1981 19" RCA XL-100 CTC108C no brightness after CRT cleaning

[damen]

If you have an issue with the vertical size,meaning, can't fill the screen with the size control, or, the picture is too tall and can't be pulled in, it may be necessary to replace the resistor for the vertical return circuit from the yoke. It's R522,a 1.8 ohm 2 watt in your 108 chassis, and R518, a 1 ohm resistor in the 118. Just swap them.

[joe111671]

I changed the yoke wiring right at the yoke, cleaned up the donor crt and installed it. The vertical was not filled out all the way, which wasn't unexpected based on Damen's point about the resistor values. There were retrace lines & the picture looked green deficient. No strange sounds or smells though. The focus looked good but I adjusted it anyway.

I setup the gray scale according to the Sams instructions and it came out nice. The height control filled it all the way out with some room to spare. The wiring came out good so I'm calling this a success.

Next I want to put the ashtray set back together and see what that does. I'm curious if everything is the opposite of how this looked at first.

Once again thanks for the advice guys.

[wa2ise]

Maybe you could have swapped the chassis of the ash tray set into the older set cabinet. To be reunited with the CRT from the ash tray set. That would take care of the vertical height issue. The tuners might be an issue, but they all have a standard IF frequency. Only issue might be supply voltages, but you probably can create workarounds for that. But it sounds like you made the ashtray CRT work with teh CTC108 chassis.

Originally Posted by JohnCT

Yeah, it was a short run of flybacks in the 1981 model year. I was surprised when I got a call from a customer with a ColorTrak 2000 I had sold him that went dead. I thought it was a nuisance call but was surprised to find the horiz output shorted. Put in a new one and blam. I figured the retrace cap must have been open (like those GEs did), but the cap was good. Stunned to find a bad flyback.

According to our field rep, it had something to do with a bad batch of epoxy used to encapsulate the transformer.

John

I worked for RCA Sarnoff Labs back then. The flyback transformers used six windings, and 3 diodes to create the very high voltage for the CRT. They thought they could get away with just the 3 diodes, cheaper. Wrong! The terminations of the windings and diodes were a stake style, which created electrostatic stress points. Had they used 6 diodes, one diode per winding (winding-diode-winding-diode-winding-diode-winding-diode-winding-diode-winding-diode) these stresses would have been half as intense, and the flyback transformer would not have failed. When they made the 6 diode flyback, they used a different color epoxy than what they used in the 3 diode flybacks.

I had a CTC101 and loved the picture it made. It had the line comb filter, for better chroma-luma separation (something I did a lot of work and patents on at the RCA Labs). Unfortunately, that CTC101 did have the bad flyback, but it lasted about 10 years before shorting out...

[JohnCT]

Originally Posted by wa2ise

The flyback transformers used six windings, and 3 diodes to create the very high voltage for the CRT. They thought they could get away with just the 3 diodes, cheaper. Wrong! The terminations of the windings and diodes were a stake style, which created electrostatic stress points. Had they used 6 diodes, one diode per winding (winding-diode-winding-diode-winding-diode-winding-diode-winding-diode-winding-diode) these stresses would have been half as intense, and the flyback transformer would not have failed. When they made the 6 diode flyback, they used a different color epoxy than what they used in the 3 diode flybacks.

The diodes would certainly explain it. I do know that a lot of them failed in warranty and that RCA fixed it immediately. Once they did, I cannot recall any integrated flybacks failing until the 177 and 195, and even those were rare.

I did warranty work for RCA in the 80s, and until the 140 went into production in the late 80s (1987?), we had gone many years without making a single claim to RCA for warranty work. When the 140 came out, we had a couple of issues with them (GREAT performer) and we had to call RCA to get the procedure to submit claims.

John

[joe111671]

The swap looks like a double success, they are both now running with each other's crt & yokes. There was just the gray scale setup and that vertical height issue, one needed to be increased & the other reduced, and now they're good. The rejuvenated crt definitely doesn't have the focus of the one out of the CTC118 so I'm glad I took the chance. It's hard to explain but it's like there are halos around bright text, and the focus control gets rid of that, but at the expense of taking everything else out of focus.

Originally Posted by wa2ise

Maybe you could have swapped the chassis of the ash tray set into the older set cabinet.

I almost tried that, but decided to see if the crt swap would work. I actually felt more intimidated by trying to get the tuners swapped, but it worked out and was good experience. I'll keep the chassis out of it just in case, unless someone wants the whole set.

[joe111671]

Originally Posted by damen

If you have an issue with the vertical size,meaning, can't fill the screen with the size control, or, the picture is too tall and can't be pulled in, it may be necessary to replace the resistor for the vertical return circuit from the yoke. It's R522,a 1.8 ohm 2 watt in your 108 chassis, and R518, a 1 ohm resistor in the 118. Just swap them.

The vert size on the CTC108 filled out by adjusting the control, but I noticed that it's not centered, it's down too far. I can't find any way to center it by looking through the Sams. Do you think swapping these resistors will have an effect on the centering? Or is there some provision for adjusting it that I can't find?

[damen]

I don't know if that resistor would affect centering or not. You could parallel the 1.8 ohm resistor with another 2 ohm resistor temporarily under the board to see if bringing the value down to 1 ohm helps or not.