Electronics > Repair

HP 33120A problems

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vaualbus:
I'm still try to repair my HP33120 Arbitrary function generator but after changing the main dac I have three problems.
      - First I broke the vacum displa so I can't see nothing on the screen. Anybody know or have a display to sell to me?
        (I found a seeler on ebay that sell the display only in US, unfortuannlly I'm in Italy, fuc......).
       
      - The output amplifier is gone. Initially after replacing the main dac I saw I strange signal at the output, I did some check and found a burn    resisitor, change it with a new one but after turning on the device it burn with smoke and now, after replacing it again, I see no signal at the output.

      - The last problem is a little bit trick. When I power up the instrument I can change the frequency and I have a sine like the manual said.(I have the signal at the +AMP_IN and -AMP_IN on the board) but If I select for example a square wave I can't select back the sine wave. I heard the bip but I can't change the waveform. I have the same problem with the Freq button, so If I press the amp button I can't come back to the freq selection.
Of course If I had a display it would easier to know what is happening.
The two buttons are in the same column but If it was a column  problem, on the display board, why the instrument beep when I press a button? 

Wish someone can help me.
Best regards, Alberto.

free_electron:
Ouch ... That is going to be a tough cookie.
Replace all transistors in the endstage.

The glass. Buy from agilent or look for another donor, but you may be better off repairing the other donor.

vaualbus:
ya I will replacing all the output transitor.
But first I want to solve the buttons problems.
Any idea what can cause the buttons problem?

vaualbus:
And, of course, the entire front panel assembly is no more avaible from agilent/keysight.
The part number is 33120-66502 but it said obsolate.

pinkman:
Alberto,
Where are you in Italy?  I'm from the US and I'll be in Milan/Torin for a day, at the end of next month.  If you're near one of those cities, I could bring the display with me and meet you somewhere.  I won't have a car so meeting near milan or turin airport would be best.  I looked on eBay for the display but didn't find it, you would have to send me a link.  Let me know.

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