Danish Moder RCA roundie

[DaveWM]

https://www.youtube.com/watch?v=gTW2eNFCM_M

should not be too much to get it working well.

[bgk283]

Nice set Dave, caps in the vertical and you should have nice pic, is that the one that was at your dads?

[DaveWM]

yep that's the one. I got a nice packard bell set also not sure if I did a video on already. it was a 23v.

[etype2]

Nice set Dave. I have a CTC15 with a few issues. Would you happen to have a service manual that you could scan and share? I'm a newbie to ownership, but I enjoyed them back in the day.

[DaveWM]

you should look for these two books

tab books vol 1 RCA Color TV service manual. Note vol 1 starts with CTC-12 and covers many later models including the CTC-15. It give great tips and hints as well as a through explanation of how the circuits work.


RCA field service guide for 1955-1966, this has many fold out schematic begining with a CTC-2b thur CTC-20. its useful but I prefer the tab book as it cover not only the schematics but gives a lot more.

[etype2]

Thanks for the referral.

[DaveWM]

FYI, these two books come up on ebay all the time, far too large to scan.

[DaveWM]

I will have some more videos later tonight. I found what I think is the issue on both the vert size and the hum, but alas I did not have the correct cap so had to order, will be a few days before I know for sure.

I did manage to re rivut the speaker (they ALWAYS break) terminal. I also replaced a hacked in wire fix on the chroma board (again a common problem).

a resistor from the boost voltage 150k had drifted up to 2.4 meg, pretty sure that will take care of the height.

an 80uf decoupling cap off the vert out was completely open, this would allow a huge spike to go back into the B+, and mixed with the reg ripple (almost as the vert rate is slightly slower than the line rate) should account for the very slow hum bar. Note the hum bar being VERY slow is a hint here as its the beat of the 59.99 vs 60hrz that is what I think I was seeing.

anyway that all for now.

[Jeffhs]

Originally Posted by DaveWM

I will have some more videos later tonight. I found what I think is the issue on both the vert size and the hum, but alas I did not have the correct cap so had to order, will be a few days before I know for sure.

I did manage to re rivut the speaker (they ALWAYS break) terminal. I also replaced a hacked in wire fix on the chroma board (again a common problem).

a resistor from the boost voltage 150k had drifted up to 2.4 meg, pretty sure that will take care of the height.

an 80uf decoupling cap off the vert out was completely open, this would allow a huge spike to go back into the B+, and mixed with the reg ripple (almost as the vert rate is slightly slower than the line rate) should account for the very slow hum bar. Note the hum bar being VERY slow is a hint here as its the beat of the 59.99 vs 60hrz that is what I think I was seeing.

anyway that all for now.

I had a Sears Silvertone roundie color set (CTC12 clone). It also had the slowly-moving hum bar in the picture the last few weeks of its life (had other problems too--convergence, etc.), but I didn't think it was a capacitor causing the hum at the time. I tried replacing the 6AW8 video output tube, but the replacement, from my junk box, had a bent pin (!) and the socket broke out of the video PC board when I pressed a bit too hard on the tube. If I had known that a defective capacitor could cause this problem, I'd have looked at the chassis, and been a lot more careful replacing the tube if the capacitor were OK. I wound up junking the set when the PC board broke, as I was in no position at the time to do any kind of underchassis work (long story and OT).

[DaveWM]

the new videos are up Pt 2-5.

The sound is a little weak, I will try a new sound detector tube and will go thru the the sound alignment process.

The hum bar (really the beat freq bar of vert and line freq I suppose I should be calling it,hmmm B.F.V.A.L.) is fixed as is the vertical height.

I only replaced the 80uf/2uf can the power supple doublers and filters were fine. The 80uf was the vert decoupler.

[DaveWM]

Done

https://www.youtube.com/watch?v=Rnm9E0kk9vc