[time-nuts] 5062C power supply problem

corby d dawson cdelect at juno.com
Tue Aug 19 17:09:21 EDT 2008


You need to make sure the ion pump current has dropped to <10 on the
meter or else the +18V supply is disabled.

If it is high watch the 18 volt meter position and momentarily remove the
A7 high voltage by pulling out the HV connector.

If the +18 comes up then reconnect the HV and let the unit run a couple

Hopefully you should see the ion pump current slowly drop, when it falls
below the trip point the CS oven and +18V will come on and the ion pump
reading will rise again, possibly pegging.

This is normal for a unit that has been off for a long while. It can take
a couple days of cycling to finally drop and stay below the trip point.

If the +18 is indeed dead then you can hook an external +18V @ 1.5A
between chassis ground and one of the marked +18V runs.

Current draw is about 1.3A.

This is just for momentary testing as the ion pump interlock will be
bypassed. If you are patient you can apply the +18V, watch the ion pump
peg, remove the +18V, wait till the ion pump drops below 10, and repeat
until you can leave the +18V connected and the ion pump is 10 or below.

I have done this while working on these units and also have replaced the
+18V card with  a DC to DC module that has remote gate capability so that
the ion pump circuit will work with it.

Hope this helps,

Corby Dawson
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