RCA CTC7 colour TV set - UK Vintage Radio Repair and Restoration Discussion Forum

FERNSEH · 8th Oct 2007, 9:39 pm

On Saturday evening I promised myself and others that I would do something about the shop. Smarten the place up.The task in hand was to lay a new carpet.
Anyway, I couldn't be bothered to do that so I decided to reposition the CRT in my 1958/9 RCA CTC7 colour TV set. The blue gun was not in a fully vertical position so it was out with the tube and refit it correctly. What a scary job! The CRT is an RCA all glass round type 21FBP22. My problem was refitting the CRT on to the mask, it did after moving the CRT about, carefully rocking it from side to side Finally it plopped into place.

My set is called the "Abington" model number 21CD872. I cannot send any pictures right now.

A picture of the set appears on Ed Reitans excellent color TV website:

http://novia.net/~ereitan/Gallery/im...bington300.gif

The set was kindly donated to my collection by Mr. Steve McVoy.

DFWB.

System A · 8th Oct 2007, 9:47 pm

Hi David
That set looks great! Does it have a metal shield that holds the degaussing coils in place, as in British sets? Will the set need much to get it going?
Regards. Gary.

FERNSEH · 8th Oct 2007, 10:27 pm

Quote:

Originally Posted by System A

Hi David
That set looks great! Does it have a metal shield that holds the degaussing coils in place, as in British sets? Will the set need much to get it going?
Regards. Gary.

Hi Gary,
According to the service information I have, all RCA colour TVs up to the CTC15 series required the use of an external degaussing coil.
Receivers fitted with the CTC16 chassis of 1964 and later models were equipped with an automatic degauss system. A metal shield was fitted around the CRT cone. Some metal cabinet CTC16 sets were not equipped with automatic degaussing.
My metal cabinet CTC7 does not have a metal shield on the CRT cone. All the wood cabinet versions are fitted with a kinescope (CRT) shield.

Call around on Saturday and see the set working.

DFWB.

Dr-Watts · 10th Oct 2007, 1:15 pm

Ah, early Colour (or Color)

You just can't beat it

I'd also love to see some pictures... pretty please

Dr. Dave

FERNSEH · 10th Oct 2007, 10:13 pm

Quote:

Originally Posted by Dr-Watts

Ah, early Colour (or Color)

You just can't beat it

I'd also love to see some pictures... pretty please

Dr. Dave

You will soon. But first I must either repair or replace my digital camera.

A few notes about the CTC7 colour TV. The luma drive to the cathodes of the CRT comes from a 12BY7A, a valve which similar to the European PL802. For the color difference drives to the control grids of the CRT two 12BH7A twin triodes are employed. Three of the triodes are the CDA amplifiers and one serves as the line blanker. The 3.58mc subcarrier oscillator valve is a 6U8A (ECF82). The triode section is the reaction control and the pentode is the crystal controlled oscillator.
Early production CTC7 (1957/8) receivers employed two 5U4GB valves as the HT rectifiers and later sets (1958/9) used two silicon diodes for the HT supply.
Some sets are fitted with a UHF tuner. The UHF tuners are different to the valve tuners found in early UK made sets. Only one valve is used, a 6AF4A triode which is the oscillator. A 1N82A crystal diode serves as the mixer. As no RF amplifier is used in these tuners I wonder how sensitive these one valve tuners were?

DFWB.

System A · 14th Oct 2007, 8:01 pm

Hi Everyone!

I spent a great morning at FERNSEH's shop yesterday, we put together his RCA Victor color TV. Here are some pictures of the set. Before I left FERNSEH's, we had hiss from the speaker but no line output. Maybe FERNSEH can update us.

Regards,

Gary.

FERNSEH · 14th Oct 2007, 10:18 pm

Hi Gary,
It seems that the line oscillator has stopped working and the lack of line drive to the 6DQ5 line output valve has caused that valve to fail.
I'm OK for bits for the line oscillator as I have a spare chassis. The line oscillator is assembled on a small PCB and employs one valve, a 6CG7 twin triode. One triode is used in a blocking oscillator circuit and the other is the control valve.

Apart from the types of valves employed in this receiver in the line output and EHT stage, the circuit will be familar to those interested in UK and continental hybrid colour TVs. All the valves except for the 1V2 focus diode have international octal bases. The EHT rectifier is a 3A3 which is similar to the GY501 and the EHT shunt stabiliser is a 6BK4 (ED500) The damper diode is a 6AU4GTA. An EY500 could be used a substitute.

This set is a delight to work on and much easier to gain access for service than many UK and Continental CTV sets made eight years after the CTC7 was introduced.

DFWB.

chipp1968 · 15th Oct 2007, 8:34 am

Looks nice.
How did you come by this set? I presume it must have been brought over from the States - and if so, how easy was that?

FERNSEH · 15th Oct 2007, 6:35 pm

Hi Chipp,
The set has been in my possession for five years. It was shipped over from America in a dismantled condition, the CRT, the cabinet and the chassis were sent over in separate boxes.
The set was easy to reassemble. Only the CRT is a bit tricky to remove and refit. I've kept quiet about the existence of this set, it's well known that I have the 1956 405 line colour set in my collection. The CTC7 is a much easier set to keep going, it's very reliable and NTSC colour signals are not all difficult to supply for the set. I have pre-recorded NTSC VHS tapes and the standards converter Samsung VCR.
The set was supplied over to me by Mr.Steve McVoy of the Early Television Foundation. www.earlytelevision.org/

My ultimate early colour TV ambition? The RCA CT100. The companies' first CTV to be offered to the buying public.

DFWB.

Dr-Watts · 16th Oct 2007, 4:16 pm

Any chance of a picture or two with a picture on the said telly ?

Dr. Dave

FERNSEH · 16th Oct 2007, 4:54 pm

Hi Dr. Dave,
Some good news. The line oscillator was sorted last night so now the line drive waveform is apparent at pin 1 (the control grid) of the 6DQ5 socket. The pin connections to the electrodes of this valve are quite different to those of most octal valves. Also, I've found a NOS EL509. I'll make up an octal to magnoval adaptor later today.

DFWB.

FERNSEH · 18th Oct 2007, 10:39 pm

I have disconnected the anode of the shunt stabiser tube (6BK4) and the result of the action is that the EHT voltage rose to a value where I had to disconnect 117 volt mains supply. The needle on the EHT meter swung way past the 25KV mark. Much to much for safety. So the problem is the shunt stabiliser. The cathode of the 6BK4 is connected to the 380 volt HT supply which is the fixed reference and the control grid is supplied from the boosted HT via a resistor divider network.

News flash: Thanks to the efforts of fellow a member I will soon have two 6DQ5 line output valves. The vintage-radio forum is a wonderful thing. Members help each other.

DFWB.

yagosaga · 19th Oct 2007, 3:19 pm

Hi FERNSEH,

I didn't know that there is such a large difference in power consumption between the 6CB5 and the 6DQ5. IMHO the 6CB5 can be replaced by an EL504 which would operate with 380V.

The test of your shunt regulator revealed that there might be a fault in the video amplifying unit. If the video output draws too much current, the shunt regulator will block the high voltage and you will see no brightness on the screen.

Do you have the schematics or should I search for it on my attic? I know that I have the schematics for the CTC-7. It is one of the most reliable early color tv sets in the U.S..

Kind regards,
Eckhard

FERNSEH · 19th Oct 2007, 4:47 pm

Hi Eckhard,
Thanks for your offer of information for the CTC7. I have schematics for for all versions of the CTC7, in fact I have the RCA FIELD SERVICE GUIDE which covers all the colour TV chassis from 1955 to 1966. Information for the CT100 in does not appear in the book but the 21CT55 employs a similar chassis, CTC2A.
The guide has information of the various tuner units and remote control systems employed in all the models.

Actually, the set has displayed a raster, but it did last long, the line oscillator failed again. I'll return to the set later today.

DFWB.

FERNSEH · 23rd Oct 2007, 8:57 pm

I've tamed the line oscillator and now I have a raster on the screen. I think that the EL509 is a much more efficient valve compared the 6BQ5. The EHT voltage is still too high so I am supplying the set with 105 volts to keep things under control.

The camera is still broken so I'll try to sort out my camera phone for pictures.

DFWB.

yagosaga · 24th Oct 2007, 7:22 pm

Do you have sound or any video content on the screen?

FERNSEH · 31st Oct 2007, 10:49 pm

Quote:

Originally Posted by yagosaga

Do you have sound or any video content on the screen?

I did. Now the focus voltage supply has failed so there no illumination on the screen. The focus rectifier diode is an 1V2, if that valve is faulty I could use a DY86 as replacement. Also, the reclaim diode (6AW4) has gone intermittent, it needs a tap to get it going. For a temporary replacement an EY500 or the EY88 can be used.

DFWB.

8th Oct 2007, 9:39 pm	#1
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	RCA CTC7 colour TV set On Saturday evening I promised myself and others that I would do something about the shop. Smarten the place up.The task in hand was to lay a new carpet. Anyway, I couldn't be bothered to do that so I decided to reposition the CRT in my 1958/9 RCA CTC7 colour TV set. The blue gun was not in a fully vertical position so it was out with the tube and refit it correctly. What a scary job! The CRT is an RCA all glass round type 21FBP22. My problem was refitting the CRT on to the mask, it did after moving the CRT about, carefully rocking it from side to side Finally it plopped into place. My set is called the "Abington" model number 21CD872. I cannot send any pictures right now. A picture of the set appears on Ed Reitans excellent color TV website: http://novia.net/~ereitan/Gallery/im...bington300.gif The set was kindly donated to my collection by Mr. Steve McVoy. DFWB. Last edited by FERNSEH; 8th Oct 2007 at 9:47 pm.

8th Oct 2007, 9:47 pm	#2
System A Pentode Join Date: Feb 2006 Location: County Durham, UK. Posts: 234	Re: RCA CTC7 colour TV set Hi David That set looks great! Does it have a metal shield that holds the degaussing coils in place, as in British sets? Will the set need much to get it going? Regards. Gary. Last edited by Mike Phelan; 7th Aug 2008 at 11:07 am. Reason: S&P

10th Oct 2007, 1:15 pm	#4
Dr-Watts Heptode Join Date: Dec 2006 Location: Milton Keynes, Buckinghamshire, UK. Posts: 696	Re: RCA CTC7 colour TV set Ah, early Colour (or Color) You just can't beat it I'd also love to see some pictures... pretty please Dr. Dave __________________ Do you have the scope to be a TV repair man

14th Oct 2007, 8:01 pm	#6
System A Pentode Join Date: Feb 2006 Location: County Durham, UK. Posts: 234	Re: RCA CTC7 colour TV set Hi Everyone! I spent a great morning at FERNSEH's shop yesterday, we put together his RCA Victor color TV. Here are some pictures of the set. Before I left FERNSEH's, we had hiss from the speaker but no line output. Maybe FERNSEH can update us. Regards, Gary. Attached Thumbnails

14th Oct 2007, 10:18 pm	#7
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: RCA CTC7 colour TV set Hi Gary, It seems that the line oscillator has stopped working and the lack of line drive to the 6DQ5 line output valve has caused that valve to fail. I'm OK for bits for the line oscillator as I have a spare chassis. The line oscillator is assembled on a small PCB and employs one valve, a 6CG7 twin triode. One triode is used in a blocking oscillator circuit and the other is the control valve. Apart from the types of valves employed in this receiver in the line output and EHT stage, the circuit will be familar to those interested in UK and continental hybrid colour TVs. All the valves except for the 1V2 focus diode have international octal bases. The EHT rectifier is a 3A3 which is similar to the GY501 and the EHT shunt stabiliser is a 6BK4 (ED500) The damper diode is a 6AU4GTA. An EY500 could be used a substitute. This set is a delight to work on and much easier to gain access for service than many UK and Continental CTV sets made eight years after the CTC7 was introduced. DFWB.

15th Oct 2007, 8:34 am	#8
chipp1968 Rest in Peace Join Date: Jul 2006 Location: Somerset, UK. Posts: 2,356	Re: RCA CTC7 colour TV set Looks nice. How did you come by this set? I presume it must have been brought over from the States - and if so, how easy was that? Last edited by Mike Phelan; 7th Aug 2008 at 11:10 am. Reason: S&P

15th Oct 2007, 6:35 pm	#9
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: RCA CTC7 colour TV set Hi Chipp, The set has been in my possession for five years. It was shipped over from America in a dismantled condition, the CRT, the cabinet and the chassis were sent over in separate boxes. The set was easy to reassemble. Only the CRT is a bit tricky to remove and refit. I've kept quiet about the existence of this set, it's well known that I have the 1956 405 line colour set in my collection. The CTC7 is a much easier set to keep going, it's very reliable and NTSC colour signals are not all difficult to supply for the set. I have pre-recorded NTSC VHS tapes and the standards converter Samsung VCR. The set was supplied over to me by Mr.Steve McVoy of the Early Television Foundation. www.earlytelevision.org/ My ultimate early colour TV ambition? The RCA CT100. The companies' first CTV to be offered to the buying public. DFWB.

16th Oct 2007, 4:16 pm	#10
Dr-Watts Heptode Join Date: Dec 2006 Location: Milton Keynes, Buckinghamshire, UK. Posts: 696	Re: RCA CTC7 colour TV set Any chance of a picture or two with a picture on the said telly ? Dr. Dave __________________ Do you have the scope to be a TV repair man

16th Oct 2007, 4:54 pm	#11
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: RCA CTC7 colour TV set Hi Dr. Dave, Some good news. The line oscillator was sorted last night so now the line drive waveform is apparent at pin 1 (the control grid) of the 6DQ5 socket. The pin connections to the electrodes of this valve are quite different to those of most octal valves. Also, I've found a NOS EL509. I'll make up an octal to magnoval adaptor later today. DFWB.

18th Oct 2007, 10:39 pm	#12
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: RCA CTC7 colour TV set I have disconnected the anode of the shunt stabiser tube (6BK4) and the result of the action is that the EHT voltage rose to a value where I had to disconnect 117 volt mains supply. The needle on the EHT meter swung way past the 25KV mark. Much to much for safety. So the problem is the shunt stabiliser. The cathode of the 6BK4 is connected to the 380 volt HT supply which is the fixed reference and the control grid is supplied from the boosted HT via a resistor divider network. News flash: Thanks to the efforts of fellow a member I will soon have two 6DQ5 line output valves. The vintage-radio forum is a wonderful thing. Members help each other. DFWB.

19th Oct 2007, 3:19 pm	#13
yagosaga Retired Dormant Member Join Date: Mar 2005 Location: Braunschweig, Germany Posts: 208	Re: RCA CTC7 colour TV set Hi FERNSEH, I didn't know that there is such a large difference in power consumption between the 6CB5 and the 6DQ5. IMHO the 6CB5 can be replaced by an EL504 which would operate with 380V. The test of your shunt regulator revealed that there might be a fault in the video amplifying unit. If the video output draws too much current, the shunt regulator will block the high voltage and you will see no brightness on the screen. Do you have the schematics or should I search for it on my attic? I know that I have the schematics for the CTC-7. It is one of the most reliable early color tv sets in the U.S.. Kind regards, Eckhard

19th Oct 2007, 4:47 pm	#14
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: RCA CTC7 colour TV set Hi Eckhard, Thanks for your offer of information for the CTC7. I have schematics for for all versions of the CTC7, in fact I have the RCA FIELD SERVICE GUIDE which covers all the colour TV chassis from 1955 to 1966. Information for the CT100 in does not appear in the book but the 21CT55 employs a similar chassis, CTC2A. The guide has information of the various tuner units and remote control systems employed in all the models. Actually, the set has displayed a raster, but it did last long, the line oscillator failed again. I'll return to the set later today. DFWB.

23rd Oct 2007, 8:57 pm	#15
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: RCA CTC7 colour TV set I've tamed the line oscillator and now I have a raster on the screen. I think that the EL509 is a much more efficient valve compared the 6BQ5. The EHT voltage is still too high so I am supplying the set with 105 volts to keep things under control. The camera is still broken so I'll try to sort out my camera phone for pictures. DFWB.

24th Oct 2007, 7:22 pm	#16
yagosaga Retired Dormant Member Join Date: Mar 2005 Location: Braunschweig, Germany Posts: 208	Re: RCA CTC7 colour TV set Do you have sound or any video content on the screen?