two 7" Motorolas (TS-4J)

[Adam]

I decided to fix up all my 7" sets at once and do my Motorolas the same time I'm working on the Airline. Got the 1st Motorola working today.

For the 2nd Motorola, I was going to refinish my other wood cabinet, but now I'm thinking I'll use my suitcase cabinet, rather than having two that are the same. Started with 4 cabinets (3 dark wood, 1 suitcase), 3 chassis (but only enough good parts between them to get 2 working), and 4 7JP4s (1 good in the pic below, 1 very weak, 1 with a dot burned in the center and arcing in the base, 1 currently untested - I'm hoping this is good, otherwise I'm going to take the base off of the arcing one (it appears to be arcing in the base and not actually in the tube) and that burn is hardly noticeable and it's an otherwise bright tube)

In the first picture, that's melted mask material I hadn't yet cleaned off the front of the tube.

[Adam]

It worked for about 10min, then the horiz shrunk a little, then lost sync. The problem was just a horiz osc tube. But strangely, the tube tests ok (just a little weak), I would have not expected it to cause problems. I going to keep this tube, and when I get the next Motorola going, try it in the horizontal and see if it has the same effect. If I swap it with the vertical oscillator tube in this set it works fine in that circuit.

Also when I took the chassis out to see what the problem was this time, I didn't want to pull the 7JP4 out of the cabinet, so I used that one I said was really weak. But sometimes now I turn it on and it comes up ok (not as bright as the other one, but watchable with the lights on), but sometimes it looks very weak. Nothing I do seems to change that after it's powered up, but if I turn it off and on again sometimes it comes up bright, sometimes not. What's going on? The base doesn't appear to be loose. The other 7JP4 always comes up bright, so this must be something with this tube, and not the set.

[Sam Cogley]

Bad solder connection somewhere?

[Adam]

Almost have the 2nd Motorola working. But I can't increase the vert size anymore than in that picture below without getting bad linearity and eventually vertical foldover on the top of the screen.

[bandersen]

Could be a flaky 6SL7 vertical output tube or surrounding circuitry. I've had trouble with that area on a couple sets.

[Adam]

Replaced bad resistor, now I have full vert size. This was one of most broken tvs I've had:
1. missing parts replaced from other chassis: flyback, fine tuning shaft, focus control shaft, most tubes
2. recap of paper and electrolytic capacitors
3. all 3 spare 7JP4s I had were bad, had to get another
4. no horiz = loose wire inside horiz output transformer
5. no sound, bad picture = alignment: both sound and picture, but only the sound was way off
6. horiz sync = bad micas and resistors
7. vert size

[jeyurkon]

Originally Posted by Adam

Replaced bad resistor, now I have full vert size. This was one of most broken tvs I've had:
1. missing parts replaced from other chassis: flyback, fine tuning shaft, focus control shaft, most tubes
2. recap of paper and electrolytic capacitors
3. all 3 spare 7JP4s I had were bad, had to get another
4. no horiz = loose wire inside horiz output transformer
5. no sound, bad picture = alignment: both sound and picture, but only the sound was way off
6. horiz sync = bad micas and resistors
7. vert size

But it feels so good when you've solved all those problems.

[bandersen]

Way to go I've had more trouble working on these little sets than any others.
Looks like Dr Who is on