My Christmas day 9T246 restoration! Almost.....

[Kamakiri]

Originally Posted by earlyfilm

Horizontal sync that locks as the set warms up, but won't relock after a channel change is a relatively common problem on the early RCA sets using this and similar horizontal circuits.

The cause is misadjustment of the multiple controls in horizontal sync.

I don't have a factory schematic on this set, so take look at the Sams 74, fol 8:

http://www.earlytelevision.org/pdf/R...-Sams-74-8.pdf

If the .01 Mfd cap on the exposed end of T3 Horizontal Oscillator coil under the chassis is original, you can bet that this set was taken out of service before it was 10 years old. But, you say, this cap is paralleled by a 22K resistor, how could a little leakage hurt? Well it can cause some well-intended person to mess up the other horizontal sync adjustments!

After you have finished recapping the set, follow the alignment procedure on page 18 of that Sams. If you are lucky, you won't have to use a scope.

Well, the cap was indeed original....all of the wax caps have now been replaced with new mylar jobs. Since the set was working prior to this, I decided to plug it in at this point, and check my work. Everything's up to snuff, and the picture is much crisper than it was.....now for the last leg, the electrolytics.

The issue that brought about earlyfilm's post was my set losing horizontal lock when I change the channel, and having to power down the set for a period of time to get it to lock back in. The picture locks in fine as long as the set is left on the channel that it's set at when I power the set on.

Now I probably shouldn't have done this, but I did it anyway.....without a scope available, I applied the "golden screwdriver" technique, and tweaked B6 all over the place, using the rest of the controls to try to tune everything in......

Well, it worked, kind of. Whereas before I had to power down the set for an hour or longer to get the horizontal to come back, now I just have to flick it on and off, and it pops back into alignment. If I made any improvement, it was by dumb luck more than anything else. Picture size, linearity, etc, all seem close to dead on.

At the moment, the horizontal hold is at the end of its range clockwise....I can now bring it counterclockwise almost 1/2 turn without affecting the picture, and before I had to leave it buried to the right for the picture to lock in.

In the setup procedure, it says "If more than 9 bars are present Just before synchronization, turn the horizontal locking range trimmer (B5) slightly clockwise. If less than 7 bars are present, turn B5 slightly counterclockwise. Turn the hold control counterclockwise and momentarily interrupt the signal and check the number of bars present at the pull-in point. Repeat this procedure until 7 to 9 bars are present."

I never got down that low, there were about a dozen bars at best, maybe 20+ at worst. The horizontal locking range control seemed to have almost no effect on anything.

Something is telling me that I'm dealing with a resistor out of tolerance rather than a setup procedure, but I could be WAY off in that assumption. Thoughts?

[Penthode]

Originally Posted by Kamakiri

Now I probably shouldn't have done this, but I did it anyway.....without a scope available, I applied the "golden screwdriver" technique, and tweaked B6 all over the place, using the rest of the controls to try to tune everything in......

If you have the original RCA notes or the Rider notes, you can find how to adjust the horizontal blocking oscillator transformer without a scope.

The RCA Synchroguide oscillator circuit used by RCA and others for over a decade is quite straightforward to adjust. It comprised of the oscillator tuning adjustment and a separate sine wave stabilization coil. In the earlier sets, these were mounted on the same coil form.

In this set you are first told to short out the stabilzation coil (I believe terminals C and D) and adjust (under the chassis) to frequency. Because it is a blocking oscillator it behaves similarly to the vertical blocking oscillator in the way it locks. The best lock position for the horizontal oscillator is to sync at just the point where the sync bar just disappears to the left with this adjustment.

After adjusting the oscillator, remove the short from C and D. Turn the horizontal hold to the far left, interrupt the signal and you should find the picture out of sync. Adjust the sine coil (from outside of chassis) so that about five to seven bars are seen before it pulls into lock. The adjustments interact so that you may have to go over it a few times.

You can tell if the sine coil is misadjusted: if the sine coil is adjusted to far one way you will get double triggering and you will hear a "chipping" sound when you adjust the horizontal hold. Too far the other way and the noise immunity is lost: verticals in the picture will look coggly on weaker or noisy signals.

I do not think there is likely a resistor problem. You need to ensure the oscillator and sine wave coil are set up correctly first. I would simply leave the locking range trimmer at about 1 1/2 turn from fully clockwise and see to the oscillator first. These adjustments all interact.

Try and find the RCA notes as they are pretty clear on how to do this. Also my memory is not as good as the written notes!

[Kamakiri]

Originally Posted by Penthode

If you have the original RCA notes or the Rider notes, you can find how to adjust the horizontal blocking oscillator transformer without a scope.

The RCA Synchroguide oscillator circuit used by RCA and others for over a decade is quite straightforward to adjust. It comprised of the oscillator tuning adjustment and a separate sine wave stabilization coil. In the earlier sets, these were mounted on the same coil form.

In this set you are first told to short out the stabilzation coil (I believe terminals C and D) and adjust (under the chassis) to frequency. Because it is a blocking oscillator it behaves similarly to the vertical blocking oscillator in the way it locks. The best lock position for the horizontal oscillator is to sync at just the point where the sync bar just disappears to the left with this adjustment.

After adjusting the oscillator, remove the short from C and D. Turn the horizontal hold to the far left, interrupt the signal and you should find the picture out of sync. Adjust the sine coil (from outside of chassis) so that about five to seven bars are seen before it pulls into lock. The adjustments interact so that you may have to go over it a few times.

You can tell if the sine coil is misadjusted: if the sine coil is adjusted to far one way you will get double triggering and you will hear a "chipping" sound when you adjust the horizontal hold. Too far the other way and the noise immunity is lost: verticals in the picture will look coggly on weaker or noisy signals.

I do not think there is likely a resistor problem. You need to ensure the oscillator and sine wave coil are set up correctly first. I would simply leave the locking range trimmer at about 1 1/2 turn from fully clockwise and see to the oscillator first. These adjustments all interact.

Try and find the RCA notes as they are pretty clear on how to do this. Also my memory is not as good as the written notes!

If you ever get down to Buffalo, would you be willing to give me a hand with the adjustments? I'm sure you could claim some of the television booty in my basement to make it well worth your while

In any event, I watched Lawrence Welk on the set last night, and for the hour that the program was on, the set was perfectly stable with a bright picture.....probably because I didn't change the channel

I accidentally replaced a couple 1 kV caps with 630V caps, so I have to go back in there and do that so I'll be able to use it safely. It's shelved for the time being, figured I'd do the cap replacement at the same time as the alignment.