HP 33120A problems - Page 1
Forum section: electronics / repair

author: vaualbus
author_rank: Frequent Contributor
timestamp: August 16, 2014, 12:07:31 am
content: 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.

author: free_electron
author_rank: Super Contributor
timestamp: August 16, 2014, 10:59:37 am
content: 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.

author: vaualbus
author_rank: Frequent Contributor
timestamp: August 16, 2014, 12:42:42 pm
content: 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?

author: vaualbus
author_rank: Frequent Contributor
timestamp: August 16, 2014, 01:30:25 pm
content: 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.

author: pinkman
author_rank: Regular Contributor
timestamp: August 21, 2014, 12:32:01 am
content: 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.

author: vaualbus
author_rank: Frequent Contributor
timestamp: August 24, 2014, 03:00:34 pm
content: Thany you but unfortunally the item has been sell on ebay. See I'm so unlucky for this stupid display.By the way I'm from Turin

author: pinkman
author_rank: Regular Contributor
timestamp: August 25, 2014, 05:45:58 pm
content: Alberto,Let me know if you find another for sale in the US, I would be happy to bring it. I know how frustrating it can be when you can't find repair parts!