Repair : HP 3245A precision DC/AC source

[Samogon]

OK, it has been fixed.

1. As i said Q901 was dead short, replaced both Q900 and Q901 (BUZ71A) as they make pair so to be sure that i have close parameters i used  IRFZ20PBF
2. Blown linear regulator U906 (LM7915) replaced with same
3. Charred C900 470uF 25V changed
4. And fuse which blown after all components listed above went kaboom. Well at least it prevented more catastrophic consequences.

So need to order to replace Puffner filter and calibrate this nice peace of equipment.
But 10V is too low i will be locking for unit with option #2 or amplifier board itself. If some one has a lead i would appreciate.

[Samogon]

About K3 relay, stupid me, it did stuck in wrong position, but what i have expected from latching relay  . Once power rails were restored, firmware run initialization sequence and it K3 into proper position. Well, now i have spare relay for $20

[rastro]

Has anyone found a replacement source/part for C900 on the source boards.  This is the 470uF/25V radial electrolytic with an additional ground lead (screen?) at the top?

[JesseLackey]

If you're going to dig in, why not do 3? 
(see attached pic... not sure it shows up inline in the post, I'm a newbie here)

Been scouring this thread and the excellent writeup at <https://xdevs.com/fix/hp3245a/>
Hopefully somebody out there is still interested in these beasts, I'd enjoy any commentary and help.  For sure I'll need to replace the NVRAMs.
I don't have an HP 3458A, but I do have a calibrated Advantest R6581T for DC V/I.  And USB->GPIB coming soon.
Cheers all!
J

[JesseLackey]

...and first questions, if anyone has some general tips...

1. the Schaffner is riveted (?) to the frame, at two points.  I don't need to rivet in the Delta 06geeg3e replacement (or maybe just a new Schaffner), but ... how should I remove it?  Is this a drill-out-the-rivet job?  I've never had to deal with this before.

2. opening up the 1st of the three, everything looks really pretty good, a little dust is all.  The only date codes I can find are on the EPROMs, 8849 and 8850, meaning the 49th and 50th week of 1988, one assumes.  Is there a date code anywhere else?  I wonder if the date code is not necessarily when the EPROM was programmed but the revision of the firmware.  Seems unlikely tho.  Thoughts?

3. The electrolytics all look just fine.  I'm going to spot check ESR on 2-3 largest ones, if the ESR looks ok, should I replace anyway?  Opinions?

From the date code, and somebody's post here about list price in 1988, the one I'm working on (it has option 1, two channel output) cost nearly $7000, which is nearly half the tuition for my sophomore year at Cornell!
Thanks all!
J

[Samogon]

I have drilled out rivets with drill bit bigger than rivet heads diameter. Punch pivoting hole in the center of the rivet head.
First if all make complete self test, get service manual and CLIP
So that is fir the start

[rastro]

3. The electrolytics all look just fine.  I'm going to spot check ESR on 2-3 largest ones, if the ESR looks ok, should I replace anyway?  Opinions?

Negative, C900 must (and here must is must of the utmost must) be replaced with a 35V replacement

The unit with the "ERR 92" most likely has the C900 bad on one of the driver PCB's. 

[JesseLackey]

Hi all, thanks for the tips, I'm going to replace C900 and all the other electrolytics besides.  I'm making the shopping list now.
I have all the docs for the 3245A, including the very useful CLIP.

I have a dumb newbie problem.  I can't pull the pcb shown below from the backplane, I've removed all 7 screws and it moves a few mm but then it seems like it is latched in place or something like that.
I've used a fair amount of force.  I want to make sure I'm not missing something before I pull harder.
Image below.
Any thoughts greatly appreciated.
J

[PartialDischarge]

There is a screw on the side that relases the metal plate over which both boards are mounted.
Also buy some green through hole fuses that that board has near the connector, cause they may be blown

[rastro]

The PCB's are a pain to remove - lot of jiggle and sliding.  There should be a procedure in the manuals as I recall.  Check for PDF's on line. 
I had the C900 go bad.  You definitely need to order the solder in fuses - most likely blown.

[PartialDischarge]

The PCB's are a pain to remove - lot of jiggle and sliding.  There should be a procedure in the manuals as I recall.  Check for PDF's on line. 

They are pretty easy actually, the trick is to remove the lateral screws that hold the metal plate. Then this metal plates shifts both upper and lower boards out of the connector

[JesseLackey]

So nice to have your help rastro and mastertech!  I was able to remove the boards, I'm not sure removing the metal plate was actually necessary but it allowed everything to be more jiggle-able and it was then easy.
I'm taking apart the working unit of the 3 so all fuses are fine (I continuity checked just to be sure), but that is a great tip, I'll get some for the other two units.

Any thoughts on the DS1235YW-150?  I'm going to need 6; octopart.com comes up with only 2 places with the full part number.
Is there a recommended (by eevblog people, not Maxim, where you can't even get the datasheet it looks like) replacement?

<https://www.maximintegrated.com/en/design/technical-documents/app-notes/2/202.html> has some good info I'm looking at.
also: <https://www.avsforum.com/forum/16-crt-projectors/246228-what-replace-dallas-ds1235yw-150-a.html>

I'm about to buy a power duster too, the "metrovac datavac" was recommended in a post on eevblog, but the "Compucleaner 2.0" is substantially cheaper and has good amazon reviews.  My air in a can is now just an empty can and I decided no more cans.

Tx all!
J

Update: from the maxim appnote referenced above:
"What's a DS1235?
A number of years ago, Dallas Semiconductor® had a 256kb NV SRAM product called the DS1235. It was functionally and physically identical to the DS1230, with the exception that the DS1235 had a five-year data-retention expectation instead of 10 years. An alternative is the DS1230 with the same power-supply tolerance, and with a performance rating equal to or faster than the original DS1235 product (for example, the DS1235Y-150 should be replaced by a DS1230Y-70+)."

So there we have it!
J

[JesseLackey]

Hi Alan, firstly thank you so much for all your info regarding the HP 3245A.  It gave me confidence to buy & work on rebuilding/repairing no less than 3 of them (simultaneously!)

I just today got GPIB going with a new NI USB<->GPIB converter, and your calibration app (V0.2) was able to see the HP 3245A.  A great first step.

I'm about to order a GPIB "splitter" so that I can talk to the HP 3245A and a HP 34401A simultaneously.  I don't have a HP 3478 but the 34401A can emulate it, apparently nearly completely.
(I do have an Avantest R6581T w/NIST cal, but it is DC V/I only, no AC).

2 questions for you ...
Is there a more recent version of your app?  The 0.2 was the latest on your site.
Are you willing to share source code?  Being able to tweak it could be very helpful; I have visual studio and long experience with C/C++ and a little with python.  I assume this is C.  Modifying it to use my R6581T for the DCV/DCI portion would be pretty fun... and having code like this is a great starting point for further GPIB adventures.

Many thanks in advance!
J

[Omicron]

Has anyone found a replacement source/part for C900 on the source boards.  This is the 470uF/25V radial electrolytic with an additional ground lead (screen?) at the top?

Did anyone find a good replacement for this cap? Is the 3rd lead just there as a mechanical support or is it indeed used for a screen?

[Samogon]

I just used regular radial capacitor, bent connector and glued to PCB with 704 silicon rubber glue.

[Omicron]

It seems the original capacitor is from this series from Vishay:

https://www.vishay.com/docs/42054/672d.pdf

According to this the third terminal is not connected (see page 2). It seems it has a rating of 2.35A ripple from 20KHz to 100KHz and an ESR of 0.22 to 0.08 ohms. So I wouldn't replace it with just any generic 470uF capacitor. I think I will be using this one:

https://www.digikey.be/en/products/detail/panasonic-electronic-components/EEU-FR1H561B/3072260

I'm taking a higher value because the original is specced at -10% to +100% and the replacement is +-20%.