3458A reference boards on ebay
I think teletekjm23@gmail.com has some that were removed from working unit
to upgrade to the more stable board.
On Wed, Jan 28, 2015 at 7:07 PM, Randy Evans randyevans2688@gmail.com
wrote:
I bought two HP-3458A ref boards from John Daly (he no longer has any more)
and they worked fine but have intermittent noise bursts. I suspect they
were rejects from HP/Agilent. At some point I will probably replace the
LTZ1000As and reduce the internal temperature set point for better
stability. Has anyone else had any issues with these units?
BTW, I packaged the units in an enclosure for a stand-alone reference and,
except for the occasional noise bursts, seem very stable according to my HP
3458A and fluke 732A/ESI RV722 KVD.
Randy
On Wed, Jan 28, 2015 at 9:40 AM, John Phillips john.phillips0@gmail.com
wrote:
There is a bottom cover under the board.
On Tue, Jan 27, 2015 at 9:01 PM, J. L. Trantham jltran@att.net wrote:
When these boards are installed in a 3458A, the LTZ1000 is covered by a
small, white, 'hat' that mounts with screws that pass through the two
holes
on opposite sides of the LTZ1000. I've never removed the board to see
if
there is anything on the bottom of the board that would cover the
bottom
of
the LTZ1000.
Does anyone know what this 'hat' is constructed of or the
HP/Agilent/Keysight part number of this item is? Is it available from
Keysight?
In the 3458A the reference board is under a cover that covers about
half
of the top of the meter but not 'insulated' beyond that, except for the
'hat' referred to above.
It would appear desirable to find what that 'hat' is and see if
something
could be fabricated to 'insulate' the LTZ1000 for a 'do it yourself'
standalone reference.
Would appreciate hearing anything about how the reference board is
'insulated' in the 3458A.
Thanks.
Joe
-----Original Message-----
From: volt-nuts [mailto:volt-nuts-bounces@febo.com] On Behalf Of Orin
Eman
Sent: Tuesday, January 27, 2015 11:45 AM
To: Discussion of precise voltage measurement
Subject: [Bulk] Re: [volt-nuts] 3458A reference boards on ebay
Dave,
I'll be putting it in an enclosure to use as a reference. It will
probably be a smallish diecast aluminium box. It's what I did with my
Geller SVR-T and it compared very well with my Fluke 731B. I'll likely
use
Pomona 3770 binding posts for output (I used them to repair the 731B).
I'll also use the protection circuits from the Fluke 732 on the output
big reverse diode, gas discharge tube and TVS as I recall (I plan to
add
these protection circuits to the 731B).
I'll likely do a PCB for it, though the local equivalent of veroboard
would likely be OK; the socket spacing is 0.9" and the pin spacing
0.1".
My meters are also 6 1/2 digit (3456A and 34461A) so I'm not too
concerned
with thermal EMFs with one count being 10uV on the 10V range.
However, I
will try to avoid temperature gradients and keep the outputs close
together. I'll use star wiring for the 18V and ground as in the
following:
http://www.maxmcarter.com/vref/
It is debatable whether the -15V supply is needed - I'll test with and
without. I'd add a few tantalum capacitors to the above design - on
the
regulator outputs and on the 3320 resistor, along with protection
diodes
for the LM317.
There is also a HUGE thread about the LTZ1000 on EEVBlog - I'll be
reviewing that for ideas:
I actually have a couple of LTZ1000As here that I was going to DIY, but
never got around to getting the precision resisters . I think there
is a
source in England mentioned in the EEVBlog thread.
Orin.
On Tue, Jan 27, 2015 at 2:24 AM, Dr. David Kirkby (Kirkby Microwave
Ltd)
<
drkirkby@kirkbymicrowave.co.uk> wrote:
On 27 January 2015 at 09:16, Orin Eman orin.eman@gmail.com wrote:
There is a seller letting a slow trickle of them out there... they
seem
to
be going for about $165. The current batch of two is around $100,
but
will
probably be bid up.
I just received one that I won. Seems to be working fine after a
quick breadboard lashup. I'll be making an enclosure for it next.
A little expensive IMO, but given the trouble getting the precision
resistors to DIY with the LTZ1000A, probably worth it.
Orin
Orin,
What do you intend doing with it?
I was thinking about getting one of those, with a view to putting it
in a box with a couple of terminals to have something to compare with
my 6.5 digit 3457A. But what put me off is a lack of knowledge in
knowing how to convert a 3458A reference board into a boxed unit with
a known output voltage at the terminals. How would I avoid / control
thermal EMFs?
I'd be interested to hear what your plans are for it, and how you
intend tackling those issues.
Do you know what the difference in the reference is between a
standard
3458A (8 ppm) and the high stability option 002 (4 ppm) model? I'm
guessing the chips for the option 002 might be the top performing
ones. I wonder if there's any way to tell from your board if it came
from a standard 3458A or a 3458A with option 002.
Dave
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John Phillips
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Am 29.01.2015 04:07, schrieb Randy Evans:
I bought two HP-3458A ref boards from John Daly (he no longer has any more)
and they worked fine but have intermittent noise bursts. I suspect they
were rejects from HP/Agilent. At some point I will probably replace the
LTZ1000As and reduce the internal temperature set point for better
stability. Has anyone else had any issues with these units?
BTW, I packaged the units in an enclosure for a stand-alone reference and,
except for the occasional noise bursts, seem very stable according to my HP
3458A and fluke 732A/ESI RV722 KVD.
Randy
Hi Randy,
Noise bursts, especially if they get back on track again, sound like
electromagnetic interference from your short description.
If applicable, turn of the CFL or LED lighting, replace the switch-mode
power supply with a linear one or even better a battery,, try a known
non-reject in place of the ebay reference module, spread some capacitors
on/around the module and/or invest in a metal box.
Hendrik
The reference module is in a metal box and uses an external linear PS with
internal separate regulation. I don't think its external EMI, but anything
is possible.
Randy
On Wed, Jan 28, 2015 at 10:28 PM, Hendrik Dietrich don_hendi@gmx.de wrote:
Am 29.01.2015 04:07, schrieb Randy Evans:
I bought two HP-3458A ref boards from John Daly (he no longer has any
more)
and they worked fine but have intermittent noise bursts. I suspect they
were rejects from HP/Agilent. At some point I will probably replace the
LTZ1000As and reduce the internal temperature set point for better
stability. Has anyone else had any issues with these units?
BTW, I packaged the units in an enclosure for a stand-alone reference and,
except for the occasional noise bursts, seem very stable according to my
HP
3458A and fluke 732A/ESI RV722 KVD.
Randy
Hi Randy,
Noise bursts, especially if they get back on track again, sound like
electromagnetic interference from your short description.
If applicable, turn of the CFL or LED lighting, replace the switch-mode
power supply with a linear one or even better a battery,, try a known
non-reject in place of the ebay reference module, spread some capacitors
on/around the module and/or invest in a metal box.
Hendrik
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mailman/listinfo/volt-nuts
and follow the instructions there.
Well, sounds like you already prepared against some of my suggestions.
Still there are possibilities to troubleshoot it - i cannot neither see
that you checked everything I listed nor that my list is complete and
you had much bigger ideas.
The datasheet gives some figures telling how much some influences, like
R variations (and as a result I variations) get supressed on the output -
I would go hunting for nodes where the noise bursts are biggest if all
preventive actions failed. Up to a certain point, troubleshooting is fun.
Hendrik
Am 29.01.2015 18:22, schrieb Randy Evans:
The reference module is in a metal box and uses an external linear PS with
internal separate regulation. I don't think its external EMI, but anything
is possible.
Randy
On Wed, Jan 28, 2015 at 10:28 PM, Hendrik Dietrich don_hendi@gmx.de wrote:
Am 29.01.2015 04:07, schrieb Randy Evans:
I bought two HP-3458A ref boards from John Daly (he no longer has any
more)
and they worked fine but have intermittent noise bursts. I suspect they
were rejects from HP/Agilent. At some point I will probably replace the
LTZ1000As and reduce the internal temperature set point for better
stability. Has anyone else had any issues with these units?
BTW, I packaged the units in an enclosure for a stand-alone reference and,
except for the occasional noise bursts, seem very stable according to my
HP
3458A and fluke 732A/ESI RV722 KVD.
Randy
Hi Randy,
Noise bursts, especially if they get back on track again, sound like
electromagnetic interference from your short description.
If applicable, turn of the CFL or LED lighting, replace the switch-mode
power supply with a linear one or even better a battery, try a known
non-reject in place of the ebay reference module, spread some capacitors
on/around the module and/or invest in a metal box.
Hendrik
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On 27 Jan 2015 09:47, "Orin Eman" orin.eman@gmail.com wrote:
There is a seller letting a slow trickle of them out there... they seem to
be going for about $165. The current batch of two is around $100, but
will
probably be bid up.
I am puzzled why there are so many reference boards that are supposed to
come from 3458As on the used market. It makes me wonder if they are
genuine.
One seller, with the two high stability reference boards at $750, claims
that they come from working and recently calibrated 3458As. Why would
anyone wreck a working and recently calibrated 3458A?
It is not beyond the bounds of possibility that a 3458A might be worth more
in parts than as a complete unit. I know this is true for some HP items,
but I doubt that is the case with a 3458A.
Another seller, who has them at $395 "or offer", has sold 17 and has 11
left.
Although expensive, having two and monitoring the difference between them
would probably allow their stability to be measured with a DVM of modest
specification.
There are lots of counterfeit components around, and I fear that it could
be some of these boards could fall into that category. This makes the
building a board from new components more attractive. In the short term it
is likely to be less stable than an old reference, but at least one would
know the history of it. If the components were sourced from reliable
sources, it would get around the potential counterfeit problem.
Dave.
RE: "One seller, with the two high stability reference boards at $750,
claims
that they come from working and recently calibrated 3458As. Why would
anyone wreck a working and recently calibrated 3458A?
"
Some contracts may require the more stable reference and the standard
reference is pulled to make room for the option 002.
I know I have done that at lest 30 times.
On Thu, Jan 29, 2015 at 12:59 PM, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkirkby@kirkbymicrowave.co.uk> wrote:
On 27 Jan 2015 09:47, "Orin Eman" orin.eman@gmail.com wrote:
There is a seller letting a slow trickle of them out there... they seem
to
be going for about $165. The current batch of two is around $100, but
will
probably be bid up.
I am puzzled why there are so many reference boards that are supposed to
come from 3458As on the used market. It makes me wonder if they are
genuine.
One seller, with the two high stability reference boards at $750, claims
that they come from working and recently calibrated 3458As. Why would
anyone wreck a working and recently calibrated 3458A?
It is not beyond the bounds of possibility that a 3458A might be worth more
in parts than as a complete unit. I know this is true for some HP items,
but I doubt that is the case with a 3458A.
Another seller, who has them at $395 "or offer", has sold 17 and has 11
left.
Although expensive, having two and monitoring the difference between them
would probably allow their stability to be measured with a DVM of modest
specification.
There are lots of counterfeit components around, and I fear that it could
be some of these boards could fall into that category. This makes the
building a board from new components more attractive. In the short term it
is likely to be less stable than an old reference, but at least one would
know the history of it. If the components were sourced from reliable
sources, it would get around the potential counterfeit problem.
Dave.
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--
John Phillips
The boards are factory rejects.
I bought five of them several years ago when the price was around $40.
One of them had the heater transistor flipped. Worked fine after
reversing the transistor. One had misaligned connector, which would
have been easy to repair but the HP policy seems to be reject rather
than repair small boards. One had corner of the Vishay resistor
cracked.
Two of them were cosmetically perfect but had much higher noise than others.
Be prepared that there is always something wrong. Could be a good idea
to prefer those with some obvious cosmetic problem...
I am puzzled why there are so many reference boards that are supposed to
come from 3458As on the used market. It makes me wonder if they are
genuine.
One seller, with the two high stability reference boards at $750, claims
that they come from working and recently calibrated 3458As. Why would
anyone wreck a working and recently calibrated 3458A?
It is not beyond the bounds of possibility that a 3458A might be worth more
in parts than as a complete unit. I know this is true for some HP items,
but I doubt that is the case with a 3458A.
Another seller, who has them at $395 "or offer", has sold 17 and has 11
left.
Although expensive, having two and monitoring the difference between them
would probably allow their stability to be measured with a DVM of modest
specification.
There are lots of counterfeit components around, and I fear that it could
be some of these boards could fall into that category. This makes the
building a board from new components more attractive. In the short term it
is likely to be less stable than an old reference, but at least one would
know the history of it. If the components were sourced from reliable
sources, it would get around the potential counterfeit problem.
Dave.
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and follow the instructions there.
On 30 January 2015 at 12:25, Will willvolts@gmail.com wrote:
The boards are factory rejects.
I doubt all boards on eBay are in this category. Some are probably
quite genuine, some may be rejects, and it would never surprise me if
some are counterfeit. The problem is, I have no idea what ones are
what.
I don't know what the problems sourcing the parts for making a
reference would be, but if a number of people wanted to make one from
parts, perhaps someone could produce a PCB and people contribute
towards the cost of it. Maybe leave people to get their own reference
chip, as there are different grades of that. But things like the
precision resistors may be easier to buy in a quantity of 10 rather
than 1.
I would certainly not mind buying one if a PCB was available. Even if
it works out costing a bit more than a 3458A reference from eBay, I'd
feel a bit happier.
Dave
There is currently a thread on EEVBlog where one has already been built. I
believe it can be purchased once the final layout is completed.
http://www.eevblog.com/forum/projects/project-kx-diy-calibrator-reference-sourcemeter/
Todd
On Fri, Jan 30, 2015 at 8:24 AM, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkirkby@kirkbymicrowave.co.uk> wrote:
On 30 January 2015 at 12:25, Will willvolts@gmail.com wrote:
The boards are factory rejects.
I doubt all boards on eBay are in this category. Some are probably
quite genuine, some may be rejects, and it would never surprise me if
some are counterfeit. The problem is, I have no idea what ones are
what.
I don't know what the problems sourcing the parts for making a
reference would be, but if a number of people wanted to make one from
parts, perhaps someone could produce a PCB and people contribute
towards the cost of it. Maybe leave people to get their own reference
chip, as there are different grades of that. But things like the
precision resistors may be easier to buy in a quantity of 10 rather
than 1.
I would certainly not mind buying one if a PCB was available. Even if
it works out costing a bit more than a 3458A reference from eBay, I'd
feel a bit happier.
Dave
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and follow the instructions there.
I'd go for a deal like that as well. I have a small number of LM399s that
I'd like to put to use, as well as a couple LTZ1000A references. A project
using either type of reference would be very exciting for me.
I have a few old Fluke differential meters that have lots of nice low
tempco, high quality resistors that might finally find a useful project such
as this.
Count me in,
Dave M.
Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
On 30 January 2015 at 12:25, Will willvolts@gmail.com wrote:
The boards are factory rejects.
I doubt all boards on eBay are in this category. Some are probably
quite genuine, some may be rejects, and it would never surprise me if
some are counterfeit. The problem is, I have no idea what ones are
what.
I don't know what the problems sourcing the parts for making a
reference would be, but if a number of people wanted to make one from
parts, perhaps someone could produce a PCB and people contribute
towards the cost of it. Maybe leave people to get their own reference
chip, as there are different grades of that. But things like the
precision resistors may be easier to buy in a quantity of 10 rather
than 1.
I would certainly not mind buying one if a PCB was available. Even if
it works out costing a bit more than a 3458A reference from eBay, I'd
feel a bit happier.
Dave