Horizontally Segmented Picture

[earlyfilm]

Originally Posted by Giulio Maiocco

. . . . . . the problem may be spurious oscillations in the vertical section . . . . . . .

Exactly!

What I think is happening here is electrically the same thing that motor-boating is to a vacuum tube audio power amplifier, and the same checks will usually work. In both cases, for pre-1960's equipment, it is most likely in the output stage, but can be anywhere in a related circuit.

The problem here is this Delco Auto TV is probably a proof of conception prototype, most likely made to determine if the public would buy one if GM offered a car TV for sale. This prototype only had to work well enough for display and there is no known documentation on the set, including what voltages the missing power supply provided.

Since this spurious signal is probably happening in the vertical output area, the scope will be of little use here. If Bob cannot localize the problem, he may have to find a TV restorer locally who has a scope and is familiar with the older vertical circuits, but that is the last resort.

Bob, I forgot to mention earlier, if there is an electrolytic across the cathode resister of the vertical output tube or in the plate circuit and/or screen grid of the vertical output, make sure they are good. This test can be made by simply jumping them with a second electrolytic, since over capacity here should not do any harm.

James

Edited to delete incorrect assumption. I incorrectly remembered that GM completely switched from subcontractors to made-in-house auto radios as 1953 or 1954.