Question about measuring and setting horizontal frequency

[Aperna1985]

Hey guys I'm trying to troubleshoot the horizontal section in my RCA KCS- GF2 chassis. It seems like my horizontal hold is just way off frequency. Originally I was thinking of doing is hooking up my scope to try to get the same waveform the Sam's uses. The other day I was watching an older Shango video and he mentioned that the horizontal section should be running at 15 MHz. This got me thinking I use an older analog scope that doesn't have megahertz displayed. It uses a Time base with a USec, MiliSec, and Second scale. I'm not sure how that would really convert over to megahertz. I like my scope and didn't really want to replace it and I've been reading a lot of bad reviews about all those Chinese Scopes out there. So I was thinking could I use either a frequency counter, or a Tiny SA Ultra to try and measure the frequency it's running at, then adjust it to get in the ballpark of where I should be? From there I could try using the Sam's directions.

I uploaded a video onto YouTube of what it's doing right now

https://youtu.be/YeJtLkf1SVc?si=6u6bW_piU-tBBzAg

[Penthode]

The horizontal sweep frequency is nominally 15,750 Hertz. That is 15.75 kiloHertz not MegaHertz.

It is easily measurable on a reasonably calibrated triggered time base oscilloscope. Remember frequency = 1/period. The 15,750Hz frequency equates to a horizontal sweep time of nominally 64 microseconds per line. Simply set the time per division setting to say 20 microseconds per division and when the horizontal frequency is correct, the sweep signal will repeat every 3.2 divisions.

[Penthode]

Also, when adjusting the RCA synchroguide transformer, it is best to short out the ringing coil I believe terminals C and D first. After putting the the oscillator on frequency, remove the short then use the scope and follow the service notes to achieve the proper waveform. If you do not first short out the ringing coil when first adjusting frequency, it may cause spurious triggering and instability. Leaky paper capacitors and drifted carbon composition resistors plague this circuit so if after following the above you cannot achieve the correct frequency, check the components and the tube (especially if the resistors and capacitors have not been checked already!)

[Aperna1985]

Originally Posted by Penthode

Also, when adjusting the RCA synchroguide transformer, it is best to short out the ringing coil I believe terminals C and D first. Then when on frequency, use the scope and follow the service notes to achieve the proper waveform. If not, the ringing coil can cause spurious triggering and instability. Leaky paper capacitors and drifted carbon composition resistors plague this circuit so if after following the above you cannot achieve the correct frequency, check the components and the tube (especially if the resistors and capacitors have not been checked already!)

Sams mentions shorting out a coil in the setup section. I don't have it in front of me but I'll check when I get home. So if I get the wave to look right on the scope and set it around 20microseconds I should be right at that 15.7khz goal?

Sorry for all the questions I'm trying to learn....

[Penthode]

Yep that is about all. Keep us posted. Except when adjusting for correct frequency with the ringing coil shorted, look to see the waveform repeats every 3.2 divisions when the scope is set to 20 us per division. The shape of the waveform is unimportant at this stage.

[zeno]

Pix looks like there is zero H or V sync.
No vert sync gives a vert blanking bar that floats either way but not lock in.
No H sync looks the same. Pix floats with a solid blanking bar.
Your vid shows the H freq barely off. You just cant lock it in for more than a few secs.

SO since its both look at the sync sep stage.
BTW manuals usually show TWO complete cycles of the frame or line.
A lot of modern scopes ( 70's +) have a TV-H & TV-V setting to make it easy !

73 Zeno
LFOD !

[old_tv_nut]

Originally Posted by zeno

Your vid shows the H freq barely off. ..

73 Zeno
LFOD !

I think the coarse diagonal bars are shutter bars from the camera taking the video - note they blink out and return suddenly. So, the horizontal frequency may be way off as well as sync being bad.

Check to see if the vertical sync is really off or not by turning the vertical hold back and forth to see if the vertical locks.

[Aperna1985]

Originally Posted by zeno

Pix looks like there is zero H or V sync.
No vert sync gives a vert blanking bar that floats either way but not lock in.
No H sync looks the same. Pix floats with a solid blanking bar.
Your vid shows the H freq barely off. You just cant lock it in for more than a few secs.

SO since its both look at the sync sep stage.
BTW manuals usually show TWO complete cycles of the frame or line.
A lot of modern scopes ( 70's +) have a TV-H & TV-V setting to make it easy !

73 Zeno
LFOD !

I'm using a Tektronix 531A, it's as old as the TV so it doesn't have it.

[Aperna1985]

Originally Posted by old_tv_nut

I think the coarse diagonal bars are shutter bars from the camera taking the video - note they blink out and return suddenly. So, the horizontal frequency may be way off as well as sync being bad.

Check to see if the vertical sync is really off or not by turning the vertical hold back and forth to see if the vertical locks.

The wide black bars are from the camera. I think the vertical is locking. I'm like 80% because I can see it kind of stop rolling as I play with the control.

[old_tv_nut]

Originally Posted by Aperna1985

The wide black bars are from the camera. I think the vertical is locking. I'm like 80% because I can see it kind of stop rolling as I play with the control.

OK - back to checking horizontal frequency then.