Re: 454A -- overloading 150V rail, burned resistors on Z-board


Your voltages around Q1343 suggest that something here is amiss..... you do have +150V ok?
- is the +75V ok on VR1356?
- check that R1358 hasn't gone high.

NB Voltages through the chain Q1314 to Q1343 willl vary according to the setting of the trace brightness pot.

The mean DC voltage on Q1343 collector should stay up at +100V or so.
On my 454A, the voltage on TP1349 (= emitter Q1343) varies from about +5 at zero trace brightness to +20V for very very bright traces. This range may be affected by the grid bias setting in the CRT circuit.

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