Perfect Keith.
This clearly shows that Q1416 is always in saturation and that CR1416 never conducts (is even reverse biased).
Hence I think the fault is not in the regulator circuits.
You might measure the average collector current of Q1418 with an ammeter in series with the fuse. For a good Q1418 I expect some 0.2 - 0.3 A. Note that Tek's spec of current gain 20 is for large collector current, 3 A. The absolute and differential gain decrease dramatically when collector current increases. At small current a gain of 100-150 is well possible.
When the collector current is in the range I mentioned then I expect a fault further on. Though the Ft of Q1418 might have suffered for some reason and this transistor is the culprit. The 2N3055 may also have been replaced by a PO, who knows. It seems that not all 2N3055 makes/types work satisfactory in this application. But your HV did work before and failed suddenly.
Albert
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Thank you Albert. I put the scope in dc coupling and centered it. Needed to
adjust the scope to .5V/div in order to keep the same gain for comparison.
Here are the waveforms:
/g/TekScopes/photo/49286/9?p=Name,,,20,1,0,0
Collector is a hair more than emitter, base is a little more than twice the dc
bias, as you say about 0.65V.
Is that the correct way?
Keith
