[Tom Albrecht]

N2IXK,

I have a Ringer, but it works poorly. I've been on the lookout to buy a better one, but that's one acquisition I still need to make. The one I have has a sticky meter movement, and I have not been able to improve it. That ends up making the readings very unreliable. Would be nice to have a good Ringer right now, just to make doubly sure that the problem isn't somewhere else and the flyback really shows the expected lossy behavior in a Ringer.

Miniman,

I'm actually reasonably experienced at TV restoration, so quite a few of the important things you point out are indeed things I already paid attention to, or have reasons to believe are not relevant for the particular way I'm going after the problem. Nonetheless, I'm glad to see you ask all the right questions here, since I don't want to leave out something critical and make an unnecessary mistake.

The horizontal frequency is correct, because I can see just enough video stuff on the screen to tell that it actually locks weakly to a TV signal on the antenna input. Nonetheless, I got out the frequency counter to make sure, and yes, it's ~15.75 kHz. My ear had also confirmed from the start that the pitch was "about right."

HO grid bias is -46 volts, and the peak-to-peak drive waveform is 150 V on the grid (cf. 120 V P-P in Sams), adjustable with the drive control.

HO cathode current is 193 mA (cf. 167 mA in Sams), which seems reasonable given the improper power dissipation in the flyback itself, although if any of these numbers raise a red flag for any of you, don't hesitate to speak up.

The real smoking gun on suspecting the problem is a shorted turn in the HV winding of the flyback transformer is that it is getting quite hot in about 1 minute of operation, with neither the high voltage rectifier (3A3) or focus rectifier (1X2) connected. The only way there can be a load on the high voltage winding is if the load is within the coil itself - a shorted turn or something else very lossy. The heat really does seem to be generated in the HV secondary winding; it is much hotter to the touch than the primary windings. My finger may not be a 100% reliable temperature sensor, however, so I've checked it many times and I seem to be coming to a consistent conclusion on that.

I have the convergence transformer out of circuit for all of these measurements (by disconnecting the focus rectifier), so even though it looks quite likely that it is bad, it can wait until the HV problem is cured. It is definitely not having any effect on the flyback right now.

I have the CRT out of circuit most of the time, but have connected it a few times (as well as the 3A3 HV rectifier) and can see a very dim, out-of-focus raster on the screen, and it does not substantially load down the already weak HV (because the CRT anode current is almost zero under these circumstances). HV is quite low, around 10-13 kV -- a little lower in that range yesterday, a little higher today. No evidence of any current in the 6BD4 regulator tube (which is how it should be with the HV too low). Disconnecting or connecting the regulator tube has no effect (which indicates it is working correctly, or at least doing no harm).

I think I'm properly covering all the things that could account for improper flyback function, but if you see something I missed, I'll be more than happy to go after it. I, too, am not eager to prematurely modify the flyback in an irreversible manner.

One could always suspect the yoke, but if it's bad, it shouldn't be causing my HV secondary on the flyback to get hot. I have a test yoke I can connect, and perhaps I'll do that next just to make sure (in case my finger temp measurements are misleading me as to what's the source of the heat in the flyback).

On the other hand, there are lots of other circuits in the set that have nothing to do with the horizontal sweep, and my preference is to solve this problem before going after all those. I'm confident we'll get this set fixed in a step-by-step manner, and for me, horizontal sweep and HV are priority #1 pretty much in any set I work on. So indeed I agree with you that the horizontal oscillator needs to be functioning properly as step #1, and that was indeed done here.

When I get to the color circuitry, that's where I've got the most learning to do. I've restored dozens and dozens of black and white sets, so I've got a decent grasp of all of the circuitry and functions in black and white sets. But color is something new, so that part of this experience is going to be educational!