I have been having much trouble with the High-voltage and sweep circuits of this set.
Let's start first with a schematic of the set. This is from Rider's TV page 11-16
The schematic is shown here in two overlapping parts.
The trouble happened after much of the recapping had occured. The plate of V117 would glow cherry red, even with the plate cap disconnected.
Something had to be drawing too much current, or the bias on the tube had to be off. I looked to the net for some answers.
Thomas Singletary emailed me with this advice:
As you know, the 6CD6 HOT draws its plate current through the flyback windings. This circuit was marginal in this chassis. The most critical things are: 1. Make sure you have adequate grid drive to the 6CD6 since this is where the bias is derived. 2. Treat the 6CD6 circuit like a resonant RF tank circuit. In other words, place a milliammeter in the cathode circuit and adjust the width coil for MINIMUM current. Another way to do this is to adjust the width coil for MAXIMUM dc voltage on the SCREEN GRID of the 6CD6. This procedure usually prevented the flyback from burning up again. The factory came out with a few additional modifications that added cathode resistance to the HOT. The Merit company made the best flybacks for this model - much better than the original.
So, I proceeded to check components it the circuit of the H. output. I replaced many resistors, and even eventually replaced the flyback, but still, no high voltage, and no filament voltage on the HV rectifier.
In all this I had never thought to check the capacitors I had replaced. I had made a mistake in wiring a new capacitor in, which I had caught in time.
I replaced capacitors in stages, re-installing the chassis in the cabinet and powering it up to watch the changes the new caps made. Capacitors in the Horizontal output were the very last ones to be replaced.
I still had high-voltage and a raster until the last caps were installed. Then I began checking over and over the connections I had made and compared them with the wiring diagram for my version of the chassis. I never thought to check that I had installed the correct values until....
I emailed a friend in the Navy who was into electronics. A few days later (yesterday) she called me and asked me a few questions about my problem. After many questions and a decision to make this page to try and explain what's going on, I decided to haul that 50-pound chassis out of its cabinet for another look. In my poking and prodding I found a capacitor, C190, that was the wrong value. It is supposed to be .0015 mfd, but the one I installed was .015 mfd.
This cap was also in the cathode circuit of the V117 horizontal sweep output. I don't know how big a difference the wrong value has made, but I do know it was one of those last 5 caps that was replaced.
Other parts that I have replaced (and triple-triple-checked for accuracy) in the horizontal section:
I will be ordering a new C190 from Antique Electronic Supply soon.
Here is a discussion on deflection circuits from RC-19 (RCA Tube Manual)