What's wrong with my 5151?

[Agent Orange]

I was getting an unusual voltage jump up to 16V at the collector that corresponded to the display becoming distorted after running for a short while. Nominally it should be at 15V since it parallels the 7815. At first I suspected the 7815 wasn't regulating properly and replaced it but that had no effect. Now it is solid

View attachment 66953

Presentation looks real good and that's a fine looking monitor.

 

[Chuck(G)]

believe it or not it was the MJ2955 all along

Was that a TO-220 epoxy job or the good old TO-3 can?

I've had TO-220 MJ3055 (the NPN cousin) go bad by being cooked, but never in the TO-3 can.

 

[maxtherabbit]

Twas the can

 

[Chuck(G)]

That's a bit surprising--2n3055 TO-3s are generally pretty rugged; the 2955 should follow the pattern.