I'm almost embarrassed to be posting this. As I mentioned in another thread, I picked up another metal cabinet Admiral !4YP3B(my 3rd). After recapping it, and new rectifiers, it played good for a few days. Then the horizontal became unstable. I thought after 2 previous restorations, I should be pretty good at these, but it has me stumped. The last one I did developed this problem. After much help from this group, someone asked me what my source was: a VCR. I was directed to quit using that, so I switched to cable, and it cleared up. This set does it on cable as well.

Voltages are all correct on my 6CG7 horiz mult, & 12DQ6 output tube. I have replaced the paper & mica caps and most resistors. What I didn't replace checks ok. I can get the pic to almost sync, but with bar at the extreme right (see pics). Adjusting the horiz hold to try to move the pic further to the right makes it lose horiz sync. I've fought this for a week. One thing: the horiz hold is towards the center of the set (front to back) and has a long plastic shaft attached to it to reach out the back. The coil is stable and checks good (100 ohms), but if I bump that ajdusting shaft, the pic will move horizontally on the screen. Any sugestions?
Thanks
Doug

Might be bad AFC diodes.

You might check the heater voltages of the 5U8 and the 6CG7.

Are you getting the 255 volts at the H hold coil?

I agree, bad diodes. Could also be a sync issue, but I don't have any experience with this type of horizontal circuit.

Ok, here is what I have come up with;

Heater voltages are ok. I had already replaced the pair of diodes (M3).
I'm beginning to think it's a sync issue based on the following voltages on the 5U8 Sync Inv.

Pin Function Voltage SB Acutal without Signal Actual With Signal
1 Plate 215V 232 194
9 Grid 25 16 30
8 cath 32 22 35

Doug

Let me try that again since the 1st post got jumbled up.

Pin 1 is the Plate. I should have 215V. Without a signal I have 232. With a a signal I have 194. The boost voltage SB 255, and I have 264.

Pin 9 is the grid. I should have 25V. Without a signal I have 16, and with a signal I have 30.

Pin 8 is the cathode. I should have 32. Without signal I have 22. With signal I have 35.

Is there a note on the schematic telling you if their measurements were with signal or without? In any case, those measurements do not seem too far off. The voltages on the schematic never match exactly with what you see in a set on the bench.

Is there any chance that you got one of the diodes in backwards?

What did you replace M3 (AFC diodes) with? There is no AFC; did you try changing the local/distance switch position?

I would take a close look around the Sync Separator tube, particularly the circuit between it and the H Oscillator tube, your Horizontal is running at the right frequency, it's just not locking where it should.

I don't have the schematic to look at so I'm just throwing this out there somewhat blindly.

The schematic can be found at
http://www.earlytelevision.org/images/Admiral-14YP3B-Sams-350-1.pdf

Guys, I think I may have isolated my problem, or most of it. When I started recapping this set, several tubes had shields made out of a black, carbon, paper type material. When I tried to remove the these tube to check them, these shelds literally came apart. I didn't bother doing anything about shields. However, today, wehen I decided this issue was more of a sync problem than horizontal one, I began looking at a junker chasis I have of the same model. It used metal shields on those tubes. I then found two metal shoelds and put them on the 6BA8 (sync seperator) and 5U8 (sync inv). The pic is more stable now, but not as stable as I would like it.

To answer the questions: I replaced M3 with 2 signal diodes that I have used on my other two restorations of identical models. The set was displaying the same symptom before and after I did the replacement.
The local/distance switch it set where it gives the best pic for cable: I guess Local.
The schematic does say voltages are taken with NO signal applied. I should have read that before checking voltages.

I'm going to probe around some more on the 6BA8 sync sep tube now.

how did the 100k resistors in the horz afc check?

Dave, I believe I replaced one and the other one checked exact. I've had it playing on and off all evening. I just fired it up again after a 30 min rest. The picture is much more steady now, but still wants to pull occasionally. I did have to tweek the tuning slug on Ch 3 (where my cable plays) and that helped The fine tuning doesn't seem to work. The fine tuning shaft continuously moves and doesn't stop and doesn't have any effect. On my other 2 sets like this, the fine tuning goes so far and stops. I guess someone messed up the fine tuning at one point. My 1st one of these was a set where someone had canabolized the tuner, and I ended up using the set for parts.

Since that TV does not have AGC I think that an overloaded signal may be playing a part in your problems.

I've been playing with this on and off all week. I thought I had found the problem. When Johnnyscan mentioned the overloaded signal, I went back and started tracing at the Video Output. I had overlooked the 6800ohm 2W resistor which had drifted upto 7500. A new one helped some, but not completely. I rechecked the bottom PC board that has the horizontal caps & resistors in it also. The two AFC diodes aren in correctly.

I have noticed this: With the contrast about half way, the pic is as stable as I can get. The horiz does lost sync from time to time then clears back up. But I still have that bar on the right side of the screen. If I try to adjust the horiz hold to move the bar off the screen, the pic loses horiz sync. With full contrast, the pic is wavy and loses horiz sync. At mim contrast, the bar at the right gats larger and moves towards the center of the screen.
Turning the vol upto max sometimes makes this bar get larger too

perhaps you have already addressed this, but did you confirm the polarity of the diodes, I noted they are not common cathode as is used on a lot of sets.

Dave, that would be my 1st guess, but the set was having the same problems with the old diode installed. I think I am using a 1N34A for a signal diode which is what I normally use. However, at this point, I'm willing to try anything. Would you suggest another type of diode?

Doug

well if the polarity is correct then you could check the diodes and see if they are ok. Also I assume you have checked EVERY thing after the diodes to the grid of the osc, there is not much there. I assume you do not have a scope, if you do I would use that to confirm the waveforms.

New parts can be bad. Most any small signal diode should work there, but not rectifiers. I expect that the sync phase inverter stage has to be working correctly because if it were not then the vertical sync would not work (or would be very weak). Are you familiar with how diodes test on an ohmmeter? The meter should show a low resistance with the leads hooked up one way and not move the needle with the leads hooked up the other way. Check several diodes and pick two that measure about the same (that is, select a matched pair).

I like to use my simpson 260 for checking diodes, since it has the polarity reverse knob built in. I look for about a 10 to 1 ratio in the 10x range when switching polarity. Or use a reg modern DMM with the built in diode test, Germainium diodes would be .3v Silicon about .6v, nothing when polarity is reversed. I did not look real close but unless the diodes are isolated by a cap, you will need to lift one leg to do the testing. Like Tom says new stuff can be bad, which is why I always check new diodes, caps, coils and resistors before going in.

I'm still fighting this. One time I can get it to play fairly decent, then the next time I can't hardly do anything with it. Here is a recent pic I took tonight. As you can see, the image is too far to the left. Using the horiz hold will move it to the right and cause the line (at the extreme right) to almost disappear. But then as soon as that happens the hoiz loses sync. The only way to keep it in sync is to have it like that, with the pic too far to the left.

Could that be corrected with the centering rings on the yoke? I've checked everything in that circut from the diodes to the osc grid except two resistors.