Quote:
Originally Posted by Electronic M
Since I my CTC-25 info went with my CTC-25 to its new owner I'm kind of flying blind here.
Which slug are you turning? If it is the linearity slug that will have no effect on the frequency and probably very limited effect if any on the H out grid drive waveform.
Are you adjusting the slug with a proper plastic hex adjustment tool? If you use a metal hex key for adjustment you will crack your slug (which will make it feel like it is turning when it is not) in short order.
The general procedure I go on for a rough osc adjustment is this: Connect scope to a composite video source (a VCR or DVD showing a blank screen is nice for this) and tune the scope to show 1-3 cycles of horizontal sync/video lines, count the number of divisions between leading edges of peaks, leave scope H/time settings exactly as they are from here on, connect scope to TVs horizontal osc test points adjust the horizontal osc trans top slug for the correct width of the waveform (make sure peaks are same distance apart as you measured with composite video) then if needed adjust the bottom slug for wave shape in the osc section (don't worry about output grid yet). Generally, I rough in the frequency and wave shape then follow sam's instructions when I have a picture on screen to optimize things. If after adjusting the osc the waveform at the grid of the output tube looks bad check the components between the osc and output.
The osc trans will be next to the H osc tube (usually a 6CG7) on the sweep PCB...There are two slugs in the osc transformer a top (usually freq) and a bottom (usually shape) and they may interact a bit...Some RCAs did a dirty trick and did not give a bottom access hole in the bottom of the board for the lower slug...Instead, to adjust it you had to have a plastic alignment tool that only had a 1/4" or less hex section on the end of the shaft and was narrower than the hex over the rest of the shaft. That tool made it possible to adjust both slugs separately from the top. You can still find those alignment tools for sale online.
One thing to watch out for on RCA per your explanation of the stepped freq behavior is bad PCB solder joints...The worst spots are on the H osc, H lin/efficiency coils, and the board ground to chassis ground joints, and tube sockets that all have a lot of mechanical stress on them. If they crack you will get weird intermittent behavior that makes no sense. I will often reflow them whenever I have weird symptoms. A 75W or higher gun or preferably soldering iron is best for the grounds...Everything else, use a more tame iron for.
That is all the wisdom I've got for tonight. I'm going to bed. Good luck.
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I was tunning the h efficiency coil so that makes sense why there was no change. I do not have a plastic hex. I have an "Ifixit" tool case with the proper size hex end but it is metal.
I dont have a vcr BUT i have a lot of old cartridge based nintendo and sega video game consoles I can use for a composite source. So youre saying to fire up the scope attatched to a blank composite source and then dial in the scope to get a wave form then keep the scope on those setting and attatch the scope to the tv and adjust the h slug to match the wave from a blank input setting from the composite signal of my choice?
I might end up doing some reflowing. I had audio and video before the chassis went on the bench. Now theres no sound or video. All I did was replace a few ecaps and re silicone the fly. Thank you for your help Tom.