WCF720
09-20-2011, 08:46 AM
Greetings all, I wanted to pose a few questions to my fellow CTC-11 collectors. In working on the 11’s restoration, I have encountered a few dilemmas…
• I cannot find a value for the thermistor on the primary of the power supply, except that it is 79 ohms cold. What are people doing to replace these? Mine was bypassed by twisting its leads together. I did find a 75ohm 4-amp part I purchased thru DigiKey.
• The 3-amp circuit breaker was mechanically broken, where can these be obtained?
• My 3A3 was replaced with a 3A3C which was shorted. I tested the flyback and it revealed 9 rings so I “assume” it survived. The plate cap to the 3A3 is burned and has green corrosion plus signs of internal arcing. Replace it or use a Dremel tool to grind the corrosion off and use the existing cap again?
• Any reason I should not incorporate a ground buss for the circuit board ground pads on each board? My video IF board had every ground lug broken loose and a nice ‘cobble-job’ to create a ground using a spring! Perhaps a wire soldered to a chassis ground somewhere close that connects the grounds? Good idea or bad?
Restoration update. So far; shorted 3A3C, open filament on the damper (6AU4 substituted with a 6AX4), shorted video IF (6GM6), nearly zero emission on the sound IF (6EW6), weak focus rectifier (1V2), a 6GH8 with zero emission (go figure), and a shorted X-Y demodulator (12AZ7). All of the OEM 6CG7’s were in run down condition with poor emission; all have now been replaced. In checking resistors, I was rather impressed most I could check were within tolerance. Two 22m 2-watt resistors (which DigiKey did not have) in the high voltage cage were off by about 40%, the three 100 ohm resistors on the convergence board were way high, a 150 ohm coupler in the video IF was about 30% high, and one bad 470 on the sound board. I suspect the set was run into the late 70’s, one FP electrolytic appears to have a date stamp of 1976 (I think).
Are the board grounds a chronic problem with the RCA’s? It appears that most of the tubes that generated any kind of heat crystallized the solder on the socket lugs too. The Brookfield cabinet is buffed out, and the brown-black gunk on the CTR is cleaned off too, that crap is nasty!
• I cannot find a value for the thermistor on the primary of the power supply, except that it is 79 ohms cold. What are people doing to replace these? Mine was bypassed by twisting its leads together. I did find a 75ohm 4-amp part I purchased thru DigiKey.
• The 3-amp circuit breaker was mechanically broken, where can these be obtained?
• My 3A3 was replaced with a 3A3C which was shorted. I tested the flyback and it revealed 9 rings so I “assume” it survived. The plate cap to the 3A3 is burned and has green corrosion plus signs of internal arcing. Replace it or use a Dremel tool to grind the corrosion off and use the existing cap again?
• Any reason I should not incorporate a ground buss for the circuit board ground pads on each board? My video IF board had every ground lug broken loose and a nice ‘cobble-job’ to create a ground using a spring! Perhaps a wire soldered to a chassis ground somewhere close that connects the grounds? Good idea or bad?
Restoration update. So far; shorted 3A3C, open filament on the damper (6AU4 substituted with a 6AX4), shorted video IF (6GM6), nearly zero emission on the sound IF (6EW6), weak focus rectifier (1V2), a 6GH8 with zero emission (go figure), and a shorted X-Y demodulator (12AZ7). All of the OEM 6CG7’s were in run down condition with poor emission; all have now been replaced. In checking resistors, I was rather impressed most I could check were within tolerance. Two 22m 2-watt resistors (which DigiKey did not have) in the high voltage cage were off by about 40%, the three 100 ohm resistors on the convergence board were way high, a 150 ohm coupler in the video IF was about 30% high, and one bad 470 on the sound board. I suspect the set was run into the late 70’s, one FP electrolytic appears to have a date stamp of 1976 (I think).
Are the board grounds a chronic problem with the RCA’s? It appears that most of the tubes that generated any kind of heat crystallized the solder on the socket lugs too. The Brookfield cabinet is buffed out, and the brown-black gunk on the CTR is cleaned off too, that crap is nasty!