Tek 4051 troubleshooting

Ian Finder ian.finder at gmail.com
Thu May 19 16:20:44 CDT 2016

Hi folks,

I picked up a rather nasty Tek 4051 and gave it a good cleaning.
It has an issue with the power supply. Before I dive in properly myself, I
thought I'd just ask:

Has anyone seen a behavior where-

1) With the main logic board attached, the power supply makes a loud buzz /
    the +12 rail reads approx. 9v and the 15v rail is 13.5 or so. All
lights turn on as the cpu is obviously not running.

2) With the main logic board detached from the power supply (no load at all
on those rails?) I get a healthier 14.8 on the 15v rail and approx. 12 on
12. No hum / buzz.

I believe the supply is linear.

I suspect bad caps and a bad diode, but wanted to check here.

also in testing 2), one of the weird resistor network film packages on the
deflection board got really hot and made a smell. I hope it still works-
will certainly not be testing with the main board unplugged again.

Flood gun seems to be working.

- Ian

   Ian Finder
   (206) 395-MIPS
   ian.finder at gmail.com

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