This is my 2nd attempt at a post. Somehow I hit some combination of keys that undid about 15 minutes of typing before. So this will be without some background info.
Chassis p793, WGM 2775-OUT561H
Neckboard p719, WGM 2775-UOT561H
Frame has a sticker "replace with k7500 Chassis only"
Tube : Zenith A68AG01X
Many parts have been removed since the game, (Gauntlet Dark Legacy) got mothballed, but I bought new replacements for all of them.
Original problem was a vertical collapse I think, but the thing still ran. (HV, some picture or at least a line, etc.)
Should have been a quick fix, but no.
Doesn't come up. No pic, no HV.
Click click click....
Referred to flowcharts (RF Blue Book) and proceeded to go crazy testing the HOT for a short. Well of course it is continuous to ground, it's mounted on a grounded heat sink. Duh.
I eventually noticed some sort of insulator on another chassis I have for comparisons. (Not exact same model, but many of the same parts.)
Um, not duh?
Ah, lets try it with a piece of duct tape behind it. Hey it's running!
That lasted 15 or 30 minutes. Sigh.
Pretty sure my new HOT is shorted now. Base and Emitter are continuous.... No, it has to be bad now.
Why did it go? Heat? Or something else in the circuit shorted or otherwise straining things?
I pulled the HOT off of another donor chassis, hoping the HOT wasn't he reason that I pulled that particular board.
Now I can't get past the shutdown clicking.
Where it stands now:
I removed the HOT, and did a lightbulb test between the diode leg on that heatsink (looks like a transistor, but has 2 legs and is marked D) and ground.
Light comes on. TP202 shows 120V.
The last HOT I have been trying, well I'm not sure about it so I ran some diode checks on it. Maybe it's bad too? (I don't have another new one to compare to.)
(Red Lead) - (Black Lead)
Base - Collector .052, B-E .045, C-E .003 (beep), C-B .053
(Black Lead) - (Red Lead)(
Base - Collector .053, B-E .050, C-E .003 (beep), C-B .053
I have spent so much time looking for shorts its driving me crazy, but there might not have been one in the first place? And I likely made a mistake (or six) and made things worse.
I would appreciate any help to get this thing figured out.
Thanks,
-eric