Trouble with an HY-5500 CRT -- HV supply not working

[user1]

I just made a discovery -- when the base and collector of the HOT are shorted momentarily, the TV will display various forms of the usual scan pattern, and sometimes even a mix between the scan pattern and static. When the TV is not displaying, the base is at +12V, The collector is open (connected through a capacitor, specifically) and the emitter is at +12V. I think this means that the PSU for the transistor is bad, correct?

[Alex KL-1]

Originally Posted by user1

I just made a discovery -- when the base and collector of the HOT are shorted momentarily, the TV will display various forms of the usual scan pattern, and sometimes even a mix between the scan pattern and static. When the TV is not displaying, the base is at +12V, The collector is open (connected through a capacitor, specifically) and the emitter is at +12V. I think this means that the PSU for the transistor is bad, correct?

About the terms, for not confusing... The "HOT" you cite here, is the one with heatsink? Normally the one we call "HOT" is the horizontal output, and this is the directly connected to flayback, and will not show the behaviour you described (then will be the regulator transistor). And in most little TV's the HOT don't have heatsink.

It seems to really have some PSU regulator bad behaviour. Also, Indeed, the main transistor regulator can be open (the transistor you shorted the B-E), or some near it. You can remove the transistors for testing with DMM in the diode scale, to be absolutely sure.

Is good to find the schematic for the TV, or, in the absence of, you can dowload every IC datasheet to study them and plan some tests (to be sure none contribute to the regulator or control it).