I inherited Grandma's old Zenith TV set from the early 80s and for the most
part it works like new. However, sometimes when you first turn the set on,
or maybe after a few minutes of use, the picture will turn to snow and
static on every channel. It will stay like this for anywhere from a few
seconds to ten minutes, and then will snap out of it. After this the TV set
will work fine, with no problems whatsoever, until you turn it off and let
it sit for a while. Then it may or may not come back.

I believe there is an intermittant component somewhere that is causing this;
maybe a faulty varistor that won't work properly unless it's at a certain
temp. My belief that this problem lies somewhere in the RF stages, since the
display and audio are fine.

Where would I begin to look for trouble on this set?

I have extensive knowledge of vacuum tube devices, but transistors and
smaller are unfamiliar territory to me.



Regards,

Tim