My Attempt at Predicta Restoration

[PredictaNoob]

Originally Posted by DaveWM

half meg? geez there must have been a super critical adj. check check the tube resisitance on pin 9 of the 6dr7 vert out tube to ground. Should be around 450 ohms, give the meter a chance to settle in as there is a bypass cap across it. It must be set to nearly fully closed (min resistance).

It settled in to a steady 940 ohms. And when you say "It must be set to nearly fully closed" You are talking about the Vert Lin pot? If so, it made no difference to the reading, no matter where I set the pot.

[PredictaNoob]

Originally Posted by DaveWM

C3 that bypasses it will most likely be open, it sets next to the Pwr tranny and gets baked, dries out, at least that was the case on two predictas I worked on.

I'm not sure I understand you. I see C3 as a ceramic cap up on the video IF board. The only cap I see near the P.T. is C41, a .047 line bypass?

[DaveWM]

Originally Posted by PredictaNoob

It settled in to a steady 940 ohms. And when you say "It must be set to nearly fully closed" You are talking about the Vert Lin pot? If so, it made no difference to the reading, no matter where I set the pot.

interesting, that pin is supposed to be connected to the pot, so I assumed it should have done something. See if you can trace the pot to a tube pin.

[DaveWM]

Originally Posted by PredictaNoob

I'm not sure I understand you. I see C3 as a ceramic cap up on the video IF board. The only cap I see near the P.T. is C41, a .047 line bypass?

I am looking at the SAMs, C3 section A is one of the electros that bypasses the cathode of the 6DR7. The sams and the notes printed on the PC board do not match up. See if you can find a wire from the thin can (low volt 100mfd) going to the pin 9 of the 6DR7 (or to the pot that connects to that pin).

[PredictaNoob]

Originally Posted by DaveWM

I am looking at the SAMs, C3 section A is one of the electros that bypasses the cathode of the 6DR7. The sams and the notes printed on the PC board do not match up. See if you can find a wire from the thin can (low volt 100mfd) going to the pin 9 of the 6DR7 (or to the pot that connects to that pin).

AH, OK got it. Its labeled as E1 section 3 (100 mfd at 50v) and yes it is right up against the P.T., and yes it is open! (and so are the other two sections). I already have all electrolytic and cap replacements on-hand. I'm not going to re-stuff this can, but mount the new e-caps on the board. Heck the wire that connects that cap to the vert lin post runs a full 3/4 length around the board!

[PredictaNoob]

Originally Posted by DaveWM

interesting, that pin is supposed to be connected to the pot, so I assumed it should have done something. See if you can trace the pot to a tube pin.

I don't know what this pot is for now.
I traced the pot to a wire connected a lead for the 400v B+ that jumps over to the that same e-can, hooked to the 10 mfd 450v?

[DaveWM]

hmmm, maybe some kind of rigged up focus control. need more can you tell where each lead goes and I will see if I can find out whats going on. the Lin pot is a cathode bias pot, pin 9 to ground.

[batterymaker]

Originally Posted by PredictaNoob

I'm trying to replicate the control labels on the back of the cabinet top. It dawned on me that someone here might know the font that Philco used on these sets? Here's what I've got, so far. It isn't exact, but I'm rapidly losing concern about it...


This is Haettenschweiler 24 font size with a 4 point character spacing.

Another close-fitting font is Alternate Gothic No. 2.

[DaveWM]

ok duh, its the height pot, schematic say 3 meg pot. Still dont get the big resistor, it should be connected to a 1.5 meg resistor that goes to the plate of the 6DR7

[DaveWM]

check the resistance of pin 6 to the 275v source should be around 3.9 meg

[DaveWM]

what is the value of that big sand resistor tacked on?

[PredictaNoob]

Originally Posted by DaveWM

hmmm, maybe some kind of rigged up focus control. need more can you tell where each lead goes and I will see if I can find out whats going on. the Lin pot is a cathode bias pot, pin 9 to ground.

OK, I traced the two leads coming from the pot. Black goes to ground, red to the post marked "B+ 400 2" the orange and white wire jumps it to another post, then to the electrolytic as described previously. The circuit board path, I outlined with the red line, takes it to pin 9 on the audio out tube, 6BQ5.
Huh?
Tone control, maybe? I thought this might be an audio pot, at least it is similar to tone control pots I've seen in old tube amps.
I really don't know.
Let me know if this picture helps, or if you need me to take some other detailed shots.

[PredictaNoob]

Originally Posted by batterymaker

Another close-fitting font is Alternate Gothic No. 2.

I don't have selection in Power Point. Could you send me an example?

[PredictaNoob]

Originally Posted by DaveWM

what is the value of that big sand resistor tacked on?

Even though it is two 2K resistors connected in parallel, the resistance only measures at 939 ohms.

[PredictaNoob]

Originally Posted by DaveWM

check the resistance of pin 6 to the 275v source should be around 3.9 meg

If you mean the 275 from the VOT, I can't get a good reading. It starts around 18M and climbs beyond what my VOM can handle. Or should I be checking from another location?