Question on 7k series plug-in cleaning re: Tek wash method

Randy Newman

Hello Hakan:

I did see the note about old F/W. I am afraid my codes are not false, as I ran a quick check using the calibrator connected to both channels. Ch1, and Ch2 indicate different values. Ch1 seems accurate above 50 mV. Ch2 does not seem to be accurate anywhere.

I will go back and read your previous posts.

I have yet to read through the appropriate portions of the maintenance manual.
I’ll post more results once I have time to make measurements.




On Fri, Sep 17, 2021 at 10:23 AM, Randy Newman wrote:

.but sadly self-test fails with attenuators codes
7D20 with F/W below 1.03 are known to sometimes generate false error codes.
See my posts from last year:


Randy Newman

Hi all. Just purchased a 7d20, and powered it up in my 7854.
It was sold as working, which it mostly does…..but sadly self-test fails with attenuators codes. I looked here for previous posts and noted several mentioning cleaning contacts. And (maybe) PWB pads.

My questions:
1) has anyone tried the “wash in (Kelite) method per Tek publications on plugins, as opposed to full scope chassis? I remember reading wizard Analog designer Bob Pease mentioning washing PWBs in a dishwasher.

2) Has anyone tried cleaners such as DeOxit on relay contacts, and similar contacting surfaces?

I’d like to be able to clear the self-test errors with a minimum of disassembly, as my “workspace” is a makeshift temporary one, so projects must be very short term. Someday,I’ll work out a real test bench.

One note which might help with relay contacts: I remember reading about a non-abrasive method of cleaning fragile contacting surface using a strip of typing paper wetted with IPA. As I dampened paper was inserted between the open contacts, then they were closed, and the paper pulled through for cleaning.
If I remember correctly, it was for some relays in HP gear…..maybe attenuators relays in a 3325 function generator (I actually happen to have one with bad attenuators relays, but have not diagnosed the root cause).

I’d appreciate any wisdom on cleaning methods, esp w/r/t 7d20’s.