Back to the VT-71H

[Yamamaya42]

I'm just going on speculation here, never having worked on a electrostatic type set myself yet, but assuming that bias power and video is clean, winch really can't be done with the naked eye from a troubleshooting standpoint, but if so, you would have to go over every inch of the sync separator circuit (or as it's called, clipper here.) from where it's taken off the video amp circuit to where it's processed, and fed to the horizontal / vertical OSCs, making sure that all in between is correct and in tolerance.

[timmy]

Got a perfect picture now however when it warms up the vertical size collapses and gets jittery and lines across mostly the bottom and some on top. I tried the retrace mod and it gets rid of slot of lines but the size problem is still there.

[Chris K]

Don’t know if this will help Tim but there might be an issue with the CRT socket at pin 2. When I was troubleshooting the video loss I noticed the full screen raster I had collapsed when I moved the tube in such a way that the wire going to pin 2 got flexed at an angle approaching 90 degrees to the socket. That’s why there’s heat shrink on it to stiffen it up. I’m just throwing that out there in case there’s some issue with that connection when the CRT gets warm. I can’t remember if the vertical collapsed to a horizontal line or the screen went dark when this happened. In any case, there may, emphasis on may, be an issue with the CRT socket at pin 2 connection.

[timmy]

Originally Posted by Chris K

Don’t know if this will help Tim but there might be an issue with the CRT socket at pin 2. When I was troubleshooting the video loss I noticed the full screen raster I had collapsed when I moved the tube in such a way that the wire going to pin 2 got flexed at an angle approaching 90 degrees to the socket. That’s why there’s heat shrink on it to stiffen it up. I’m just throwing that out there in case there’s some issue with that connection when the CRT gets warm. I can’t remember if the vertical collapsed to a horizontal line or the screen went dark when this happened. In any case, there may, emphasis on may, be an issue with the CRT socket at pin 2 connection.

Yes I noticed that but I managed to pinch the pin tighter and it’s been ok. But according to the schematic there is supposed to be a .1 cap at the 6sl7 .05 to .1 to ground but I’m not finding the .1 so idk if this was a run change for this chassis who knows but I’m going to tack one in and see if the vertical size comes back to life.

[bandersen]

No, it's not a run change. That cap needs to be there. I suspect you just found the problem.

[timmy]

Originally Posted by bandersen

No, it's not a run change. That cap needs to be there. I suspect you just found the problem.

Yes I found it but I still looking for the reason why if I use vertical size to widen the screen up and down sometimes it goes and other times it don’t but it’s got vertical lines on the bottom and some on top but very unstable it rolls but it does stop with the hold pot this almost seems to be a bad cap or wrong cap I don’t know. The .004 cap was replaced with a .0047 I wouldn’t have put that in since the .004 is available. Oh and I reversed the 1n34 diode and got a perfect picture except for the lines and instability in vertical. I thought I had a decent picture befor I reversed the diode but now it’s perfect now have to figure what’s going on with vertical.

[Chris K]

Originally Posted by timmy

Yes I found it but I still looking for the reason why if I use vertical size to widen the screen up and down sometimes it goes and other times it don’t but it’s got vertical lines on the bottom and some on top but very unstable it rolls but it does stop with the hold pot this almost seems to be a bad cap or wrong cap I don’t know. The .004 cap was replaced with a .0047 I wouldn’t have put that in since the .004 is available. Oh and I reversed the 1n34 diode and got a perfect picture except for the lines and instability in vertical. I thought I had a decent picture befor I reversed the diode but now it’s perfect now have to figure what’s going on with vertical.

The detector diode is a strange trip. In the TS-4H schematic I have it was installed correctly. I had it in the direction you now have it but reversed it when I saw the schematic. The original 1N34 was installed the way u now have the replacement wired so IDK…these TVs have a lot of variability

[timmy]

Originally Posted by Chris K

The detector diode is a strange trip. In the TS-4H schematic I have it was installed correctly. I had it in the direction you now have it but reversed it when I saw the schematic. The original 1N34 was installed the way u now have the replacement wired so IDK…these TVs have a lot of variability

The original was put in the opposite of the way the schematic shows? That’s how I have it now and the b+ voltages came up good.

[Chris K]

Just forget it! I even confused myself, when I read what I wrote!

[bandersen]

I just got one of these working last night. Maybe this video will inspire? https://youtu.be/WiFyS_SVpeM

[timmy]

Originally Posted by bandersen

I just got one of these working last night. Maybe this video will inspire? https://youtu.be/WiFyS_SVpeM

Nice video I was hoping you may have had a problem with vertical size lol

[Chris K]

Originally Posted by bandersen

I just got one of these working last night. Maybe this video will inspire? https://youtu.be/WiFyS_SVpeM

I wish I had ordered the Adapt-a-caps before I did the electrolytic re-cap on this. They look so clean. I'm using them on the Dumont Doghouse RA-103 and they look great, even mounted under the chassis as the TV has cans in some very hard to get to places for top mounting them.

[bandersen]

Funny you mention RA103. You'll like my next video

[Chris K]

Originally Posted by bandersen

Funny you mention RA103. You'll like my next video

That’ll be great! I got the replacement relay but someone already did some “bodging” to get around it…but that’s for the other thread.

[timmy]

Certain scenes the picture has lines across the top other scenes it disappears I wonder if it’s the 4 caps in the vertical or maybe a .005 cap.