Hallicrafter 509 image shifted horizontally

[ohohyodafarted]

Well, I was able to devise a method to get the chassis powered up and in a position where I can work on the underside. I traced the video path with my scope. It disappeared at the 1st video amp 6v6. During my work I inadvertently lifted the grounded side of the filament ckt at the 6v6. (this is the kind of dumb stuff you do while working at 4AM when you should be sleeping) Video is now back with the video image shifted by 1/2 screen and the vertical bar in the center is still there.

Next step is to use my scope with the info that Kevin Kuehn posted and see what my scope discovers. Hopefully this will lead to discovering the problem.

[Kevin Kuehn]

Just out of curiosity does the horizontal hold work normally, as in can you move the picture slightly left or right before losing horizontal lock? You should have the horizontal hold control centered when you make the horizontal oscillator coil adjustment. Ordinarily you wouldn't need to move the slug far to get lock unless someone previously messed it up. While you have your scope in there verify that the saw tooth frequency at the grid of the horizontal output tube is correct.

[ohohyodafarted]

Originally Posted by Kevin Kuehn

Just out of curiosity does the horizontal hold work normally, as in can you move the picture slightly left or right t before losing horizontal lock? You should have the horizontal hold control centered when you make the horizontal oscillator coil adjustment. Ordinarily you wouldn't need to move the slug far to get lock unless someone previously messed it up. While you have your scope in there verify that the saw tooth frequency at the grid of the horizontal output tube is correct.

Yes the H hold works normally. I have the Horizontal hold control optimized at the center of it's range, and when you adjust the control the stable image (and the vertical band) will shift slightly left and right depending on which way you turn the control. IE: it seems to be working perfectly normal.

Next step is to start looking at the wave forms in the article you posted.

BTW, what should the frequency be, at the grid of the 6BG6? 15.734 Khz?

I may not get to that today. Got some other things I need to do.

Thanks for your help,
Bob G.

[Kevin Kuehn]

Originally Posted by ohohyodafarted

BTW, what should the frequency be, at the grid of the 6BG6? 15.734 Khz?

15,750 Khz.

[old_tv_nut]

if the image is a single image (it is) and is not skewed diagonally (it's not) [as shown], the frequency is correct. No need to try measuring it. Only the phase is wrong.

[Electronic M]

Originally Posted by old_tv_nut

if the image is a single image (it is) and is not skewed diagonally (it's not) [as shown], the frequency is correct. No need to try measuring it. Only the phase is wrong.

I agree with old TV nut.

Some counters are tricked by the non-sinusoidal horizontal waveforms so I typically adjust horizontal frequency by first measuring scope divisions between leading edges of horizontal sync pluses in a digital composite video source (DVD player, DTV converter, etc) then adjusting the vintage TV H osc for the same number of scope horizontal divisions between peaks (and usually the peak slightly higher than the hump on synchroguide based circuits) works well.... Probably not needed here, but useful if your frequency counter gets confused on complex waveshapes.

[Kevin Kuehn]

Originally Posted by old_tv_nut

if the image is a single image (it is) and is not skewed diagonally (it's not) [as shown], the frequency is correct. No need to try measuring it. Only the phase is wrong.

Is it not possible to have the horizontal oscillator adjusted wrong and still be locked, but out of phase?

[old_tv_nut]

Originally Posted by Kevin Kuehn

Is it not possible to have the horizontal oscillator adjusted wrong and still be locked, but out of phase?

There are two things happening.
1) The oscillator is locked. The phase locked loop is basically functioning. The free running horizontal frequency may be off center, but it is within the pull-in range of the loop.
2) It is locked at the wrong phase and is stable at the wrong phase. This should not happen whether the free-running horizontal frequency is correct or not.

Note that when the loop is locked, adjusting the free-running frequency +/- will rock the phase back and forth a bit to generate the correction voltage that keeps the locked frequency correct. This effect can be seen when the circuit locks at the correct phase as normal or the incorrect phase as shown here.

Something is making the control voltage out of the phase detector correct when the phase is 180 degrees from normal.

[Username1]

.

Hi!

If you have a nice locked picture, then what happened is that you made a mistake
with replacing parts and the sync is getting to the H Osc. out of phase, or delayed
because there are 2 parts in the wrong spot and an RC is charging & discharging
in a way to delay the sync and it's showing up in the middle of the screen.
It's locked to the sync pulse as you can see it's pretty perfectly straight.
I think the best way to find this is to Check the wiring, Look for wrong
parts in wrong spots, etc.

.

[Kevin Kuehn]

Originally Posted by old_tv_nut

Something is making the control voltage out of the phase detector correct when the phase is 180 degrees from normal.

Component wise there's not much in the path to mess things up. I suppose if the two 1500pf mica?(domino looking) caps that connect the +/- sync inverter pulses to the sync discriminator have not been changed I'd go for those. If one or both are leaky it could potentially offset the DC control bias going to the horizontal oscillator grid. Also check the two 100k discriminator resistors for balance.

[ohohyodafarted]

Thanks to all who made suggestions

I took Kevin Kuehn's suggestion and measured the grid of the Horiz output tube 6BG6. It had a nice saw-tooth waveform, but when I calculated the pulse width on my scope it appeared that it was running about 1/2 speed at about 7800HZ.

From there I figured that something had to be amiss in the horizontal oscillator section. So I started testing values. I found a bad mica cap across the H freq coil that was shorted, and I replaced it. That did not fix the problem so I kept testing. Then I found a 270K (R87 on the hallicrafter schematic) that had drifted to 780K. I replaced it and the oscilator speed just about doubled. After tweaking the H-Oscilator freq coil, the picture came into sync and I had a perfect full picture.

Again thanks to all that contributed. So many knowledgeable techs that know a lot more than I do.

Bob Galanter