RCA 21-D-7177 Horz Drive Issues

[Penthode]

Hi Kevin,

That is interesting. One extra thing: your set uses the synchroguide horizontal oscillator control. The optimum sync position is with the horizontal hold turned to the right just before it loses sync. If the range of your horizontal hold is not sufficient, then you can turn the hold control fully right and slightly adjust the horizontal frequency slightly so that it just loses sync and back up so it is in sync.

If you have to adjust the coil, make sure you adjust slightly the frequency coil end and not the horizontal waveform adjustment on the other end.

Can you still not see the black stripe on the left? If not then we will have to investigate the retrace time.

Terry

[Kevin Kuehn]

Originally Posted by Penthode

Hi Kevin,

That is interesting. One extra thing: your set uses the synchroguide horizontal oscillator control. The optimum sync position is with the horizontal hold turned to the right just before it loses sync. If the range of your horizontal hold is not sufficient, then you can turn the hold control fully right and slightly adjust the horizontal frequency slightly so that it just loses sync and back up so it is in sync.

If you have to adjust the coil, make sure you adjust slightly the frequency coil end and not the horizontal waveform adjustment on the other end.

Can you still not see the black stripe on the left? If not then we will have to investigate the retrace time.

Terry

Terry,

I'm not so sure this TV uses that exact horiz oscillator circuit. Take a look at the schematic below. I don't see the separate horiz frequency control you speak of. All I have are the horiz hold, and the horiz waveform controls. The horiz hold on this set is a coil (L40 on the schematic). RCA called this a deluxe model TV, but it sure seems to be missing a few key circuit adjusting controls.

[Penthode]

Hi Kevin,

Thanks for the diagram. It is a synchroguide circuit. Only the horizontal hold control isn't a portentiometer in your set: the control is the coil itself. If I recall correctly, your set may have a limter to prevent adjusting it too far. Try adjusting the horizontal hold so that the image moves to the right at the point just before it loses sync. That is the optimum point in a synchroguide circuit and that should provide a good reference to examine the left hand of the picture.

Is it possible to post the damper circuit?

Thanks,

terry

[Kevin Kuehn]

Here's the damper section. Hope it's enough.

[Kevin Kuehn]

Ok... with the horiz hold adjusted so that the picture is farthest to the right(before loss of horiz hold), there is still no dark bar present on the left side of the picture.

I can see both sides of the picture as the set warms up and the picture slowly expands across the screen. There is clearly a bar on the right side.

I did recieve in the mail this week a set of Merit replacement yoke and flyback transformers. I've yet to try those. I'm not looking forward to replacing the flyback. I'll try the yoke after I wire up a new octal plug for it. I may also need to order a new balancing cap for half the horiz winding.

[Kevin Kuehn]

This is interesting: With the line voltage turned down to around 85-90 volts, we do seem to have a black bar on both sides. But I'm also seeing some waving of the scan lines over on the left. You can also clearly see the horizontal linearity is off.

BTW, this is now using the little 8XP4 crt.

[Penthode]

Reducing the line voltage provides a clue. The reduced line voltage will lead to reduced horizontal drive. There might very well be a problem with the flyback transformer. But, I wonder if it is simply a matter of too much horizontal drive?

Have you tried reducing the drive and increase the width?

Terry