Starting work on the Sylvania 7140M

[Eric H]

Well it's 4:45am and I couldn't sleep so I thought I'd post a little more on the progress.

Another tube that tube testers really can't tell you much about is the 5U4, both of the ones in this set checked good but weren't really.

They are wired in Parallel in this set so you can pull one out and the set keeps on working, I pulled the first one out and it kept working fine, a little picture shrinkage and the sound dropped a bit but nothing dramatic.

I put the first 5U4 back in and pulled the second, well, a huge difference, the picture shrank and dimmed almost to the point of disappearing!

I scrounged up another tube from another set and tried it, now the picture was stable on either 5U4 but a little better on the replacement tube so I scrounged another one, now it worked well on either tube by itself.

This also increased the High Voltage substantially, it's running 12k with the picture adjusted to normal brightness, it still drops if I crank the brightness way up but I believe it has enough oomph to try the 17" tube in it.

The Horizontal is working pretty well but it still drifts after a while so that it gets a ghosting or fold over creeping in from the left side of the screen after a while, I can adjust it out but it comes back. I still need to run the setup but there may be a resistor drifting a little after it gets hot, I'll poke around more tomorrow and see what I can find, I'll try the big CRT also, I'd like to see how it looks even though it checks good.

[old_coot88]

Originally Posted by Eric H

...The Horizontal is working pretty well but it still drifts after a while so that it gets a ghosting or fold over creeping in from the left side of the screen after a while, I can adjust it out but it comes back.

Have you verified that the 6AL5 phase detector (discriminator) is good and that it's lighting up? That would be the first thing to verify based on the symptoms you describe. Bill(oc)

[jeyurkon]

Originally Posted by old_coot88

Have you verified that the 6AL5 phase detector (discriminator) is good and that it's lighting up? That would be the first thing to verify based on the symptoms you describe. Bill(oc)

The 4.3 ohm resistor in series with the heater for that tube might have shifted value also. But it might be more stable once you go through the setup.

[Eric H]

This set is getting on my nerves.

I flipped it up and started checking resistors, nothing really far out so I moved on to heat stressing capacitors.

When I got to C197 on the 6AL5 V16 I could get the Horiz smearing to come and go across the screen as I heated or cooled the Cap, it was a Micamold and I am pretty sure it is Mica, anyhow I swapped it out with something close from a junk chassis, I let it play for a good half hour or more and the problem seemed fixed.

I decided to clean up the mess in the Flyback cage, solder in the 10KV caps correctly and fix the wiring on the width coil.

In the process of fixing the width coil I reversed the polarity on it, I didn't know if that would matter but it seems to matter a lot.

After I put the big CRT back in and fired it up I had several terrible drive lines on the right half of the screen, I was able to adjust them out except one bad one in the dead center of the screen.
I noted that I had to screw the slug nearly all the way out instead of nearly all the way in like it was before I switched the coil around.

Does it make sense that reversing the coil would have this effect? I'm not even 100% sure it's the correct coils ince it's been replaced but I didn't have any serious drive line problems before, there was a little ringing on the left side though.

This picture was taken before I did all that stuff, note the smearing through the picture. Not it doesn't smear but it had a bright lin down the center of the pic and faces distort when the pass through it.