Re: Tek 576 possible power supply failure


 

Hi all,

I fixed this one... a faulty transistor.

I noted all voltages in the -100V and +12,5V supply, as they seem to depend on each other. With a little try-and-error (easy, as transistors are all socketed) I found the culprit.

I put the schematic of those 2 supplies together with the voltages (hopefully readable) in failure mode in the files section. See if anyone finds the faulty transistor from that information alone...

https://groups.io/g/TekScopes/files/2021.01.31%20-%20Tek%20576%20power%20supply%20failure%20mode.pdf

Later on I checked the small capacitors on the regulator board, they are all fine. When the unit is running I merely get some millivolts of ripple on any of the supplies, so I guess theres not much that can be improved.

Next its the step generator that needs some attention. Some steps are missing or skipped, looks like a problem in the counter / converter area. When that is done there are at least 2 bulbs in the readout that must be replaced. And the "invert" switch array cleaned, maybe.

cheers
Martin

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