Motorola VT-71 TS-4D Horizontal Jittering Image

[ChrisW6ATV]

OK, I doubt that the 10% difference in value would affect the jitter problem, and if your set is working the same (no better, but also no worse), then they may be fine. Thanks for the update.

[Jon F]

Originally Posted by Paul Knaack

Hello Jon,
First off, I am not experienced or qualified enough to give anyone advise on fixing thier tv, but I do like to try to learn from these forums. So, for what its worth, my thought is could it be the crystal diode in the 2nd detector getting leaky?

Hi, I am not sure. I don't have any 1N34's on hand only 1N4007. They are cheap enough however might be worth a try.

I have also attached an image of the chassis as it is now.

[ChrisW6ATV]

I have still not got back into my TS-4D VT-71, but Decojoe made this comment in another discussion of VT-71s, so I have to wonder how widespread this issue is:

Originally Posted by decojoe67

Nice work! I've only had one of these Motorola's that had a real crisp picture on it. My current set, and others I've had, have that "sizzling" or "pie-crusting". Not bad from a distance, but up close rather low definition.

[ChrisW6ATV]

Here is a close-up picture showing the problem as it appears on my set. It is being fed from a digital-TV converter on channel 3 or 4, with direct RG-6 coax into a matching transformer attached to the antenna terminals. (The picture shows up rotated 90 degrees, and I don't know how to fix that; I even made a copy and re-uploaded it.)

[timmy]

that is a verticle problem , i have 3 of these sets i restored and i would suggest looking close at the verticle section including micas in the verticle there are several for that section. i had the same lines you have there and i changed the micas in the verticle after i recapped the set thinking they were alright. looks like the frequency is off alittle seemingly consistant with one of those micas. i listened to everyone telling me that micas rarely go bad, well they do and they went bad on all 3 sets i got. there are 2 dog bones off the 6sl7 which can be replaced with ceramic discs, and the tie strip to the right of the 6sl7 there is another dog bone. the vert hold pot , there is a tie strap there in that area which has 1 mica and 1 dogbone, they should be changed as well. the chassis in 1 set i got which gave me the worst headache was the ts4d. and if you go back and change those micas and dog bones you should also go back and tweek the channel 3 coils, IIRC there is another coil there that will have to be tweeked as well there is not only 1. i wouldnt use a 1n4007 in place of the 1n34. whats up with those blue caps in the hv section there, there should be all those white caps.

[Electronic M]

I'd first suspect an HV arc/corona issue....I've seen that type of issue on electromagnetic deflection sets when the HV is arcing.

Micas most often go bad in the deflection section (where they take the most abuse), so they should be on the list under the "after everything else tests good or has been replaced in the ____sweep circuits if problems remain change the ____" heading. Never change RF/IF stage micas without first PROVING they are bad.

[timmy]

Rf & if I agree but take a look at the pic of the chassis, different caps for the vert and horiz, not a good match......

[ChrisW6ATV]

Originally Posted by Electronic M

I'd first suspect an HV arc/corona issue....I've seen that type of issue on electromagnetic deflection sets when the HV is arcing.

The one catch with that is how, if the set is adjusted for a "horizontal split picture" as mentioned earlier in the discussion, the jitter goes away (and Jon was able to get the same effect on his set). Very odd. (That should reasonably rule out a weak/noisy signal too, it seems to me, but maybe not.)

[ChrisW6ATV]

Originally Posted by timmy

Rf & if I agree but take a look at the pic of the chassis, different caps for the vert and horiz, not a good match......

That picture is of Jon's chassis; I used ASC tubular capacitors for all of my HV replacements and have the same problem.