Newbie's First Questions RCA TS 721 Restoration

[Chris K]

Originally Posted by Yamamaya42

this is the tube voltage chart from the SAMs for the RCA 630ts which is very close.

http://suzaku.live-evil.org/sound-volt.jpg

Ref V14 15 16

it's normal to see almost no voltage aside from heater on the 6AL5

the 6AT6 also seems OK, pin 7 may be lower than what is said, but mot likely not an issue.

what is WEIRD here is the 6K6GT,,
You should be only be seeing negative voltage on pin 5, if pins 3 & 4 are negative then something is VERY wrong, especially if you have a good strong +225 bias on the far side of that 1k power resistor feeding it.

There's a wiring issue with one of the electrolytic caps...C131. I've got -75V DC all over the place here. Let me recheck what I did.

[Yamamaya42]

then you should have a dead set :O

gonna have to trace the main bias path from the 5U4 heater through the filter -> horz center pot -> vert center pot -> focus coil - > bleeder network to try to see where it's getting lost, and hope that it's not a unreplaceable part like an open focus coil.

[Chris K]

Originally Posted by Yamamaya42

then you should have a dead set :O

gonna have to trace the main bias path from the 5U4 heater through the filter -> horz center pot -> vert center pot -> focus coil - > bleeder network to try to see where it's getting lost, and hope that it's not a unreplaceable part like an open focus coil.

Yes, I did the 225V DC trace from the 5U4 to C131 and out many times over when I replaced all the electrolytic caps. I currently have a mix of the correct DC voltages and this odd negative voltage. Fortunately, the Riders comes with a wiring diagram which has come in handy many times during the initial stages of this project.

I don't think the focus coil is open because moving it does what it's supposed to do on the CRT but, as I've displayed here several times in this thread, what the hell do I know

So my plan is to meticulously retrace the 5U4 DC output checking voltages along the line until I find my screw up. My wife and I are leaving for a well deserved vacation tomorrow so, unless I act on an insane instinct to bring the TV and all of my equipment to Cape Cod, I probably won't have anything to post on this project for the next 8 or 9 days. I appreciate all of the help the forum members have offered to this point and I hope everyone who have been so generous so far will stand by until I pick this up again in a week or so. At least now I know, thanks to you, it's a major and possibly single issue of a miswiring or something easily corrected. I hope!