HP 3312A function generator maintenance

[dimkasta]

A few years back I bought a used HP3312A

I use it mostly on audio frequencies and have no serious problems with it.

However, the setting knobs are a bit jumpy, so I thought I should do some maintenance work on it.

I have located the service manual
http://literature.cdn.keysight.com/litweb/pdf/03312-90004.pdf?id=734381

I was thinking to try and clean the pots and check any electrolytic caps for aging problems.
Any advice on how I should approach this? Any other things I should check for?

Thanks in advance

[wn1fju]

Sounds like you are on the right track.  Always consider mechanical issues before electrical.  That is, a careful cleaning/lubrication of all the pots and pushbutton
switches often cures all ills.  I wouldn't think faulty electrolytics would cause your issues as they are probably mostly used in the power supply and faulty ones
would either render the unit completely dysfunctional or cause some massive distortion on your output.  Start with alcohol or a mild cleaner like the Caig Deoxit
products.  Don't expect the unit to work right away after cleaning - it usually takes an hour or two for all the cleaning fluid to dry up.

[dimkasta]

You got to love engineering that looks nice, tidy and squeeky clean 30 years later

[banzas]

Hi,
I have been experience some offset problems, any thoughts?

[wn1fju]

You would probably get more people to respond to you if you described the specific problem.  Just saying "offset problem" doesn't tell us anything. 

However, 1) check the positive and negative power supplies, 2) check the offset control potentiometer, 3) check for any loose or disconnected wiring, 4) check the op-amp that the offset control uses to inject the offset voltage, and 5) check the output transistors.

You will need to download a service manual of course.

[Chris56000]

Hi!

[You will need to download a service manual of course.]

Have you seen the one that is available?
It's so bloody furry and appallingly badly scanned that it's impossible to read anything on the circuit diagrams!

It's so bad that I'm going to use a page of this as an example of a badly copied manual in the last chapters of my T & M Theory and Repair Book!

Chris Williams

[wn1fju]

To Chris56000:

Yes, the free service manual download leaves much to be desired.

I got mine from Artek Manuals ($7.50US for electronic download).  It is perfectly fine. 

However, be warned that at some date, HP redesigned the A2 board on the 3312A.  Apparently, a schematic of the newer board may be unobtainable.  There were some forum posts about this a while ago and I don't remember the final outcome.