RCA CTC39XBJ alignment and tweak. - Page 2 - Videokarma.org TV - Video

freakaftr8 · #16 08-29-2019, 12:10 AM

I tried to snapshot the picture where the top of the raster is brighter than the bottom. It just gradually goes from where you can see greyscale at the top to where its pitch black at the bottom if you adjust the brightness to do so.

Looks to me like it could be a drifted resistor in the video output circuit but not quite sure yet. Has anyone run across this before?

A few years back my 19" Zenith chromacolor 2 had an issue where the horizontal brightness drifted from one side to the other but this is kind of like that but vertical. The Zenith turned out to be a leaky capacitor.

Tried to snapshot this issue.

It can really be seen when watching 16:9 format. There's a visible greyscale at the top, black at the bottom.

freakaftr8 · #17 08-31-2019, 02:17 AM

Well I was watching this thing tonight I decided to tune into some old Colombo, the picture starts acting up. First like a little rf interference look to it and then loss of vertical lock, then all went to hell. Scrambled picture like irs off fine tuning. Think it ate a tuner tube or something in 1st video amp. Was too quick to be a capacitor.

freakaftr8 · #18 08-31-2019, 12:54 PM

Yay a challenge. Something surely drifted in the 1st video/ AGC sync circuit. If I let the set cool overnight, picture is perfect I. The morning for only 30 seconds or so. Then it starts getting RF interference look and goes completely out of whack.

I checked the nuvistor in the tuner. It's good. Tubes in the video amp and RF test good.

freakaftr8 · #19 08-31-2019, 01:37 PM

That was easy. Really crusty flaky 300 ohm / 75 ohm splitter on the input terminal strip. Very odd that it just suddenly happened. Also temperature change seemed to affect it.

Popester · #20 09-01-2019, 05:47 PM

Are you talking splitter or a 300 ohm to 75 ohm matching transformer that goes to the VHF antenna terminals?

freakaftr8 · #21 09-01-2019, 05:56 PM

Yes. This thing, the splitter link. It was very oxidized. Threw me for a loop..

freakaftr8 · #22 09-29-2019, 04:05 AM

Figured it was a nice night to watch a ballgame... I'm impressed with how good the picture quality is with this one! It's right up there with my CTC17 i photographed a few years back. Think I'm ready to call this one a project finished.

All in all, 2 6GH8'S, some IF tubes, convergence and purity, a few out of tolerance resistors in the IF and AGC, and a cleanup of the malfunctioning 75/300 ohm transformer splitter and a bit of VHF tuner cleaning.

Need a power knob and a bulb for the VHF. Mine is split.

This is really a great performing set!

maxhifi · #23 10-01-2019, 09:53 AM

Quote:

Originally Posted by freakaftr8

Figured it was a nice night to watch a ballgame... I'm impressed with how good the picture quality is with this one! It's right up there with my CTC17 i photographed a few years back. Think I'm ready to call this one a project finished.

All in all, 2 6GH8'S, some IF tubes, convergence and purity, a few out of tolerance resistors in the IF and AGC, and a cleanup of the malfunctioning 75/300 ohm transformer splitter and a bit of VHF tuner cleaning.

Need a power knob and a bulb for the VHF. Mine is split.

This is really a great performing set!

Looks great! Shango066 just posted a video about a CTC38X, on youtube.. his also has a great picture. I am surprised this chassis got the reputation as having a bad picture quality.

freakaftr8 · #24 10-04-2019, 10:15 AM

Yep. I really have to say that this one produces the best color picture I have ever seen on a tube set! The 38/39 was the end of the line for the vacuum tube chassis, and I have had XL100 sets that looked great, but this one looks better.

I watched his video. Of course this can all go to the crapper if the CRT is weak.. On my other post about the CTC16, mine produces a soft image. I had another 16 that produced an image close to my 39..