I have a 1968 RCA CTC 31 coor tv combo. I have the radio and phono working pretty good now. I want to check the tv part. The damper,horizontal output and high voltage rectifier are missing. The part of the tube chart is missing that shows those tubes. What are the tube #s.
Thanks,John.

The horoutput should be a 6je6 The damper a 6dw4 The hv rect a 3a3

If those tubes were pulled it is possible there is a high voltage or horizontal output transformer problem with that TV.

I found some tubes to try it out. There is a high voltage problem. The ho tube will redplate after a bit. I know that is caused from loss of drive but what causes the loss of drive?

bad horz osc tube or leaking coupling cap a the grid of the HOT. check the control grid of the HOT, should be about -50 to -60v (you will need to have the tube in place to check for this). If you have a scope you can check the PP of the drive, should be around 180-200 at the HOT control grid.

A shorted HO xfomer will also cherry the output... If it's cherrying almost instantly after warmup suspect no drive, if it takes 20-30 seconds or more suspect the HOT...


Tom

Add the focus rectifier and focus coil to the possible list of suspects. These were not among RCA's better sets.

I changed the horizontal osc tube. No change It does take up to a minute before the ho tube gets red. Is the HO xformer the flyback? Where is the focus coil located? The focus rectifier is the small tube on the side of the hv box.
John

check the grid voltage next, you need to determine if its a drive or a load problem. I checked the rca service manual says is should be around -44v.

Other than the red plating is it getting HV? raster?

focus coil is under the chassis under the fly cage. focus tube is mounted sideways on the fly cage.

could also be a bad HOT, try a 6LQ6 or 6JE6C (was recommended in later chassis runs).

Connect your volt meter to the SCREEN of the horizontal output tube, pin 1-7. You should be able to probe under the tube from the top of the chassis.

Connect the power and the voltage will start to drop as the tubes warm up.

The voltage should be around 135

If the voltage is much lower, say around 80 volts, there is no drive. If the voltage is higher, say 175 there is an overload in the output like a shorted flyback, bad yoke, shorted capacitor.

Dont let it red plate too long, even 20 seconds seriously degrades the tube.

There is no raster at all or the dot on the screen when turning it off. When checking the screen voltage do I use dc volts on the meter. Where do I check the grid voltage? If the flyback is bad where would I get one?
John

pin 2 will give you the control grid, look for -44v pin 7 is the screen. Use DC volts, the control grid will be neg, the screen will be positive.

as far as replacement flys, cross that bridge when you get there. At this point you need to diagnose the problem and determine where the fault is.

Use dc volts range.
Measuring the screen is an all in one test. The pulses on the grid may make your meter beep and go nuts.