HP3325A Function Generator

[Malcolm Raven]

I have a HP3325A Function Generator in which the HP-IB (IEEE 488-1975) has recently stopped working properly. It no longer recognizes data characters received and issues Error 8. The Basic GPIB card and programme used have been working satisfactorily for several years and work OK with other instruments. The HP3325A works normally except for the HP-IB.   Any ideas most welcome.

Malcolm

[KJDS]

I would start looking at the obvious, is the connector ok, any cracked solder joints. Is the 5V rail in the vicinity as it should be?

[c4757p]

When you debug it, don't miss the optocouplers! Mine failed and took out the GPIB - not usually something you might normally suspect.

[Malcolm Raven]

Thanks very much for the quick replies.  I will try these immediately.

[SoundTech-LG]

The one I'm working on had a -hitload of problems. This is a very early 85th unit production, so A, and Rev B boards. Someone else had been working on this. They replaced the big 8000uF cap on the PS board but did not take the board out. Bad solder intermittent connection. The Fractional N 28 pin IC was overheating!!! Bummer! Unobtainium!
BUT!!!  checking the +15 revealed weak 15V with 500mV of 60 Hz ripple on it, BUT !!!  INTERMITTENT! So I ASSumed the IC was bad, because disconnecting the +15 line removed the ripple, and load. WRONG!!! Turned out to be an intermittent +15 regulator on the chassis heatsink. Replaced it, and BAM! no overheating, no ripple.
Found broken transistor leads on two TO-92's MPSH10, and MPSH81 comp pairs on the output amp. Bam! got rid of the bootup A-CAL Failure. No keyboard keys seem to work. Noticed key strobe signals without pushing any keys. Stuck key failures! Removed three, and there is still one more to go. Did get it to boot, self test, works fine, and passes all tests. Whew!
Just need some new key switches. was it worth it? Not sure. But I sure did learn alot! Quite entertaining.