I finally got one!!! Philco Predicta - Page 3 - Videokarma.org TV - Video

decojoe67 · #31 10-06-2019, 06:26 AM

Quote:

Originally Posted by static1701

I ordered all the replacement caps today. I had to get the Factory service manual because the numbers on the board did not match the numbers in the Sams parts list. I am debating removing the board from the chassis or just clip and solder. I don't really care about keeping it original... I just want it to work correctly.

A friend of mine has done vintage TV repairs since the '60's, and a countless number of Predicta's. He laughs at the hassle most people make out of repairing them. The as-found Debutante I have, he repaired while I waited without removing anything. The sets been working fine for me 10 years later. It's nice doing an intense restoration of any old chassis, but it isn't necessary - and sometimes will cause more problems.

static1701 · #32 10-06-2019, 06:43 PM

Quote:

Originally Posted by decojoe67

A friend of mine has done vintage TV repairs since the '60's, and a countless number of Predicta's. He laughs at the hassle most people make out of repairing them. The as-found Debutante I have, he repaired while I waited without removing anything. The sets been working fine for me 10 years later. It's nice doing an intense restoration of any old chassis, but it isn't necessary - and sometimes will cause more problems.

I am torn as far as how I want to do it, one day I feel like I should pull the board and replace everything and the next day I think I will just clip and solder just what needs replacement. I have been looking at connectors online and thinking about adding a connection to all the wires to make it easier for next time. I just don't know. The new networks arrived the other day and I am just waiting on the rest of the caps to arrive before I get started.

Electronic M · #33 10-06-2019, 10:00 PM

Quote:

Originally Posted by static1701

I ordered all the replacement caps today. I had to get the Factory service manual because the numbers on the board did not match the numbers in the Sams parts list. I am debating removing the board from the chassis or just clip and solder. I don't really care about keeping it original... I just want it to work correctly.

If it is a 10L43 (or similar) with holes under the PCB like mine you can split the difference... leave all the wires connected, remove all the hold-down screws on the board, unscrew the vertical transformer, and lift the fingers that hold down the wire harness to the chassis...Then you can lift the board enough to get to all the pads underneath through the holes with a thin iron (or at least not obtusely large Iron)....you can leave all the wires connected and change any/every part on the board this way, and it is a heck of a lot less invasive and less work than removing/unwiring the whole board from the set and reinstalling it wire by wire.

static1701 · #34 10-07-2019, 06:02 AM

Quote:

Originally Posted by Electronic M

If it is a 10L43 (or similar) with holes under the PCB like mine you can split the difference... leave all the wires connected, remove all the hold-down screws on the board, unscrew the vertical transformer, and lift the fingers that hold down the wire harness to the chassis...Then you can lift the board enough to get to all the pads underneath through the holes with a thin iron (or at least not obtusely large Iron)....you can leave all the wires connected and change any/every part on the board this way, and it is a heck of a lot less invasive and less work than removing/unwiring the whole board from the set and reinstalling it wire by wire.

It is a 10L43, I will give this a try first.

Thanks

static1701 · #35 10-07-2019, 07:43 PM

The caps came in today, hopefully I will get some time this week to get started on it.

cj_reha · #36 10-07-2019, 08:47 PM

Quote:

Originally Posted by static1701

The caps came in today, hopefully I will get some time this week to get started on it.

Wishing you good luck! I'm still fighting with mine, trying to figure out why there's no high voltage after a recap and re-assembly...

Electronic M · #37 10-07-2019, 09:06 PM

Quote:

Originally Posted by cj_reha

Wishing you good luck! I'm still fighting with mine, trying to figure out why there's no high voltage after a recap and re-assembly...

Look up the schematic here:http://earlytelevision.org/tv_schema...ms_philco.html measure the 1st and 2nd grid voltages on the H output tube and report back. Which one deviates and which way it deviates will tell what portion is bad.

cj_reha · #38 10-07-2019, 10:03 PM

Quote:

Originally Posted by Electronic M

Look up the schematic here:http://earlytelevision.org/tv_schema...ms_philco.html measure the 1st and 2nd grid voltages on the H output tube and report back. Which one deviates and which way it deviates will tell what portion is bad.

Alrighty, pulled the horizontal tube:

- On grid 1 (expected -45V) I get nada.
- On grid 2 (expected 200V) I get around 310 volts.

I've read Phil Nelson's excellent article on restoring his Debutante, and even though he had the same problem I do, I've already replaced the couplets with reproductions from TV Restorer Guy's website. I feel like I'm missing something here.

Electronic M · #39 10-07-2019, 11:11 PM

Your problem is in the horizontal oscillator. I assume you have changed all tubular paper dielectric caps, lytics and the couplates. Check resistors, and tube sockets (metal contacts break internally and go open), osc coil, solder joints, and B+ to the stage.

cj_reha · #40 10-08-2019, 07:11 AM

Quote:

Originally Posted by Electronic M

Your problem is in the horizontal oscillator. I assume you have changed all tubular paper dielectric caps, lytics and the couplates. Check resistors, and tube sockets (metal contacts break internally and go open), osc coil, solder joints, and B+ to the stage.

All caps, resistors, tube sockets, and couplates have been changed. I haven't checked the coil, but I don't think that would be the problem as the set did have high voltage before I took the board out to recap/change couplates/etc. I think I'll make my own thread about troubleshooting as I'd rather not derail this one.

Electronic M · #41 10-08-2019, 08:48 AM

Quote:

Originally Posted by cj_reha

All caps, resistors, tube sockets, and couplates have been changed. I haven't checked the coil, but I don't think that would be the problem as the set did have high voltage before I took the board out to recap/change couplates/etc. I think I'll make my own thread about troubleshooting as I'd rather not derail this one.

Good plan.
One thing I noticed on second read is that you measured the voltage on the output with the tube pulled...you want to remeasure with the tube installed....G1 only goes negative DC through grid-cathode rectification of the drive signal...pull the tube and you won't read negative there no matter what you do.... also the amount of G2 voltage will change depending on the fault...(assuming good G1 drive) high G2 means something in the flyback or later is shorted, low G2 means the damper or something else in the path from the damper B+ input to the h output plate is open (or in one of my sets it meant the width pot was open).

judge · #42 10-08-2019, 10:31 AM

Quote:

Originally Posted by cj_reha

All caps, resistors, tube sockets, and couplates have been changed. I haven't checked the coil, but I don't think that would be the problem as the set did have high voltage before I took the board out to recap/change couplates/etc. I think I'll make my own thread about troubleshooting as I'd rather not derail this one.

I had the exact same problem. The cause was a bad replacement couplate. Do you still have the original you can try?

static1701 · #43 10-08-2019, 06:05 PM

So today I replaced all the caps and networks. When I applied power to the set, at first it did exactly what it did before (Fill the top half of the screen) The line at the middle and the over all picture was much brighter. Within a short time, the picture went to just a line in the middle. The v.lin pot started to smoke so I shut it down. Adjusted the pot and tried again and it did not smoke but it did not work either. I am perplexed. I did a quick check and did not see anything wrong but I am going to go over everything again. I did not remove the board, just clipped and soldered (Wanted to avoid this problem of it not working after a re-cap) Help.....

static1701 · #44 10-08-2019, 06:24 PM

I just tested the 6DR7 and one section is shorted. It was not like that when I tested it when I first got the set. So I don't know if something old took it out or if something new took it out but now I have to check my collection for another one to find out.

static1701 · #45 10-08-2019, 06:41 PM

Replaced the tube, tested. Just a line. Shut it down and tested the new tube and it is still good with no shorts.

I think I may have figured it out, the cap at C14, I think I have the wrong one. The value is correct but it looks like the square AC cap, not like the rest of the poly caps that I ordered.

I cut out C14 and put the original back. The V.lin pot was done, I replaced it with a sub (Not the right value but I wanted to see if it mad any difference. That restored the set to the way it was before. I noticed that the 6DR7 was red plating, so I shut it down. (I think that happened because the original C14 is bad) I ordered a replacement cap, and I will order a new pot for the one that failed.

On a good note, since I needed to order $20 worth of stuff to meet the minimum order... I ordered the parts to fix 2 more tube amps that have been on the bench for months.