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  #151  
Old 02-19-2017, 02:22 PM
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SwizzyMan SwizzyMan is offline
Restoring A CTC-4
 
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It actually turns out the smoking resistor is a 5k 10w coming off the color take off coil and feeding another 285v supply. I dont see any brown spots where burning has occurred on the resistor itself and I know a 10 watt dissipates a lot of heat. So it may just be dust on top of it burning off. But i recall never seeing any smoke until now coming from it. I checked tubes associated with it and none were shorted. I noticed that the resistor has a connection to G1 of the AGC amp tube. I had been adjusting the AGC in hope it may have given me a better picture, not sure if its set too high, but I dont think adjusting the AGC would cause this.
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  #152  
Old 02-19-2017, 06:29 PM
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Phil Nelson Phil Nelson is offline
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Quote:
Originally Posted by SwizzyMan View Post
I think Ive confirmed that the 3.58 oscillator is not running. I checked for waveforms on both sides of the crystal and I got nothing at all. Keep in mind I took this measurement with color control fully up, but not connected to the CRT so no HV or anything. I think I have a bad crystal.
In my CTC-4 article (http://antiqueradio.org/RCACTC-4ColorTelevision.htm ) you can read about various tests I performed around the color oscillator. It includes a procedure for bench testing your crystal, suggested by dtvmcdonald.

If you confirm that your crystal is a goner, shoot me a PM. I have a couple of spares lying around and I could donate one to the cause.

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  #153  
Old 02-19-2017, 07:46 PM
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SwizzyMan SwizzyMan is offline
Restoring A CTC-4
 
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Quote:
Originally Posted by Phil Nelson View Post
In my CTC-4 article (http://antiqueradio.org/RCACTC-4ColorTelevision.htm ) you can read about various tests I performed around the color oscillator. It includes a procedure for bench testing your crystal, suggested by dtvmcdonald.

If you confirm that your crystal is a goner, shoot me a PM. I have a couple of spares lying around and I could donate one to the cause.

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html
I'll Have to take you up on that offer! I tested for both a waveform and voltages on pin 6 of the 6AZ8 and I got absolutely nothing for both....Crystal is dead. I'll send you a PM.
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  #154  
Old 02-19-2017, 08:39 PM
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Quote:
Originally Posted by SwizzyMan View Post
It actually turns out the smoking resistor is a 5k 10w coming off the color take off coil and feeding another 285v supply. I dont see any brown spots where burning has occurred on the resistor itself and I know a 10 watt dissipates a lot of heat. So it may just be dust on top of it burning off. But i recall never seeing any smoke until now coming from it. I checked tubes associated with it and none were shorted. I noticed that the resistor has a connection to G1 of the AGC amp tube. I had been adjusting the AGC in hope it may have given me a better picture, not sure if its set too high, but I dont think adjusting the AGC would cause this.
That resistor is a red flag odds are there is a short or a mis-biased tube drawing too much current through it. Do voltage checks in the area around that resistor and on any tubes it feeds.
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  #155  
Old 02-20-2017, 11:13 AM
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It has to be an improperly biased tube causing the resistor to overheat. I checked almost everything downstream of it and found no shorted components. Will check voltages later.
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  #156  
Old 02-20-2017, 05:35 PM
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Restoring A CTC-4
 
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Was going to check voltages so I reconnected both resistors. After pulling the noise inverter 6u8 since it was connected to the resistor (thinking this may be the mis-biased tube.) to check for smoke, I got none. I put it back in the socket and still no smoke. The 5k resistor is no longer smoking and burning up. It is still warm to the touch but not burning hot. I now need to replace the 3.58 crystal. Phil Nelson was kind enough to donate a crystal to the cause so Im waiting on that getting here.
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  #157  
Old 02-20-2017, 06:42 PM
DaveWM DaveWM is offline
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shorted tubes can smoke resistors, and shorts can be intermittent.
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  #158  
Old 02-20-2017, 08:32 PM
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The underside of the CTC 4 is such a rats nest that it's easy for wires to short together. I had a similar issue on the CTC4 I'm restoring.
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  #159  
Old 02-20-2017, 08:35 PM
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I wasted a lot of time on my CTC-4 thinking Hickok tested meant something. Indeed failure to work as a chroma amp or intermittent shorts weren't always detected. Tubes are cheap enough, and those 6U8s and AZs are considered expendable under such heavy use. I just order NOS (usually Sylvania or GE) for all critical tubes for any color set so old and keep the old ones for emergency/if they work spares.
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  #160  
Old 02-21-2017, 05:36 PM
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Restoring A CTC-4
 
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I'll look around for any shorted wires, but my next order of business is to figure out how to get rid of the interference when the chroma signal comes in. It makes the picture unwatchable. I also have a bit of artifacts on the black and white signal now. I may just shotgun replace all resistors on the video board for good measure, but the chroma signal interference might be a different story.
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  #161  
Old 03-21-2017, 06:32 PM
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SwizzyMan SwizzyMan is offline
Restoring A CTC-4
 
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Got a new oscillator crystal courtesy of Phil Nelson (Thanks a bunch). I got it awhile ago in fact. I just haven't had time to get back to the set until this weekend. Hopefully replacing the bad crystal will clear up some problems. It's been almost a year working on this set and i've still got a ways to go.
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  #162  
Old 03-23-2017, 01:32 AM
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Tubejunke Tubejunke is offline
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Quote:
Originally Posted by jr_tech View Post
Perhaps there is some arcing that is causing the interference?
My thoughts exactly as I looked at those screen shots. Iím by no means a color TV expert, but I do have a Zenith roundie that had the slightest arching in the HV cage. It was hardly audible, but that was exactly what the picture looked like. Turned out that the HV rectifier socket was fried. Replaced that and no problems. In addition, I think that set needs degaussing. Most of us arenít lucky enough to have a real servicemanís degaussing ring, so I just use my Weller soldering gun in the same manner that you would use the ring.
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  #163  
Old 03-23-2017, 07:08 AM
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Quote:
Originally Posted by Tubejunke View Post
My thoughts exactly as I looked at those screen shots. Iím by no means a color TV expert, but I do have a Zenith roundie that had the slightest arching in the HV cage. It was hardly audible, but that was exactly what the picture looked like. Turned out that the HV rectifier socket was fried. Replaced that and no problems. In addition, I think that set needs degaussing. Most of us arenít lucky enough to have a real servicemanís degaussing ring, so I just use my Weller soldering gun in the same manner that you would use the ring.
I've got a real service degaussing coil and I've made spares....Allz you have to do to make one is find a decent sized 20" or bigger BPC set at the curb, steal it's degaussing coil, loop that 3 times around so it becomes a smaller coil ~12-14" in diameter, wrap it in electrical tape so it holds that form, and attach a cord.
...It will get hotter faster than a servicing coil, but one can get about a minute run time (plenty for most sets) out of it before it needs a cool. I made a thread on the process a while back.
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  #164  
Old 03-23-2017, 10:09 AM
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I think that this handy tip should have been made a sticky:

http://www.videokarma.org/showthread...hlight=degauss

jt
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  #165  
Old 03-23-2017, 11:24 AM
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Originally Posted by jr_tech View Post
I think that this handy tip should have been made a sticky:

http://www.videokarma.org/showthread...hlight=degauss

jt
I've made it into one.
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