Rca CTC-25 overview and help

[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.

[ZenithNut]

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.

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.

[Electronic M]

Originally Posted by ZenithNut

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.

Definitely get a plastic alignment tool and stop using the metal one before you crack your slug... I've been there done that, and can say removing a crack slug without destroying the coil can be a royal pain in the butt... sourcing a new slug can be tricky too.

The only thing you will need to change on your scope is the vertical voltage scale. Composite video is about 1vpp and h osc waveforms in tube set are on the order of 50vpp...
How new your game system is can be important if you plan to use it as a H frequency reference. Older game systems used 240p rather than 525i. That change shifted the horizontal frequency a bit, and while most sets can sync to it I'm leery of using some random spec a programmer came up with because they were too cheap/reasource strapped to create a proper NTSC spec video source.

If you lost video and sound together you probably want to check tuner and IF systems. Wiggle tubes and if you get noise that stage and everything between it and the video detector diode are fine. In some cases the IF lead to the tuner will open or go intermittent... I have a CTC15 clone where the tuner and it's IF lead are permanently connected to the main chassis with soldered wire. The point the IF lead solders to the tuner has no strain relief so when I pull the chassis the center conductor of the IF lead tends to break off of it's tuner solder post... killing both picture and sound.

Do you have raster? If not check your boost voltage. Troubleshooting, adjustment and repair all get easier with the screen lightning.

[ZenithNut]

Originally Posted by Electronic M

Definitely get a plastic alignment tool and stop using the metal one before you crack your slug... I've been there done that, and can say removing a crack slug without destroying the coil can be a royal pain in the butt... sourcing a new slug can be tricky too.

The only thing you will need to change on your scope is the vertical voltage scale. Composite video is about 1vpp and h osc waveforms in tube set are on the order of 50vpp...
How new your game system is can be important if you plan to use it as a H frequency reference. Older game systems used 240p rather than 525i. That change shifted the horizontal frequency a bit, and while most sets can sync to it I'm leery of using some random spec a programmer came up with because they were too cheap/reasource strapped to create a proper NTSC spec video source.

If you lost video and sound together you probably want to check tuner and IF systems. Wiggle tubes and if you get noise that stage and everything between it and the video detector diode are fine. In some cases the IF lead to the tuner will open or go intermittent... I have a CTC15 clone where the tuner and it's IF lead are permanently connected to the main chassis with soldered wire. The point the IF lead solders to the tuner has no strain relief so when I pull the chassis the center conductor of the IF lead tends to break off of it's tuner solder post... killing both picture and sound.

Do you have raster? If not check your boost voltage. Troubleshooting, adjustment and repair all get easier with the screen lightning.

Now that i think of it i dont have the antenna or uhf/vhf cables connected. Ill hook the tunner up as needed. I ended up using my super nintendo to get a nice wave form 9 divisions wide and 30 high. The sams says theres a waveform off pin 8 of the h osc tube. It was thinner and super high/long, not sure what exact words to use to describe it. Ill get a plastic hex as suggested. Since I wont be tunning the slugs with a metal hex ill do as much more as i can in this set then im gonna get (a much simpler) zenith bw tv going chassis 17T20.