CTC5 Pickup!

[old_tv_nut]

"So what am I missing... How do I open up the front service panel? Mine seems to be really stuck and I don't want to break it off. Can't check the horizonatal hold or screen controls until its opened!."

SAMS says remove 5 push-on knobs, then remove two metal screws. (The screws are missing from mine, so I only have to remove the knobs.)

Do not pull down on the wire springs in the top of the control box - these are for releasing the safety glass.

[old_tv_nut]

Get SAMS and RCA literature at
https://www.earlytelevision.org/tv_s...color.html#rca

[Davala]

I can't even get into the control panel to remove the push on knobs. Door will not pop out.


EDIT: I asked my wife for help. She got the door popped open pushing the button and using a screwdriver.

[Penthode]

Push down the center golf tab and with a plastic credit card insert at the top and gentle pry open. I suspect the hinges are slightly rusted and binding.

Once the door is open, you can fix the hinge pins and free it up.

[old_tv_nut]

There was a recommended mod to change the CTC-5 contrast circuit to the CTC-7 version.
https://videokarma.org/showthread.ph...=ctc5+contrast

[zeno]

If the on/off /vc is a mallory easy to fix. Find Mallory KR8M & KR9M
I remember them in early 60's RCA. Others had repair kits but I never did them.
See hear https://www.ebay.com/p/2216531325

Manuals are like following bread crumbs. PCB's Golden Rods, supplaments
etc. Trouble is they always go MIA. Most shops didnt take the time to
keep there library up to snuff.

BTW nice catch & sweet cabinet !

73 Zeno
LFOD !

[Davala]

Originally Posted by old_tv_nut

There was a recommended mod to change the CTC-5 contrast circuit to the CTC-7 version.
https://videokarma.org/showthread.ph...=ctc5+contrast

Thanks for the info. Sure looks like they got it close to the proper ctc7 modification. They went with a 25MFD instead of a 50..

Thanks again,
Matt Davala

[Davala]

After a full recap I finally powered it up this afternoon. Full raster with good width and vertical. But of course I have an issue with brightness and I'm sure its that darn CTC-7 mod. Brightness is on near full at minimum and increasing it loads down the HV at max. I did verify the parts were as they should according to the mod. Even though the mod is for the contrast I assume it affects the brightness to some point. I have now 50 MFD instead of 25MFD from the wiper of the contrast to ground. The previous tech only added a 25 while the CTC 7 mod calls for 50mfd.

I'll pull the chassis again and do some measurements of the brightness circuit as well as the contrast circuit. If everything checks ok I might revert back to the stock CTC-5 contrast circuit and see what effect it has on brightness and go on troubleshooting from there.

Any other ideas? BTW agc and sync were out of wack but I'm sure thats because the video output was being driven really hard.
It also seems that DHR4863 was unable to fix his CTC-5 issue. Unfortunately it sounds exactly like my issue....
--
Matt Davala

[damen]

Have you followed the instructions in the service manual for setting the screens and background controls? The directions are different than those for sets that have a service switch.

[Davala]

Originally Posted by damen

Have you followed the instructions in the service manual for setting the screens and background controls? The directions are different than those for sets that have a service switch.

Thanks for the reply. I did go through the manual and got the brightness level settled in. Interesting relationship between the background and screen controls.

Setting convergence on this thing is a pain! I accidentally pushed a coil trimmer screw for one of the convergence settings past the threads. Watching the screen and twisting I didn't realize it was at the bottom of the threads already. Got to pull the chassis for that.

No color coming through. I adjusted the killer control but saw no change to the bars. I'll see what I can tweak from the topside but I'm assuming I'll be pulling the chassis for that too.

Tuner, IF, video, audio and the deflection all seem to be working. Darn chroma!

Thanks guys,
Matt Davala

[Yamamaya42]

“Vertical hold requires about half a dozen adjustments until it warms then its stable.”

Looking at the schematic, one can see why, at some point between the CTC 11-> 15, RCA added a voltage dependent resistor into the mix, this no doubt made it more stable and robust and less susceptible to instability as the parts aged.

[Penthode]

In my Whitby I had a lot of problems with vertical sweep. The vertical hold drift I fixed by changing resistors. I found found the original very temperature sensitive.

[Davala]

Originally Posted by Penthode

In my Whitby I had a lot of problems with vertical sweep. The vertical hold drift I fixed by changing resistors. I found the original very temperature sensitive.

I'll be pulling the chassis again today and I'll replace resistors in the vertical section.

Did you have any trouble with the chroma section? Seems my 3.58 oscillator isn't running at all since there is zero color.

--
Matt Davala

[Penthode]

Originally Posted by Davala

I'll be pulling the chassis again today and I'll replace resistors in the vertical section.

Did you have any trouble with the chroma section? Seems my 3.58 oscillator isn't running at all since there is zero color.

--
Matt Davala

You will notice in the Deluxe chassis a high wattage power resistor dropper I recall either in the oscillator or chroma bandpass amp section. The power dissipation created a lot of heat which damaged the resistor it self and a coil. I repaired it by mounting a lower value resistor in its place to reduce the dissipation and mounted another power resistor elsewhere on the chassis in series to allow it to dissipate the bulk of the power without burning up anything around it.
You will see the resistor I am talking about. Check it is not open and if there are any charred components around it.

[Davala]

Originally Posted by Penthode

You will notice in the Deluxe chassis a high wattage power resistor dropper I recall either in the oscillator or chroma bandpass amp section. The power dissipation created a lot of heat which damaged the resistor it self and a coil. I repaired it by mounting a lower value resistor in its place to reduce the dissipation and mounted another power resistor elsewhere on the chassis in series to allow it to dissipate the bulk of the power without burning up anything around it.
You will see the resistor I am talking about. Check it is not open and if there are any charred components around it.

I'm pretty sure that's the one that went open on my set. I'll check the coil for continuity. The chassis above the resistor is definitely darkened. It's interesting the sams and rca service info differ on the value of the resistor and what B+ voltage is tapped. Sams has a 390V B+ to a 10k 7 watt resistor yet the RCA service has 300V B+ and 6.8k 7 watt. Mine had the 6.8k and I installed it closer to the chassis to help dissipate its heat better.

--
Matt Davala