Re: Tek 2235 power supply

Hi Jim, did you manage to get the download? Here is my latest findings. I'm
not over volting. When I measured on the correct ground point, test point 950,
test poin 940 never quite reaches 40 volts. This would tell me that there is
an over current problem however I have lifted all the jumpers (+/-8.6, +5,
+30, +100) and I removed the voltage multiplier completely from the board and
there is no change. So is the over current on the primary side then? I went
ahead and removed the GP caps and put in hi quality Nichicon low ESR's in
their place. I have a good sawtooth wave at pin 5 of U930, oscillation is
visible through Q908 and the FET. The SCR doesn't have anything on the gate.
I can see the voltage drop at R926 (it measures 150k) when it 'chirps'. There
is a short duration 5V pulse from the IC at pin 14 (the ref output) and I can
see a small increase in the voltage at pin 16 also timed with the chirp. R907
measures good (.2 ohm). On the other side of the transformer, each rail tries
to come up gaining about 3/4ths their normal values and then falling again.
My probe hit and killed Q930 and now I have to order a replacement for it. I
see 1 volt at pin 12, no chirping and Q930 is resistive now...

Any help is greatly appreciated. I will paypal you a beer! :-)

~RB

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