Starting work on the Sylvania 7140M

[jeyurkon]

Originally Posted by Eric H

I posted a short video showing what's happening with this set. http://www.youtube.com/watch?v=C9HuJxELL6c

In other news, this set uses one of those integrated circuit type Vertical Integrator things, looks like a large flat Ceramic Disc cap, anyhow the center leg of it is broken completely off the component, I would expect this to only affect the Vertical section since the Sync for the Horiz is taken off immediately before this section.

I can poke the leg back into the hole and it makes a very slight difference in the Vertical but has no apparent affect at all on the Horizontal.
I suppose I'll have to build one of these out of individual parts, it seems to be a very typical Vertical circuit with the 8200 ohm resistors and some small value caps.

It makes so little difference Mad Man Muntz would just cut it out and leave it that way.

I've attached the instructions for adjusting the phase and... It's from a different model, but the procedure is the same.

If V17 the 6AU6 has any grid leakage at all you won't be able to make the adjustment work. Most tube testers won't have enough sensitivity for this test and you need to use a leakage tester.

This set doesn't use feedback from the flyback to control the phasing.

John

Uhh, I just realized the numbers are different. Where it says R90 it should be R226, the ringing coil is L63. B1 should be sticking out the back of the set and B3 should be in the same transformer, but on this inside.

[miniman82]

Looks like the horizontal oscilator never really locks onto anything, it's just drifting through it's range. Looks exactly like my CTC-7 when I couldn't get the chroma demods to work correctly, the colors would just float by and never settle into a stable picture like it should. I suggest you begin looking at your sync seperator section and if that's working as advetised, see if the sync signal is actually making it to the horizontal section.

[Eric H]

Good grief John, you nailed it on the first try.

I swapped out V17 with one of the Sound i.f. tubes and the set started working!

I retested that rube and it checks very good, however bumping up the heater a little made the Short light start to flicker a little, after that it stayed on dimly, testing it the first time it just didn't get hot enough to show up the problem.

The second tube was a even little jittery when tapped so I tried another, now it's really solid.
Those same tubes work fine in the Audio section but I'll replace them anyway.

It's been messed with so much I still need to run through that setup procedure but at least it's working, when I get the new HV rectifiers in I'll try it with the 17" tube.

[bandersen]

Originally Posted by Eric H

Good grief John, you nailed it on the first try.

I swapped out V17 with one of the Sound i.f. tubes and the set started working!

I retested that rube and it checks very good, however bumping up the heater a little made the Short light start to flicker a little, after that it stayed on dimly, testing it the first time it just didn't get hot enough to show up the problem.

The second tube was a even little jittery when tapped so I tried another, now it's really solid.
Those same tubes work fine in the Audio section but I'll replace them anyway.

It's been messed with so much I still need to run through that setup procedure but at least it's working, when I get the new HV rectifiers in I'll try it with the 17" tube.

Sweet Glad you got it working.

I've been finding more and more that tube testers don't tell the whole story. That includes tubes that test weak but work just fine!

[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]

Originally Posted by miniman82

Looks like the horizontal oscilator never really locks onto anything, it's just drifting through it's range. Looks exactly like my CTC-7 when I couldn't get the chroma demods to work correctly, the colors would just float by and never settle into a stable picture like it should. I suggest you begin looking at your sync seperator section and if that's working as advetised, see if the sync signal is actually making it to the horizontal section.

I should have mentioned in my video that i was turning the Oscillator coil back and forth, it would lock, just not where it should.