EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: Disciple on January 25, 2021, 10:01:37 am
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Greetings Gentlemen,
I have an issue with my HP54504A. When I do the self calibration operation for channel 1 I get the error : Failed Gain Cal Chan 1 0000 0000 0010 0000. All other calibration test are passed with success. The calibration is passed with sucess for channel 2.
When I go to the service menu, I have for Chan 1 gain the 0020H error code.
I search a clue on the service manual but I found nothing. Do you have any idea where I can start to search ?
Thank a lot for your help,
Disciple
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The input attenuator may be damaged or just dirty. Try cleaning it or swap around to see if the problem moves. You DON'T want it to be a custom IC. There is some talk about the input attenuators, in particular the 50ohm switch. Swap them first, PITA I know.
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Set Chan 1 50 ohm input impedance to ON. then, measure the input resistance. If higher than 50 ohms, likely the relays are problematic, possibly a damaged or open 50 ohm resistor... Sometimes switching them from 1meg to 50 ohms repeatedly may temporarily clear a relay problem. Then try a reCal to see what happens.
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Set Chan 1 50 ohm input impedance to ON. then, measure the input resistance. If higher than 50 ohms, likely the relays are problematic, possibly a damaged or open 50 ohm resistor... Sometimes switching them from 1meg to 50 ohms repeatedly may temporarily clear a relay problem. Then try a reCal to see what happens.
That's good advice. And simple. The relays don't get switched much. A Tektronix tech told me they take the problem attenuators and "buzz" them for an hour to self clean the contacts.
However, they had a special setup for that.
On the HP scope... yep... try manually switching it if possible. Otherwise you have to pull the attenuators and manually clean them.
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Thank you all for your help. I was offline during few month due to a lot of work. I will try during my holiday to finish the repair.
Thank a lot again !