Re: PSU Problems HP 8591A
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I have two 8590B SAs and both had the same PSU fault.? The Power LEDs were illuminated and the voltages (as read by a DMM) were OK, but perhaps a bit on the low end of the tolerance band.? When examined with a 'scope, all had 100Hz ripple (I am in the UK).? This suggested the main PSU reservoir capacitors were faulty, and yes, in each SA one of the pair was open circuit. ? I don't know if the PSU in an 8591A is the same, but it's worth checking.? IIRC, the faulty capacitor in each SA had a 'domed' top. ? Replacing the pair in each SA cured the fault in both. ? Good luck! ? 73, Mike, Mike Stevens, G8CUL/M0CUL/F4VRB. ?
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From: [email protected] On Behalf Of Kuba Ober
Sent: 01 October 2020 13:15
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] PSU Problems HP 8591A? That may help a bit but in most cases switchers either work or they don¡¯t. When they don¡¯t, usually the whole thing equally doesn¡¯t work since the outermost control loop has been broken. So nothing inside will have any signatures that would help much. So I think it¡¯s just lore. These supplies don¡¯t have large digits sections with signatures to begin with. Signature analyzers of that era worked on TTL inputs. They could help if you were fixing an Alto supply maybe, but for HP instruments - I highly doubt that. ?Nice description. You obviously you how these beasts work. ?For the novice, switchers are really hard to repair due to several control loops that are involved. ?Years ago, I read some techs were using HP signature analyzers to quickly diagnose switchers by using known signature points from a working model of the supply being repaired. ?Not sure if that method really works.
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Regards, Bernie Murphy
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