ctc16 roundie combo

[freakaftr8]

Had this happen on one of my CTC17's. The picture would bloom to a purpleish hue and then would bloom to the point of raster fade out. I noticed the 6GU7 filiments going out at this point. Reflowed solder on the chroma board grounds and viola. Problem solved. Board flexing seemes to take it's toll on those grounds.

Originally Posted by old_coot88

Hey reflow solder on the two ground stakes on the far right end of the chroma board. These grounds open and kill the 6GU7 heaters. Very common ailment of the CTC-15, 16, 17 and 25 chassis. It can cause a 'cascade' of events: 6GU7 plates go 'waay positive, driving CRT grids positive (since they're direct coupled), causing CRT beam current to avalanche, which can kill the 3A3 and eventually fry the flyback if left to run unchecked. Bill(oc)

[DaveWM]

Great info to have thanks OC, I have a 17 on the back burner, I will check those out when time.

[miniman82]

I don't know if it's the solder they originally used or just the passage of time, but bad joints are very common. The CTC-7 I just picked up had the convergence board only hanging on by 1 ground point, which was itself loose. I always reflow joints that look suspect with fresh stuff, just to make sure I have good connections.

[holmesuser01]

Originally Posted by miniman82

I don't know if it's the solder they originally used or just the passage of time, but bad joints are very common. The CTC-7 I just picked up had the convergence board only hanging on by 1 ground point, which was itself loose. I always reflow joints that look suspect with fresh stuff, just to make sure I have good connections.

My CTC-10C also had ground stake problems at the PCB's. I could bump the chassis and cause the raster to go black for a moment. Poked the PCB with a pencil eraser, and found the problem. I've never had this problem again, at least on this set.

[old_coot88]

Originally Posted by freakaftr8

...Reflowed solder on the chroma board grounds and viola. Problem solved. Board flexing seemes to take it's toll on those grounds.

Yep. Didn't take more than a coupla cycles of pulling/reinserting tubes to crack those joints originally. Reflowing with a heftier mass of solder generally solved the problem.