CTC38 blue bleeding around edges - Videokarma.org TV - Video

maxhifi · #1 01-03-2020, 10:08 PM

I've noticed an issue lately with my CTC38. On the right hand side of some high contrast images, there is a blue bleeding effect, where It did not do this previously, and I have been using it quite a lot lately. I do not believe it to be a convergence issue. I have the RCA service info, but I'm curious if anyone recognizes this as a symptom of a specific component failure.

old_tv_nut · #2 01-04-2020, 09:13 AM

If it's only on bright white details, and goes away as soon as you turn down the contrast, it's a CRT related issue - G2 adjustment or CRT wearing out, etc.

If it's on everything, bright or not, it's convergence.

zeno · #3 01-04-2020, 05:10 PM

Streaking to the right of brite object usually is weak CRT.
Pix will improve overall at reduced contrast & brite.
Grey scale will usually change with brite adjs. Pix will
improve as set warms up.

Blue convergence on a strong CRT will show yellow cross hatch
with blue cross hatch near it. Just gotta overlap them.

There are some things you can try if it proves to be the CRT.
Best to do a set-up after 1/2 hr warm up then watch in a dark room
at reduced brite & contrast for best pix.

73 Zeno

LFOD !

maxhifi · #4 01-05-2020, 10:59 AM

Unbelievably, it seemed to clear up almost completely by of all things, adjusting the fine tuning control. Get it wrong one way, and it bleeds blue, the other way bleeds green, and right on has only the faintest and smallest shadow, visible only up close. Someone must have touched the knob, I keep it set permanently to CH3 and did not think to adjust fine tuning.

Convergence is fine, and picture tube is strong. I intentionally keep brightness down a bit to prolong life, since the TV is our main TV and we usually watch it after dark.

zeno · #5 01-05-2020, 01:40 PM

I was the jig man & I did more CTC38 than any chassis. Dont remember
a problem like that. Sounds like one of those "something is just off a little"
problems that you wouldnt chase down unless the customer saw it.
Of course you gotta watch the 6GH8's & the sockets on them. The
forward pair of sockets often were bad after a few miles & I changed many.

73 Zeno

LFOD !

maxhifi · #6 01-05-2020, 10:11 PM

Ahh bad sockets? Forward in which direction? The tube which has been an issue in this TV is the sync 6GH8, I have changed it twice since I got the set.

old_tv_nut · #7 01-05-2020, 10:18 PM

Quote:

Originally Posted by maxhifi

Unbelievably, it seemed to clear up almost completely by of all things, adjusting the fine tuning control. Get it wrong one way, and it bleeds blue, the other way bleeds green, and right on has only the faintest and smallest shadow, visible only up close. Someone must have touched the knob, I keep it set permanently to CH3 and did not think to adjust fine tuning.

Convergence is fine, and picture tube is strong. I intentionally keep brightness down a bit to prolong life, since the TV is our main TV and we usually watch it after dark.

Glad you found it. When you said "bleeding" without a picture of it, it was hard to interpret. But if it's a fine tuning issue, maybe you were talking about cross-color or chroma phase distortion, both of which can change with fine tuning. Glad it's fixed. Now, whatever it was, if you see it in the future, you know what to do, no matter what you call it.

maxhifi · #8 01-06-2020, 07:35 AM

Quote:

Originally Posted by old_tv_nut

Glad you found it. When you said "bleeding" without a picture of it, it was hard to interpret. But if it's a fine tuning issue, maybe you were talking about cross-color or chroma phase distortion, both of which can change with fine tuning. Glad it's fixed. Now, whatever it was, if you see it in the future, you know what to do, no matter what you call it.

I think I should make a video next time rather than try to describe it, it really looked like something was wrong with the TV. I have not seen fine tuning affect colour in the same way on other TV sets. Yesterday the TV was on all evening though, working perfectly with no issues.

zeno · #9 01-06-2020, 08:39 AM

Its the 2 on the forward board with the IF's. they have vieo, sync & AGC
IIRC. A fresh tube will fool you with a fix but soon gives problems
again. Easy to change with the right socket. Just dike them apart
& pull one pin at a time like teeth.

maxhifi · #10 01-06-2020, 09:41 AM

Quote:

Originally Posted by zeno

Its the 2 on the forward board with the IF's. they have vieo, sync & AGC
IIRC. A fresh tube will fool you with a fix but soon gives problems
again. Easy to change with the right socket. Just dike them apart
& pull one pin at a time like teeth.

The two tubes in the red rectangle? The one which I changed twice, is V202, the symptom was loss of horizontal lock. I changed it first in 2014, and again in 2019. The tube I changed was a replacement RCA tube, which had been changed by an RCA service center some time in the 70s. The TV was very low hours when I got it. I should order a couple sockets to have on hand, I would never have suspected the socket itself could go bad. V202 seems to run quite hot, but since the set works properly I just sort of assumed that must be normal.

zeno · #11 01-06-2020, 03:28 PM

Yes they are the ones. Also try GE or Zenith ( GE made EIA 188 IIRC) tubes.
The RCA replacements wasnt as good. We used to buy the Zeniths by the
gross for 29 cents, list was near $3 IIRC.

Zeno

Quote:

Originally Posted by maxhifi

The two tubes in the red rectangle? The one which I changed twice, is V202, the symptom was loss of horizontal lock. I changed it first in 2014, and again in 2019. The tube I changed was a replacement RCA tube, which had been changed by an RCA service center some time in the 70s. The TV was very low hours when I got it. I should order a couple sockets to have on hand, I would never have suspected the socket itself could go bad. V202 seems to run quite hot, but since the set works properly I just sort of assumed that must be normal.

maxhifi · #12 01-06-2020, 04:02 PM

Quote:

Originally Posted by zeno

Yes they are the ones. Also try GE or Zenith ( GE made EIA 188 IIRC) tubes.
The RCA replacements wasnt as good. We used to buy the Zeniths by the
gross for 29 cents, list was near $3 IIRC.

Zeno

I bought 2 each of RCA, GE, and Sylvania to use as replacements. The GE I put in there now though, is labeled "Made in Gt. Britain"... not sure which European tube is equivalent to a 6GH8, but must be one. Hopefully the British tube is more reliable than the Sylvania it replaced, and the original RCA tube.

Wish I could get some now for 29 cents, this set uses 5 of them!