TECH: Voltage Problems - 15V2000

Greetings all,

Once again, I am back to working on a 15V2000 out of a BZ Cabaret. It has a
voltage problem somewhere in the HV cage. The symptoms are that when cold,
all is well and voltages are near nominal on all pins of the P900 connector.

After about 20 minutes of warm-up, however, all the output voltage pins on
P900 drop significantly, along with the voltage at the tube anode (example:
12.5 KV to 9.2 KV). The voltage on pin 8 of P900 (voltage to the HV cage)
does not drop. The main symptom of all this is the monitor blooming (a
little more vertical than horizontal it seems).

Since all the other voltages coming from the HV cage seem to be derived from
the HV transformer, I am thinking (hoping) that a component is "thermally
challenged" between P900 pin 8 and the HV transformer causing all the
voltage to drop all over (anode, P900 pin 1, 2, 4 & 5). Oh, and the freeze
spray trick did not work this time on any of the components.

I have already completed a cap kit, so ruling out those caps, I looked at
resistor R900 (21 Ohm, 15 Watt) and noticed that the output was
significantly lower than the input (about 60% of the input). Is this normal?

I would like to hear suggestions on where to continue looking. I suppose
that the transformer itself could be bad, but would a bad HV xformer take up
to 20 minutes to reach a full voltage drop? I assumed that when a HV xformer
goes bad that it just goes out completely.

Thanks for any help!
-Commander Dave

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Received on Tue Nov 12 20:09:36 2002