View Full Version : RCA Round tube 4.43Mhz ntsc/pal color TV advice please


BRC2000
09-13-2016, 03:37 AM
Hi I am restoring a RCA rca CTC16 which was modified by RCA for 240v 625 line 4.43Mhz NTSC / PAL see
http://www.vintage-radio.net/forum/showthread.php?t=129430
I now have the TV working in both color standards but still have problems which people on your forum probably have experience of.
One the height reduces as it heats up.
Two the horizontal lock drifts and is poor.
Both tubes have been changed.
Thanks
Keith

radiomec
09-13-2016, 04:12 AM
It's quite normal that changing the vertical frequency there is a variation in linearity and height, because 50 or 60 Hz is quite different. If you want have an equal picture in both the standards, you should put an relay that exchanges different trimmers for height and linearity controls. Instead 15750 or 15625 Hz are not very different, however to change some capacitors for these two standards would be better.

Electronic M
09-13-2016, 07:37 AM
How many of the caps are original? The orange and maroon drops of the era don't fail shorted like papers, but instead fail high ESR/open. I'd probably replace the drop style caps in the sweep stages as a precaution.

It should NOT have variation in height or lin with warmup...Here in the states there is an old TV serviceman's trick for troubleshooting this. Let the set warmup till it is doing it noticeably, get a can of freeze spray (canned air for dusting should work too), and shoot individual caps and resistors in the suspected stage one at a time (vert stage) until you see the problem correct it's self...The part or parts that when sprayed correct the issue are prone to excessive thermal drift and should be replaced.

bluenorm
09-13-2016, 11:53 AM
there is a resistor between the vertical centering and/or the vertical height that when faulty ( I replaced about 10 years ago following advice from this forum however I do not remember witch one) some times produces the same symptoms. in my case I was having the same issue. replaced and was able to correct all adjustments. r104?

BRC2000
09-14-2016, 03:20 AM
Only the color decoder is dual standard the time bases are single standard 625 line only. The problem is the height is correct when cold and reduces as it heats up.
I assumed that the maroon drops would be OK so I will start by changing them.
Thanks
Keith

miniman82
09-16-2016, 09:00 AM
If it has decent vert/horizontal lock the film caps are probably fine, I've never found a a bad maroon drop but anything is possible is suppose. The shrinking vertical is likely a drifting resistor that feeds the vertical circuit from its B+boost source, so follow the wiring and locate the resistor in between them. Often times I find the value of that dropping resistor needs adjustment, even from stated schematic values in order to achieve a full height raster. Could also be the height pot is out of spec, so check its value.

roundscreen
09-27-2016, 08:18 AM
replace all the electrolytic caps. sooner or later they are going to fail and cause problems. Your set has a nice picture .

andy
09-27-2016, 12:26 PM
I would start by checking all of the resistors in the vertical circuit. Those carbon composition resistors tend to increase in value. They're also temperature sensitive, so if one has drifted to the edge of its tolerance, some heat could push it over the edge. If it still has a problem after replacing any bad resistors, I would try using a can of freeze spray.

dieseljeep
09-30-2016, 11:09 AM
Hi I am restoring a RCA rca CTC16 which was modified by RCA for 240v 625 line 4.43Mhz NTSC / PAL see
http://www.vintage-radio.net/forum/showthread.php?t=129430
I now have the TV working in both color standards but still have problems which people on your forum probably have experience of.
One the height reduces as it heats up.
Two the horizontal lock drifts and is poor.
Both tubes have been changed.
Thanks
Keith

The set still has a great picture, considering it has the original CRT!
Of all the RCA roundies, the CTC16E & X is my favorite. They seemed to be, just a little more refined!
The CTC16X had the rare-earth CRT. The picture quality was a bit better, but the CRT's in the 16E's were great, as well.

Penthode
10-03-2016, 10:24 PM
I would start by checking all of the resistors in the vertical circuit. Those carbon composition resistors tend to increase in value. They're also temperature sensitive, so if one has drifted to the edge of its tolerance, some heat could push it over the edge. If it still has a problem after replacing any bad resistors, I would try using a can of freeze spray.

Funny, I had the same shrinking vertical sweep problem. Also the picture would roll as it warmed up. I ended up changing all of the carbon composition resitors in the sweep circuit and it is as good a new: the sweep remains constant and no more roll as it warms up!

Findm-Keepm
10-04-2016, 08:52 AM
First, make sure the 6GF7 cathode cap has been replaced. For the 50uF, use a 47uf - works well in my CTC16. Second, the 5.6K cathode resistor is known to cause shrinking problems.

Lastly - look at all the resistors in the 6GF7 area - lots of heat, and they tend to drift. Metal Oxide types work well as replacement. As my Dad use to say, any resistor in the vertical circuit of an RCA is suspect.....many service notes point to the higher - k ohm resistors in the horizontal as well. Check and replace any valued at 100K or higher - the 150K's in my CTC16 height control circuit were all swapped at some point.

BRC2000
10-17-2016, 04:30 AM
Hi All
Update on the RCA16 thank you for the advice I found that most of the 100k plus resistors high and these were replaced also c511,c512 and c138 were leaky and also replaced. When c138 was replaced I had no picture because cr101 was open circuit this was replaced with a BY140 and I now have a brighter picture and full hight with no reduction with heat. I have also replaced sr501a/sr501b and have good horizontal lock.
Thanks
Keith