The CTC-5 Made it to Germany already!

[yagosaga]

Originally Posted by roundscreen

If C127 looks like a brown or tan square disk with color dots on it. Just replace it.

Yes, it looks so. I havbe replaced it with a 1200v d.c. capacitor.

Originally Posted by roundscreen

Did the replacement of the 6CG7 do anything to the horz current?

No. But I have some other news. There is a 1 meg resistor R105 in the schematics between R131 (to the grid of the 6CB5) and the kathode. This 1 meg resistor is missing in this set. I have added it. But now horizontal output current increases up to 230ma. I will cut R105 next time.
Voltage at grid is -22v, but has to be -40v according to the schematics. The resistance between grid chassis ground is appr. 300 - 400 K. This seems to low for me.

[roundscreen]

Vary interesting. On the manual you sent me that resistor shows R165 Someone wrote omit on it in ink. -22v is low. When i get out of work I will measure that voltage on mine and see what i get. If i recall correctly i think it was approx -35v. Also i will take a resistance reading. How is the horz sync? Do you have to turn the knob one complete turn before the horz sync goes out?
Ed

[yagosaga]

Originally Posted by roundscreen

Vary interesting. On the manual you sent me that resistor shows R165 Someone wrote omit on it in ink.

Thank you very much for your support! This manual doesn't belong to this set. But the remarks are interesting, they show me the weak points of the set.

Originally Posted by roundscreen

-22v is low.

While watching the meters during the lunch break, currents increased up to -29v with 200 - 210ma current. I will change R601 (470K) in the evening after work to 800K to see what an effect this has and hope to move the working point of the 6CB5 to the lower flank.

Originally Posted by roundscreen

How is the horz sync? Do you have to turn the knob one complete turn before the horz sync goes out?

Yes. I can turn it one and a half turn before sync goes out.

[yagosaga]

Originally Posted by roundscreen

On the manual you sent me that resistor shows R165 Someone wrote omit on it in ink. -22v is low.

The grid control of V104 (6CB5) is connected over R601 with the brightness control of the set (R101A). This is important to know.
Last night I have changed R601 (470K) with a 900K resistor, horiz. current was only 170-180ma, grid of 6CB5 has -35v to -39v. This seems OK, but brightness is overloading, at minimum brightness control there is full brightness and picture width changes enormously with brightness adjusting.
Later I analysed the horiz. oscillator section. I have already noted that R165 at the grid of 6CB5 is missing. But this was wrong assumption.
They have moved R165 on the Hor. Oscillator Assembly plate (PW 600). "Ground" of R165 is the grid of the 2nd. triode of V601 (6CG7). R165 can switched off/on by a cable link on the printed circuit. (See the blue colored part of the schematics here). I have changed the location of R165 according to the origin schematics of the manual (yellow colored part). But horiz. current exceeded 230ma and grid of 6CB5 has -20v. This was the wrong way. I have restored the origin circuits of the set (with R165 at grid of V601, blue colored part).
At the 2nd. grid of V601 I measured -40v instead of -68v (or maybe -88v, it is not clear printed in the manual). I assume that the oscillator doesn't provide a full amplidute sine wave.

[Bill R]

I checked my field service guide and it shows the resistor connected to the grid of the 6cg7. What you have in blue. The voltage on the grid is -88 volts.

[yagosaga]

Originally Posted by Bill R

I checked my field service guide and it shows the resistor connected to the grid of the 6cg7. What you have in blue. The voltage on the grid is -88 volts.

Thank you very much for that information. Yellow is the layout of my service manuals here (only as pdf-file) and blue is the actual layout of the printed assembly here on the chassis. Note:I have copy and drawn here the blue parts into the photo of the schematics! In this ctc-5 the printed assembly PW600 was changed. This change was not documented in my service guide.
Yesterday I have tested the 6CB5. With 40 percent it was at the lower end of the scale. I have renewed it. Now I read -24v at the grid of the 6CB5, horizontal output current now is 190ma (with 114v ac) and 170mA (with 105v ac, for comparison see my posting of 02-12-2005 12:16 AM). Picture width is wider than the screen in the middle position of the width switch. Flyback is very warm, but not hot after one hour.
At first glance all seems OK now. But I think, -24v at grid of 6CB5 is still not enough. There is too much d.c. in the horizontal output unit. It should be -40v. When I get a new damper I will change it too (usually I change only horizontal output tube and damper together).
At the anode, pin 6 of the 6CG7 (horizontal oscillator, V601), I read 140v, should be 235v according to schematics. At the grid (pin 7 of 6CG7) I read -40v, should be -88v according to the reading in your field service guide. The 6CG7 seems not ok, I have found a short between heating and kathode. But kathode here is connected with the ground of the chassis.

[roundscreen]

Eckhard. please check C611 and C610 82mmf

[roundscreen]

Same thing as before. If they are a brown or tan cap with dots. {Replace them}. They won't be as large as the one in the agc.

[roundscreen]

Replacement of the caps c611-c610 and a horz realignment may help bring up the grid voltage at the 6CB5. Also give the cap off pin 7 of the 6cg7 a check. 270 mmf{pf} I can not read the # of that cap. Sorry about the goofy posts.{kid running around}
ED.

[yagosaga]

Originally Posted by roundscreen

Replacement of the caps c611-c610 and a horz realignment may help bring up the grid voltage at the 6CB5. Also give the cap off pin 7 of the 6cg7 a check. 270 mmf{pf} I can not read the # of that cap. Sorry about the goofy posts.{kid running around}
ED.

No goofy posts but elementary help! Thank you for your support. These caps are the usual suspects... They were already recapped with small brown dotted ceramic caps. But I think the voltage rate seems not high enough, there are high currents in this oscillator unit. And I will change them with higher rated polypropylen caps. I'm just on the way in the city and will got to the next electronic store.

[yagosaga]

This tv set is an exercise in being patient (like most of the vintage sets..)

c611and c610 recapped, c603 too with 0.01 at 2kv. c606 (pin 7, grid of 6CG7) tested OK.
c603 is designed for 1kv. The results: -23v at grid of 6CB5 and horizontal output current 190ma after recapping. The usual suspicious are OK.

Values for the first triode of 6CG7:
!!! The reading of the test meter at the grid (pin 2) is -3v instead of -27v. !!! No sync while contacting with the testmeter - it was not possible to adjust correct synchronisation while testing.
!!! Testmeter at kathode of 6CG7 (pin 3) reads +12.6v instead of +5v. !!! Ohmmeter reads 228K between grid and ground, this seems OK.
Between grid (pin 2) and ground 1.27M, has to be 1.3M according to the manual. OK.
R608 with 156K, OK.
All capacitors on the horizontal oscillator unit are now freshly recapped.
6CG7 used and new, tested with 10ma, good.

c609 has 0.0047 instead of 0.047. The guy, who had done the recapping job before must mistaken it. (Or not?). I replaced c609 with 0.047. Now -18v at grid of 6CB5 and horizontal output current 210ma.
Without c609 I read -22v at grid of 6CB5 and horizontal output current 200ma. What are the correct data for c609?

c604 ist OK with 1000 (or 1nF).

[roundscreen]

I checked c609 on a sams manual and the manual in the computer. Both show .047. C604 is 1000pf . Checked both manuals on c604 too. Dug out the other ctc5.{ctc5e} This set is a junker I got from a buddie who is into radios. He did a re cap and ran the set without checking the horz current and the flyback overheated. He quit and gave it to me. I did a trade for some radios. This set has been a trouble since day one. Never could get the horz size to fill the picture like the other ctc5s and the current was hard to control. Here are some readings on it. AC 110. b+ 292v. Drive voltage -27v. current 205ma. hv 21kv with normal brightness. As you can see b+ and drive voltages are low. Maybe This picture may help you. Throw it on your hard drive and zoom it up. It shows how to adjust the drive voltage. I will do some more work on my set and get more voltage readings on the 6cg7. It was not happy when I turned it on. {Been many years since it was turned on} Have to check the power filters. {may be one reason why the b+ is so low} and the color looks crap. Keep picking at your set like you been doing. I am sure you will get it to work the way you want it to.
ED

[yagosaga]

It seems that the problems of horizontal output are not my problems alone. Thank you for your comment and the scanned page, which helped me to understand how the sawtooth-waveform is generated in the horizontal oscillator. This gave me the kick to check the older RCA chassis too. And what did I found? ctc4 and ct-100 had both a horizontal drive control. The remaining circuits are nearly identical. The 6CB7 have the same kathode grid voltage difference, appr. 50v. But in the ctc-4 there is an extra -29v source in the power supply only for the 6CB5. No grid voltage of the 6CB5 was used for brightness control level like in ctc-5 and no d.c. connection to the grid of the horizontal oscillator. Between c154 (ctc-4) and the grid is only one R160 with 470K to kathode. The ctc-5 seems more puzzling here.

It is interesting to know whether the ctc-4s had the same trouble with high horizontal output currents and low drive voltage at the grid of the 6CB7. Does somebody here has some experiences with the ctc-4? Can somebody here provide the schematics for the ctc-7 or ctc-9?

I have added a 0.047 cap again to c609. At kathode of 6CG7 still I read 12v. But there is very low high voltage but very high focus voltage (it's arcing). With 0.0047 the set is running "properly". Another point: c611 is critical. instead of 82 it was replaced with 100. I have replaced it with 82, and horizontal current increased a little.

The schematics of the ctc-5 are much more interconnected with other units in the set than the former models. One possibility is to insert a drive control like in the ctc-4.
The other possibility is to renew c609 with 0.047 and do a complete re-adjusting of the horizontal oscillator and output unit. On page 17 of the service manual is a method how to adjust horizontal output correctly. I have an old oscilloscope from the 1960's on the attic, which I will arouse again to life for that.

[Steve K]

Eckhard:

Here is the horizontal section of the CTC-7. I also have the schematic for the 9. Is this the only part you wanted to see or would you like the entire schematics?

Steve

[Bill R]

Originally Posted by yagosaga

Values for the first triode of 6CG7:
!!! The reading of the test meter at the grid (pin 2) is -3v instead of -27v. !!! No sync while contacting with the testmeter - it was not possible to adjust correct synchronisation while testing.

!!! Testmeter at kathode of 6CG7 (pin 3) reads +12.6v instead of +5v. !!! Ohmmeter reads 228K between grid and ground, this seems OK.
Between grid (pin 2) and ground 1.27M, has to be 1.3M according to the manual. OK.
R608 with 156K, OK.

c609 has 0.0047 instead of 0.047. The guy, who had done the recapping job before must mistaken it. (Or not?). I replaced c609 with 0.047. Now -18v at grid of 6CB5 and horizontal output current 210ma.
Without c609 I read -22v at grid of 6CB5 and horizontal output current 200ma. What are the correct data for c609?

Are you using a vtvm or dvm to measure the voltage? A vom will load the circuit at pin 2 since it's input resistance is lower than that of the circuit you are testing. You need to use a vtvm or a digital meter or scope to check the voltage at pin 2 of the 6cg7.

R608 shows 100k not 156k.

My guide shows c609 as .047. However they have been known to be wrong.
It certenly seemed to work better with the .0047.

I do notice in the list of production changes that on some sets they omitted R602 the 1 meg resistor.
I also notice that r603 which shows 82k has been 100k 120k and 150k.

What is the plate voltage on pin 1 of the cg7? It should be 300volts? I would double check the values of the resistors in this circuit especially r 608. Resistors are cheep I might just replace them. I know it is shotgunning, but sometimes it is the only way to find something breaking down at full voltage.
I do not think I would add a drive control since none was there in the original design. On the ctc 7 they added a drive control. They lifted the ground end of r603, changed its value to 100k and connected it to .0033 cap then to 250k pot to ground. There are some other changes to the 6cg7 circuit though and it used a 6dq5 output tube.