get

the

circuit diagram. Keithley say they don't release schematics any more

due

to IP issues, whatever they are?

Can anyone help?

Thanks,

Alan

volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Thanks John, I plan to start the search in a few hours. Wish I had a thermal imaging camera! Alan ----- Original Message ----- From: "John Lofgren" <jlofgren@lsr.com> To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> Sent: Friday, March 05, 2010 4:09 PM Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault > Yes, check capacitors. I has something similar happen to the -5V > regulator on HP 55300A GPSDO. The symptoms were very similar to your > description, but with the addition of a discolored heatsink. It turned > out to be a shorted ceramic cap on the regulator output. > > Good luck and keep us posted. > > - John > > > > > -----Original Message----- > From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On > Behalf Of Laurence Motteram > Sent: Thursday, March 04, 2010 7:04 PM > To: Discussion of precise voltage measurement > Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault > > Don't be misled by the working display, as it has its own > microprocessor. The digital PCB has two LM2940CT devices, but it sounds > like the one in question supplies the digital +5V. Naturally, > everything connects to this, but you might like to start by checking > capacitors. If you are lucky, you could find a shorted tantalum. > > > Regards, > > Laurence Motteram > > > -----Original Message----- > From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On > Behalf Of Alan Scrimgeour > Sent: Friday, 5 March 2010 11:32 AM > To: Discussion of precise voltage measurement > Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault > > The little functionality the meter had when I got it enabled me to start > a > self test, but now I can't even do that as functionality has dropped > away > rapidly. The display is fine and presumably the processor driving it, > but it > no longer responds to the keyboard. > > A smell of overheating plastic after a few minutes lead me to an > LM2940CT - > 5 volt regulator. It's located in the fan assisted cooling path but > getting > far too hot even allowing for that. It's output voltage is well below > 5V. > It's input voltage appeared to be reasonable given it's being > overloaded, so > I conclude that either the LM2940CT is faulty or more likely, something > is > overloading its output. A circuit diagram would show me what connects to > > this output so I can start searching for the culprit. > > Alan > > > > > ----- Original Message ----- > From: "Laurence Motteram" <LMotteram@scientific-devices.com.au> > To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> > Sent: Thursday, March 04, 2010 9:34 PM > Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault > > >> IP issues aside, what seems to be the trouble with the 2001? >> >> >> Regards, >> >> Laurence Motteram >> >> -----Original Message----- >> From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] > On >> Behalf Of Alan Scrimgeour >> Sent: Friday, 5 March 2010 5:47 AM >> To: Discussion of precise voltage measurement >> Subject: [volt-nuts] Keithley 2001 Multimeter Fault >> >> I'm trying to repair a 7 1/2 digit Keithley Multimeter but can't get > the >> circuit diagram. Keithley say they don't release schematics any more > due >> to IP issues, whatever they are? >> >> Can anyone help? >> >> Thanks, >> >> Alan >> _______________________________________________ >> volt-nuts mailing list -- volt-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> and follow the instructions there. >> >> _______________________________________________ >> volt-nuts mailing list -- volt-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> and follow the instructions there. > > > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there.

BC

Brooke Clarke

Fri, Mar 5, 2010 7:13 PM

Hi Alan:

I have a bunch of combined capacitance and ESR meters that I'm about to
start selling. See:
http://www.prc68.com/I/ESRmicro.shtml

Have Fun,

Brooke Clarke
http://www.PRC68.com

Alan Scrimgeour wrote:

Thanks John, I plan to start the search in a few hours. Wish I had a
thermal imaging camera!

Alan

----- Original Message ----- From: "John Lofgren" jlofgren@lsr.com
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Friday, March 05, 2010 4:09 PM
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

Yes, check capacitors. I has something similar happen to the -5V
regulator on HP 55300A GPSDO. The symptoms were very similar to your
description, but with the addition of a discolored heatsink. It
turned out to be a shorted ceramic cap on the regulator output.

Good luck and keep us posted.

John

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com]
On Behalf Of Laurence Motteram
Sent: Thursday, March 04, 2010 7:04 PM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

Don't be misled by the working display, as it has its own
microprocessor. The digital PCB has two LM2940CT devices, but it sounds
like the one in question supplies the digital +5V. Naturally,
everything connects to this, but you might like to start by checking
capacitors. If you are lucky, you could find a shorted tantalum.

Regards,

Laurence Motteram

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On
Behalf Of Alan Scrimgeour
Sent: Friday, 5 March 2010 11:32 AM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

The little functionality the meter had when I got it enabled me to start
a
self test, but now I can't even do that as functionality has dropped
away
rapidly. The display is fine and presumably the processor driving it,
but it
no longer responds to the keyboard.

A smell of overheating plastic after a few minutes lead me to an
LM2940CT -
5 volt regulator. It's located in the fan assisted cooling path but
getting
far too hot even allowing for that. It's output voltage is well below
5V.
It's input voltage appeared to be reasonable given it's being
overloaded, so
I conclude that either the LM2940CT is faulty or more likely, something
is
overloading its output. A circuit diagram would show me what connects to

this output so I can start searching for the culprit.

Alan

----- Original Message ----- From: "Laurence Motteram"
LMotteram@scientific-devices.com.au
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Thursday, March 04, 2010 9:34 PM
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

IP issues aside, what seems to be the trouble with the 2001?

Regards,

Laurence Motteram

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com]

On

Behalf Of Alan Scrimgeour
Sent: Friday, 5 March 2010 5:47 AM
To: Discussion of precise voltage measurement
Subject: [volt-nuts] Keithley 2001 Multimeter Fault

I'm trying to repair a 7 1/2 digit Keithley Multimeter but can't get

the

circuit diagram. Keithley say they don't release schematics any more

due

to IP issues, whatever they are?

Can anyone help?

Thanks,

Alan

volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Hi Alan: I have a bunch of combined capacitance and ESR meters that I'm about to start selling. See: http://www.prc68.com/I/ESRmicro.shtml Have Fun, Brooke Clarke http://www.PRC68.com Alan Scrimgeour wrote: > Thanks John, I plan to start the search in a few hours. Wish I had a > thermal imaging camera! > > Alan > > > ----- Original Message ----- From: "John Lofgren" <jlofgren@lsr.com> > To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> > Sent: Friday, March 05, 2010 4:09 PM > Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault > > >> Yes, check capacitors. I has something similar happen to the -5V >> regulator on HP 55300A GPSDO. The symptoms were very similar to your >> description, but with the addition of a discolored heatsink. It >> turned out to be a shorted ceramic cap on the regulator output. >> >> Good luck and keep us posted. >> >> - John >> >> >> >> >> -----Original Message----- >> From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] >> On Behalf Of Laurence Motteram >> Sent: Thursday, March 04, 2010 7:04 PM >> To: Discussion of precise voltage measurement >> Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault >> >> Don't be misled by the working display, as it has its own >> microprocessor. The digital PCB has two LM2940CT devices, but it sounds >> like the one in question supplies the digital +5V. Naturally, >> everything connects to this, but you might like to start by checking >> capacitors. If you are lucky, you could find a shorted tantalum. >> >> >> Regards, >> >> Laurence Motteram >> >> >> -----Original Message----- >> From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On >> Behalf Of Alan Scrimgeour >> Sent: Friday, 5 March 2010 11:32 AM >> To: Discussion of precise voltage measurement >> Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault >> >> The little functionality the meter had when I got it enabled me to start >> a >> self test, but now I can't even do that as functionality has dropped >> away >> rapidly. The display is fine and presumably the processor driving it, >> but it >> no longer responds to the keyboard. >> >> A smell of overheating plastic after a few minutes lead me to an >> LM2940CT - >> 5 volt regulator. It's located in the fan assisted cooling path but >> getting >> far too hot even allowing for that. It's output voltage is well below >> 5V. >> It's input voltage appeared to be reasonable given it's being >> overloaded, so >> I conclude that either the LM2940CT is faulty or more likely, something >> is >> overloading its output. A circuit diagram would show me what connects to >> >> this output so I can start searching for the culprit. >> >> Alan >> >> >> >> >> ----- Original Message ----- From: "Laurence Motteram" >> <LMotteram@scientific-devices.com.au> >> To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> >> Sent: Thursday, March 04, 2010 9:34 PM >> Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault >> >> >>> IP issues aside, what seems to be the trouble with the 2001? >>> >>> >>> Regards, >>> >>> Laurence Motteram >>> >>> -----Original Message----- >>> From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] >> On >>> Behalf Of Alan Scrimgeour >>> Sent: Friday, 5 March 2010 5:47 AM >>> To: Discussion of precise voltage measurement >>> Subject: [volt-nuts] Keithley 2001 Multimeter Fault >>> >>> I'm trying to repair a 7 1/2 digit Keithley Multimeter but can't get >> the >>> circuit diagram. Keithley say they don't release schematics any more >> due >>> to IP issues, whatever they are? >>> >>> Can anyone help? >>> >>> Thanks, >>> >>> Alan >>> _______________________________________________ >>> volt-nuts mailing list -- volt-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >>> and follow the instructions there. >>> >>> _______________________________________________ >>> volt-nuts mailing list -- volt-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >>> and follow the instructions there. >> >> >> >> _______________________________________________ >> volt-nuts mailing list -- volt-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> and follow the instructions there. >> >> _______________________________________________ >> volt-nuts mailing list -- volt-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> and follow the instructions there. >> >> _______________________________________________ >> volt-nuts mailing list -- volt-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> and follow the instructions there. > > > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > >

AS

Alan Scrimgeour

Fri, Mar 5, 2010 7:41 PM

I just had another look at the Keithley 2001:
At power on the display shows "Model 2001" etc., followed by "Autoranging
DCV", with a row of dashes above it where the digits should be. Perhaps this
is all just the display processor at work.

I can see that the upper PCB and the lower PCB each have an LM2940CT-5. The
overheating one is on the upper PCB which has all the analogue circuitry on
it. I can't immediately see how to get the analogue PCB out without major
surgery and prefer not to risk contaminating it yet so I've just probed
around measuring resistance from the LM2940CT-5 output to accessible
capacitors positive terminals. I get 0.2 Ohms to pin 16 of a few digital
looking IC's, but nothing to any of the capacitors so I guess I'm going to
have to get the PCB out...

Alan

----- Original Message -----
From: "Laurence Motteram" LMotteram@scientific-devices.com.au
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Friday, March 05, 2010 1:03 AM
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

Don't be misled by the working display, as it has its own
microprocessor. The digital PCB has two LM2940CT devices, but it sounds
like the one in question supplies the digital +5V. Naturally,
everything connects to this, but you might like to start by checking
capacitors. If you are lucky, you could find a shorted tantalum.

Regards,

Laurence Motteram

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On
Behalf Of Alan Scrimgeour
Sent: Friday, 5 March 2010 11:32 AM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

The little functionality the meter had when I got it enabled me to start
a
self test, but now I can't even do that as functionality has dropped
away
rapidly. The display is fine and presumably the processor driving it,
but it
no longer responds to the keyboard.

A smell of overheating plastic after a few minutes lead me to an
LM2940CT -
5 volt regulator. It's located in the fan assisted cooling path but
getting
far too hot even allowing for that. It's output voltage is well below
5V.
It's input voltage appeared to be reasonable given it's being
overloaded, so
I conclude that either the LM2940CT is faulty or more likely, something
is
overloading its output. A circuit diagram would show me what connects to

this output so I can start searching for the culprit.

Alan

----- Original Message -----
From: "Laurence Motteram" LMotteram@scientific-devices.com.au
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Thursday, March 04, 2010 9:34 PM
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

IP issues aside, what seems to be the trouble with the 2001?

Regards,

Laurence Motteram

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com]

On

Behalf Of Alan Scrimgeour
Sent: Friday, 5 March 2010 5:47 AM
To: Discussion of precise voltage measurement
Subject: [volt-nuts] Keithley 2001 Multimeter Fault

I'm trying to repair a 7 1/2 digit Keithley Multimeter but can't get

the

circuit diagram. Keithley say they don't release schematics any more

due

to IP issues, whatever they are?

Can anyone help?

Thanks,

Alan

volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

I just had another look at the Keithley 2001: At power on the display shows "Model 2001" etc., followed by "Autoranging DCV", with a row of dashes above it where the digits should be. Perhaps this is all just the display processor at work. I can see that the upper PCB and the lower PCB each have an LM2940CT-5. The overheating one is on the upper PCB which has all the analogue circuitry on it. I can't immediately see how to get the analogue PCB out without major surgery and prefer not to risk contaminating it yet so I've just probed around measuring resistance from the LM2940CT-5 output to accessible capacitors positive terminals. I get 0.2 Ohms to pin 16 of a few digital looking IC's, but nothing to any of the capacitors so I guess I'm going to have to get the PCB out... Alan ----- Original Message ----- From: "Laurence Motteram" <LMotteram@scientific-devices.com.au> To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> Sent: Friday, March 05, 2010 1:03 AM Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault > Don't be misled by the working display, as it has its own > microprocessor. The digital PCB has two LM2940CT devices, but it sounds > like the one in question supplies the digital +5V. Naturally, > everything connects to this, but you might like to start by checking > capacitors. If you are lucky, you could find a shorted tantalum. > > > Regards, > > Laurence Motteram > > > -----Original Message----- > From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On > Behalf Of Alan Scrimgeour > Sent: Friday, 5 March 2010 11:32 AM > To: Discussion of precise voltage measurement > Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault > > The little functionality the meter had when I got it enabled me to start > a > self test, but now I can't even do that as functionality has dropped > away > rapidly. The display is fine and presumably the processor driving it, > but it > no longer responds to the keyboard. > > A smell of overheating plastic after a few minutes lead me to an > LM2940CT - > 5 volt regulator. It's located in the fan assisted cooling path but > getting > far too hot even allowing for that. It's output voltage is well below > 5V. > It's input voltage appeared to be reasonable given it's being > overloaded, so > I conclude that either the LM2940CT is faulty or more likely, something > is > overloading its output. A circuit diagram would show me what connects to > > this output so I can start searching for the culprit. > > Alan > > > > > ----- Original Message ----- > From: "Laurence Motteram" <LMotteram@scientific-devices.com.au> > To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> > Sent: Thursday, March 04, 2010 9:34 PM > Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault > > >> IP issues aside, what seems to be the trouble with the 2001? >> >> >> Regards, >> >> Laurence Motteram >> >> -----Original Message----- >> From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] > On >> Behalf Of Alan Scrimgeour >> Sent: Friday, 5 March 2010 5:47 AM >> To: Discussion of precise voltage measurement >> Subject: [volt-nuts] Keithley 2001 Multimeter Fault >> >> I'm trying to repair a 7 1/2 digit Keithley Multimeter but can't get > the >> circuit diagram. Keithley say they don't release schematics any more > due >> to IP issues, whatever they are? >> >> Can anyone help? >> >> Thanks, >> >> Alan >> _______________________________________________ >> volt-nuts mailing list -- volt-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> and follow the instructions there. >> >> _______________________________________________ >> volt-nuts mailing list -- volt-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> and follow the instructions there. > > > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there.

EP

Ed Palmer

Fri, Mar 5, 2010 8:37 PM

Do you have another meter with enough resolution that you could trace
the voltage drops to find the bad component? i.e. lowest voltage
reading would be right next to the shorted component or highest voltage
drop would be between the regulator output and the shorted component.

Ed

Alan Scrimgeour wrote:

I just had another look at the Keithley 2001:
At power on the display shows "Model 2001" etc., followed by
"Autoranging DCV", with a row of dashes above it where the digits
should be. Perhaps this is all just the display processor at work.

I can see that the upper PCB and the lower PCB each have an
LM2940CT-5. The overheating one is on the upper PCB which has all the
analogue circuitry on it. I can't immediately see how to get the
analogue PCB out without major surgery and prefer not to risk
contaminating it yet so I've just probed around measuring resistance
from the LM2940CT-5 output to accessible capacitors positive
terminals. I get 0.2 Ohms to pin 16 of a few digital looking IC's, but
nothing to any of the capacitors so I guess I'm going to have to get
the PCB out...

Alan

----- Original Message ----- From: "Laurence Motteram"
LMotteram@scientific-devices.com.au
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Friday, March 05, 2010 1:03 AM
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

Don't be misled by the working display, as it has its own
microprocessor. The digital PCB has two LM2940CT devices, but it sounds
like the one in question supplies the digital +5V. Naturally,
everything connects to this, but you might like to start by checking
capacitors. If you are lucky, you could find a shorted tantalum.

Regards,

Laurence Motteram

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On
Behalf Of Alan Scrimgeour
Sent: Friday, 5 March 2010 11:32 AM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault

The little functionality the meter had when I got it enabled me to
start a
self test, but now I can't even do that as functionality has dropped
away
rapidly. The display is fine and presumably the processor driving it,
but it no longer responds to the keyboard.

A smell of overheating plastic after a few minutes lead me to an
LM2940CT -
5 volt regulator. It's located in the fan assisted cooling path but
getting
far too hot even allowing for that. It's output voltage is well below
5V.
It's input voltage appeared to be reasonable given it's being
overloaded, so
I conclude that either the LM2940CT is faulty or more likely,
something is
overloading its output. A circuit diagram would show me what connects to
this output so I can start searching for the culprit.

Alan

Do you have another meter with enough resolution that you could trace the voltage drops to find the bad component? i.e. lowest voltage reading would be right next to the shorted component or highest voltage drop would be between the regulator output and the shorted component. Ed Alan Scrimgeour wrote: > I just had another look at the Keithley 2001: > At power on the display shows "Model 2001" etc., followed by > "Autoranging DCV", with a row of dashes above it where the digits > should be. Perhaps this is all just the display processor at work. > > I can see that the upper PCB and the lower PCB each have an > LM2940CT-5. The overheating one is on the upper PCB which has all the > analogue circuitry on it. I can't immediately see how to get the > analogue PCB out without major surgery and prefer not to risk > contaminating it yet so I've just probed around measuring resistance > from the LM2940CT-5 output to accessible capacitors positive > terminals. I get 0.2 Ohms to pin 16 of a few digital looking IC's, but > nothing to any of the capacitors so I guess I'm going to have to get > the PCB out... > > Alan > > > > ----- Original Message ----- From: "Laurence Motteram" > <LMotteram@scientific-devices.com.au> > To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> > Sent: Friday, March 05, 2010 1:03 AM > Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault > > >> Don't be misled by the working display, as it has its own >> microprocessor. The digital PCB has two LM2940CT devices, but it sounds >> like the one in question supplies the digital +5V. Naturally, >> everything connects to this, but you might like to start by checking >> capacitors. If you are lucky, you could find a shorted tantalum. >> >> >> Regards, >> >> Laurence Motteram >> >> >> -----Original Message----- >> From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On >> Behalf Of Alan Scrimgeour >> Sent: Friday, 5 March 2010 11:32 AM >> To: Discussion of precise voltage measurement >> Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault >> >> The little functionality the meter had when I got it enabled me to >> start a >> self test, but now I can't even do that as functionality has dropped >> away >> rapidly. The display is fine and presumably the processor driving it, >> but it no longer responds to the keyboard. >> >> A smell of overheating plastic after a few minutes lead me to an >> LM2940CT - >> 5 volt regulator. It's located in the fan assisted cooling path but >> getting >> far too hot even allowing for that. It's output voltage is well below >> 5V. >> It's input voltage appeared to be reasonable given it's being >> overloaded, so >> I conclude that either the LM2940CT is faulty or more likely, >> something is >> overloading its output. A circuit diagram would show me what connects to >> this output so I can start searching for the culprit. >> >> Alan

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Keithley 2001 Multimeter Fault

John