Author Topic: Bought a 3458A but...  (Read 614 times)

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Offline wolfy007

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Bought a 3458A but...
« on: March 27, 2020, 05:37:37 am »
Bought a second 3458a recently, claimed working. Talked to the seller and seemed genuine and helpful. He dropped it of to my sisters house, she lived near by, and I picked it up.

Problem is I got it home and it wouldnt power on. So recently I opened it up to take a look and repair it, mostly looks clean, checking A6 board for issues but then...

On the A5 board, under the GPIB port, I found spew from a ruptured IEC EMI filter. The filter had been replaced, but the ass that must have replaced it didnt clean up the mess and as it appears to be a rather stubborn mess to remove happened many years ago. The previous owner never opened it so wasnt aware of this but never had problems with it.

I have tried cleaning it with isopropyl but its barely coming off. Its coming off the frame (& its caused a bit of corrosion) but any ideas on a safe way to remove this spew-now-glue from the A5 board (picture below)?

PS: A5 board is revB  and A6 board is RevA (and has a couple bad caps), latest date code suggests manufactured after april 1994
« Last Edit: March 27, 2020, 06:27:33 am by wolfy007 »
Tek:222A,212,TAS465,TDS460A,2465,2465B,2467,TM504,TM506,SG504,SG503,PG506,TG501,SC504,PS503a,FG501a,DM504a,PG501,7603+7L12,7CT1N Datron:4707
BWD:835,539d,521,504,141,160a,170 Fluke:8060A,8024B,8025A,27/FM,87,87III,PM6685 HP:54602A,5315A,3478a,3468A,3457a Keithley:196,197,228a Solartron:7081,7151
 

Offline MiDi

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Re: Bought a 3458A but...
« Reply #1 on: March 27, 2020, 08:08:24 am »
What a mess and it is all over the place!
I would try to scrub carefully with sharp plastic e.g. spudger, plectrum or hard wood with sharp edge.
For cleaning the residues you could try a good pcb cleaner - in my experience they clean better than pure ipa.
Simple soap could be worth a try too.

If you do not already know, TiN has great articles on repairing on xDevs.com and here too.
For recapping my 3458A Worklog with a detailed overview of the parts that were replaced may be useful.
 

Offline vonB

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Re: Bought a 3458A but...
« Reply #2 on: March 27, 2020, 08:15:59 am »
I was using couple of times somethink like "fireplace window cleaner" with good results
 
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Online Kleinstein

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Re: Bought a 3458A but...
« Reply #3 on: March 27, 2020, 08:35:21 am »
The good thing is that this is only the digital / input power supply. So this part of the circuit is not sensitive to leakage. If at all it would be SRAMs that may need a little more current, but these are already a little away from the real mess.
 

Offline MadTux

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Re: Bought a 3458A but...
« Reply #4 on: March 27, 2020, 11:10:52 am »
That's only stinking tar puked out of the Schaffner-Paffner filter.
Soak it in hexane or some other nonpolar solvent.
Gasoline for 2 stroke chainsaws without benzene and other stinky aromatic hydrocarbons should work great, too.
 

Offline wolfy007

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  • Back into electronics again, as a hobby this time.
Re: Bought a 3458A but...
« Reply #5 on: March 28, 2020, 03:07:23 am »
Thanks everyone, will give it a go. Normaly I repair scopes, signal generators, power supplies even the odd voltage reference and such, but this is more sensitive, more intricate and expensive so taking my time and hopefully learn something new in the process. May ask a few more questions before this one is done.
« Last Edit: March 28, 2020, 11:02:23 am by wolfy007 »
Tek:222A,212,TAS465,TDS460A,2465,2465B,2467,TM504,TM506,SG504,SG503,PG506,TG501,SC504,PS503a,FG501a,DM504a,PG501,7603+7L12,7CT1N Datron:4707
BWD:835,539d,521,504,141,160a,170 Fluke:8060A,8024B,8025A,27/FM,87,87III,PM6685 HP:54602A,5315A,3478a,3468A,3457a Keithley:196,197,228a Solartron:7081,7151
 


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