RCA Victor 730TV1 Horizontal Problem

[vts1134]

My living room television has developed a problem lately. My horizontal frequency drifts slowly as the set plays. I have to adjust the horizontal hold counter clockwise every so often and end up running out of range after 2 hours or so. Any one have an idea what could cause this?

[miniman82]

Drifty resistor or leaky/gassy tube.

[vts1134]

Resistor I can understand, as the set heats up it starts to change in value. I don't quite understand the tube though, how would a gassy tube change as it heats up? Just trying to understand.

[Kevin Kuehn]

As the tubes inter-electrode impedance's change, so does it's operating characteristics. Similar effect to having a drifting external resistor or capacitor, or a combination of both.

[nasadowsk]

Don't discount capacitors, even Mica types. I recently had an interesting issue with my Bendix, where the picture would shrink and lose focus. This was traced (with freeze spray) to a bad capacitor in the horizontal section.

The technique is simple: Run the set (with access to the chassis underside) until the problem occurs, and then spray a general section of the set until you 'fix' it. Then narrow down your searching area until you find the one component that's heat sensitive. That's the bad one.

Takes time, but it works.

[Gregb]

I just had one doing the same thing on the vertical, it would start to roll and I could correct but after a while would run out of adjustment. It turned out to be a heat sensitive tubular ceramic cap.
Tracked the area down with a heat gun and then my soldering iron held near to each component found the bad cap.

Gregb

[vts1134]

Thanks for the responses guys. I'm going to pull the chassis after I get my VA62 up and running so I can learn alignment while it's on the bench. I'll let you know what I find out.

[Steve McVoy]

I use my soldering iron on resistors and mica capacitors to see if they drift.