Slow vertical drift
 

About two of three years ago I rebuilt a Motorola TS-4J /VT71. Lots of new resistors, all the paper caps, and afew odd things I found along the way. Set worked great for acouple of years and then devoloped a vertical drift probem after about 15 minuntes of use. All voltages around the vert and sycn circuits look good and are steady. Tried frezze spray on the mica caps and also tried heat from a heat gun to get it to act up.
Any ideas?
Terry

I replace all Micas now in my restos. Hell, they're 60 years old.

Considering what they control, it's worth the bother to replace them with Epoxy Micas. Make sure you get the voltage ratings right. Some of the early sets Micas are 1000 volt rated.

LJB:smoke:

It's not clear what drifts; size, position, frequency?

If it is vertical hold, replace the 12SN7 and the timing cap off the vertical hold control. When freeze doesn't help, suspect a tube.

Size is ok. The vertical frequency seems to be drifting causing the picture to roll. I can readjust the vert hold but after a few minuntes it's rolling again. Then it will get out of range of the vert hold pot. Did swap tube no such luck. I'm not that lucky! I'll give that timing cap a try.
Tnx Terry

I had the same problem with my 24" Muntz. I posted a question like yours and got some good help.

Go to post #25 in this thread about my Muntz.

http://audiokarma.org/forums/showthr...=126224&page=2


Good luck,
Bob