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8643A failure

 

My 8643 failure message indicated 5V supply failure. Voltage at test point measured 4.9 volts. I replaced all the capacitors in both switching supplies of the 8643A. Both supplies checked out OK before capacitor changes, and OK after capacitor changes. But I'm happy it has new capacitors.

The battery voltage was OK, but being old and not interested in leaks, it has a new set of 3xAAA in little plastic holder.

After reading about tinned Molex connectors developing voltage drops I sprayed DeOxit on pins of the power supply connector, and both input and output connectors of the power filter board. And of course the cable pins that plugged into those connectors. Power supply and filter board input connectors were tinned pins. Pins on the output end of the filter board were gold. Did the best I could, but it wasn't as good a job as I would like to have done.

NONE of the connector bodies were discolored. There was maybe 1/4 volt drop, and not that many hours of use, before I took it apart. Probably not enough time and heat to discolor the Nylon.

Applied power, and test point now measures 5.10 volts. So looks like it was voltage drop in the tinned Molex connectors.? No error message. While I haven't checked exhaustively to verify everything is working, but I expect it's OK again.

THANK YOU GUYS FOR POINTING TO THE CONNECTORS

Regards - Bill W7AAZ
 

开云体育

Thanks for posting a follow-up. Glad your 8643A is working.

Tony
AD0VC

From: [email protected] <[email protected]> on behalf of Bill Carver <bill@...>
Sent: Sunday, March 16, 2025 6:26 PM
To: [email protected] <[email protected]>
Subject: Re: [HP-Agilent-Keysight-equipment] 8643A failure
?
My 8643 failure message indicated 5V supply failure. Voltage at test
point measured 4.9 volts. I replaced all the capacitors in both
switching supplies of the 8643A. Both supplies checked out OK before
capacitor changes, and OK after capacitor changes. But I'm happy it has
new capacitors.

The battery voltage was OK, but being old and not interested in leaks,
it has a new set of 3xAAA in little plastic holder.

After reading about tinned Molex connectors developing voltage drops I
sprayed DeOxit on pins of the power supply connector, and both input and
output connectors of the power filter board. And of course the cable
pins that plugged into those connectors. Power supply and filter board
input connectors were tinned pins. Pins on the output end of the filter
board were gold. Did the best I could, but it wasn't as good a job as I
would like to have done.

NONE of the connector bodies were discolored. There was maybe 1/4 volt
drop, and not that many hours of use, before I took it apart. Probably
not enough time and heat to discolor the Nylon.

Applied power, and test point now measures 5.10 volts. So looks like it
was voltage drop in the tinned Molex connectors.? No error message.
While I haven't checked exhaustively to verify everything is working,
but I expect it's OK again.

THANK YOU GUYS FOR POINTING TO THE CONNECTORS

Regards - Bill W7AAZ
 

开云体育

Dear Bill,

Many thanks for the update.?

My 8643A has displayed this fault code from time to time.

I will check the connectors carefully when I take it out of the rack for oven power supply repair.

Using tinned connectors was very poor form for HP, but of course the detail was not very visible.

By contrast, as a young engineer working on things for the US Gov’t, I was surprised to see that our heatsink blocks were gold plated on all surfaces. There was no electrical or thermal reason for this, so I naively asked my superiors why we spent so much money doing this. This resulted in pitying looks, smiles and the explanation- “When the sponsor visits it helps him to see that he is getting value for money on the contract.” Another lesson learned.

Regards,

Alwyn
_____________________________________________________

Alwyn Seeds, Director
SynOptika Ltd.,
114 Beaufort Street,
London,
SW3 6BU,
England.


SynOptika Ltd., Registered in England and Wales: No. 04606737
Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom.
_____________________________________________________
 

This is a common failure point on these.? Simply removing and reinstalling the connector to the backplane board on mine returned it to specified voltage.? I then cleaned it with denatured alcohol and a toothbrush.? Glad it fixed yours!

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