3458A AC board
First thing to do is get the meter in and to try and debug the AC board. It could be something as simple as a flakey connection or bad cap/diode/transistor/moon phase modulator.
If you have a (very good) friend with another 3458A it would be good to try swapping the AC board to verify that is actually the problem.
Next I would probably get the component level documentation try to debug the unit with that info.
Only then would I spring for a new AC board (or probably just let HP fix the thing). It would not be good to buy a $1000 board that does not fix the problem...
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Okay, it arrived a few days ago. Its pretty banged up on the outside and obviously lived a pretty hard life, but it looks pristine on the inside.
All of the connections look good and the voltages on the inguard power supply are fine. The only thing that I've found is what appears to be a blown fuse. There are two soldered-on fuses on the AC board: F701 seems okay (ohm meter sees a short), F702 is open (blown). Anyone have an idea what this fuse is for?
There are three additional fuses (F001, F002, and F003) on the AC board near a silkscreen label "SPARE FUSES". Are these truly spares? Are there any special precautions that I should take before swapping out the bad fuse for one of the spares?
Randy.
--- On Tue, 8/18/09, Mark Sims holrum@hotmail.com wrote:
From: Mark Sims holrum@hotmail.com
Subject: [volt-nuts] 3458A AC board
To: volt-nuts@febo.com
Date: Tuesday, August 18, 2009, 12:47 PM
First thing to do is get the meter in and to try and debug
the AC board. It could be something as simple as a
flakey connection or bad cap/diode/transistor/moon phase
modulator.
If you have a (very good) friend with another 3458A it
would be good to try swapping the AC board to verify that is
actually the problem.
Next I would probably get the component level
documentation try to debug the unit with that info.
Only then would I spring for a new AC board (or probably
just let HP fix the thing). It would not be good to
buy a $1000 board that does not fix the problem...
With Windows Live, you can organize, edit, and share your
photos.
http://www.windowslive.com/Desktop/PhotoGallery
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Randy wrote:
There are two soldered-on fuses on the AC board: F701 seems okay (ohm meter
sees a short), F702 is open (blown). Anyone have an idea what this fuse is
for?
--------clip--------
Randy, F702 is a 0.125A fuse between raw -18V and the collector of Q702,
which is the -17V regulator. So I'd first measure the resistance from board
ground to the emitter of Q702. It it's a short (or nearly so), you'd want to
follow the -17V line to see what's holding it down. First thing to look at
would be the 15uF capacitor (C709) running from the emitter of Q702 to
ground.
F001, F002 and F003 are indeed spare fuses, so you can use one of them to
replace F702.
Let us know what you find.
Greg
Greg,
Thanks for the information. However, it was actually F701 (my bad) that was blown. Taking a chance, I jumpered it to one of the spares and it seems to be running great. It seems too easy... :)
Randy.
--- On Wed, 8/26/09, Greg Burnett gbusg@comcast.net wrote:
From: Greg Burnett gbusg@comcast.net
Subject: Re: [volt-nuts] 3458A AC board
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Date: Wednesday, August 26, 2009, 11:24 AM
Randy wrote:
There are two soldered-on fuses on the AC board: F701 seems
okay (ohm meter
sees a short), F702 is open (blown). Anyone have an
idea what this fuse is
for?
--------clip--------
Randy, F702 is a 0.125A fuse between raw -18V and the
collector of Q702,
which is the -17V regulator. So I'd first measure the
resistance from board
ground to the emitter of Q702. It it's a short (or nearly
so), you'd want to
follow the -17V line to see what's holding it down. First
thing to look at
would be the 15uF capacitor (C709) running from the emitter
of Q702 to
ground.
F001, F002 and F003 are indeed spare fuses, so you can use
one of them to
replace F702.
Let us know what you find.
Greg
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Good deal Randy! Out of curiosity, what displayed error code did the blown
fuse cause?
Greg
----- Original Message -----
From: "Randy Scott" scottr9@yahoo.com
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Wednesday, August 26, 2009 6:46 PM
Subject: Re: [volt-nuts] 3458A AC board
Greg,
Thanks for the information. However, it was actually F701 (my bad) that was
blown. Taking a chance, I jumpered it to one of the spares and it seems to
be running great. It seems too easy... :)
Randy.
Error was "202 Hardware Failure - Slave Test: AC Board".
Randy.
--- On Wed, 8/26/09, Greg Burnett gbusg@comcast.net wrote:
From: Greg Burnett gbusg@comcast.net
Subject: Re: [volt-nuts] 3458A AC board
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Date: Wednesday, August 26, 2009, 7:58 PM
Good deal Randy! Out of curiosity,
what displayed error code did the blown
fuse cause?
Greg
----- Original Message -----
From: "Randy Scott" scottr9@yahoo.com
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Wednesday, August 26, 2009 6:46 PM
Subject: Re: [volt-nuts] 3458A AC board
Greg,
Thanks for the information. However, it was actually
F701 (my bad) that was
blown. Taking a chance, I jumpered it to one of the
spares and it seems to
be running great. It seems too easy... :)
Randy.
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