Scored ANOTHER 25DC56!

[TUD1]

Keep in mind that the problem is intermittent. One minute the picture is perfect, and the next thing you know, it's snowy and distorted.

[Electronic M]

Originally Posted by TUD1

Keep in mind that the problem is intermittent. One minute the picture is perfect, and the next thing you know, it's snowy and distorted.

I've had intermitent video out put transistors in Zeniths of that era. Screen would change tint towards a primary. Damn thing bugged me for years cause it would not stay bad long enough to meter for a source...Eventually it did and I confirmed my suspicion by switching the three color video out transistors around...When the primary color of the intermittent changed I knew I'd found the culprit. Was mechanically/electrically sensitive too a smack would sometimes fix it, sometimes adjusting the tuner would fix it.

[jr_tech]

Indeed, almost any component can become intermittent, including solder joints as well as active components. Sometimes heating, cooling or mechanically stressing the suspect part will provide an answer, sometimes "blanket replacement" in the suspected area of the circuit is necessary. There is also a possibility that the problem is further downstream, like in the IF amp or AGC circuits. Can you substitute another tuner or do you have a pattern generator that can provide an IF output, and eliminate the tuner from the test?

jr

[zeno]

First off can you get the pix back by hitting, moving
tuner etc ?? OR once snowy do you have to shut off
& cool down to get it back ? Also is it clean snow like
an OTA fringe station ? Last time this came up here
it was just the external matching transformer !!

The set almost has to have a Zenith SGVG tuner that
is good cause its easy to service. BUT I would NOT change
the RF amp without proof. Too many things can go wrong.
Much more info & trouble shooting are needed first.

73 Zeno
LFOD !