ctc-5 hv problem - Page 2 - Videokarma.org TV - Video

holmesuser01 · #16 07-15-2006, 12:44 PM

Yes, THE SET COMES FIRST!!!

Obviously, I have no life.......

reeferman · #17 07-15-2006, 05:58 PM

Girlfriend's coming over, huh?

stromberg6 · #18 07-16-2006, 07:30 PM

Hi: If you have an original RCA schematic (maybe on Sams, also) for the CTC-5's, look closely at the CRT drawing. You will see that the "shroud" is also the filter capacitor for the high voltage supply, with a coating (auqadag?) inside and outside of the plastic base material. Deterioration of the plastic, particularly in the area of the mounting hardware, no doubt might cause arcing. I have a 5-N on which I just finished chassis work. I will now be faced with the HV problem. I plan to de-mount all CRT hardware, remove the shroud, and inspect for pinholes, etc., and will have HV putty, and corona dope on hand. I will post any info that might help. What a mess!!
Kevin G.

frenchy · #19 07-17-2006, 04:27 PM

I think this may have been my own fault, I think I was running it without the IV2 focus rectifier in the set, I had probably pulled it months ago testing out another set. Could this have damaged anything? Damn. The fuses on top are still ok, but the underchassis soldered-in 2 amp fuse was blown. Someone (the factory?) had put a piggyback fuse clip onto that fuse with a 3 amp slowblo in parallel so that circuit is still closed. Now I'm worrying this was put on by someone when it shouldn't have been. Anyway I pulled the chassis and retested all 5 tubes in the hv section and still zippo hv spark. I don't have any hv probes, only minimal testing equipment. If the IV2 was totally missing, what could that have fried, if anything? thanks

yagosaga · #20 07-17-2006, 04:35 PM

Quote:

Originally Posted by frenchy

I think this may have been my own fault, I think I was running it without the IV2 focus rectifier in the set, I had probably pulled it months ago testing out another set. Could this have damaged anything?

No. If this is the only fault, the set will operating again when you replace the 1V2.
But you reported some kind of arcing. This seems to be a more serious problem.

Eckhard

roundscreen · #21 07-17-2006, 08:42 PM

I did that with a 6bk4 once and that set put on a good light show and my ears were ringing the rest of the night. NOW I make sure I put the tube I am checking in the set I got the replacement from.
With the focus voltage missing and the set running for a period of time may have damaged the crt. I figured the damage starts when the guns are warmed up all the way. But I am not sure on that. Also the arc may have been inside the crt. Did you notice a blue glow from the neck of the crt?? The fuse sounds like someone put in a replacement. When they put in the 2 amp it more than likely opened a week later and then they put in the 3 amp slo blow.
Try this, See if you can get your hands on a high voltage probe. Put all the tubes back in and replace the fuse with the correct one. Disconnect the crt hv lead and socket.
Then check and see if you get hv. If you do, Then hook the crt back up and see if the hv goes down and look for arcing. If it does then you know it is the crt.
Please note that I am only guessing. I would need the set in front of me to know for sure what is going on. ALSO.. Please be careful with the hv, It is nasty stuff. I won't even get into the mistakes I have made with that.
ED

frenchy · #22 07-17-2006, 09:30 PM

Quote:

Originally Posted by roundscreen

Try this, See if you can get your hands on a high voltage probe. Put all the tubes back in and replace the fuse with the correct one. Disconnect the crt hv lead and socket.ED

That's what I've done today, the chassis is pulled and I am still getting no HV at the 3a3 hv terminal (grounded screwdriver) with all the tubes now in it and tested. I did not notice any popping or blue glow on the crt but then I was only looking at the screen when it happened, and didn't see anything there. Didn't see it when I had the back pulled either, all 3 guns were lit normally. It was pretty loud so I assumed it was an external pop and didn't see anything on the screen whatsoever either. Perhaps testing the crt with my crt tester would be in order. But I still have no hv period so I kind of assume the chassis problem is all I have and did not involve the crt. Would good readings on the crt test pretty much rule out damage? I forgot I do have a HV probe in the closet so I will see if I can remember how to hook it up and maybe make some measurements on the chassis. I do get a teeny tiny spark when I physically touch the screwdriver to the terminal, so there is SOME voltage on the 3a3 terminal at least, not nothing. Flyback looks great and I can't see where anything 'popped' anywhere else. Frenchy

reeferman · #23 07-17-2006, 11:56 PM

How was the weekend??

??

frenchy · #24 07-18-2006, 12:31 AM

: ) : ) : )

roundscreen · #25 07-18-2006, 07:57 AM

frenchy.
In a way that is good news. Remove the plate cap on the 6cb5 and see if you get a arc from the tube. Should be about a 1/4 inch long when it jumps to the screw driver. If you do, Put the cap back on the 6cb5 and Pull the cap on the 3a3 and see if you get a arc from the cap that comes out of the fly. That way you can figure the fly is working. Did you check the 6bk4 tube? It could be that is the problem. The caps or resistors in the hv regulator may be bad.
I am not sure what the crt tester would show if a crt is damaged by no focus voltage.
I would guess the crt went to air and the heaters would go out? That will give me something to do when I run into that again.
ED

frenchy · #26 07-18-2006, 04:58 PM

I get no spark whatsoever on either the the 6cb5 or the 3a3 cap tests. I tested the 6bk4 and it's a new one I swapped in after the hv failure.

roundscreen · #27 07-19-2006, 07:56 AM

Really, No arc at the 6cb5. This is interesting. Check for the b+ at the fuse at both ends, M4 on my sams 3/4 amp It Should be around 380-390 volts. Also please check the horz tube plate cap. With it disconnected from the tube, Check and see if you get a voltage reading. If b+ is on the fuse and horz plate cap try replaceing the horz out and damper tubes. They may check ok on the tester but when in circuit and under load they don't work.
Also do you have a variac? And what is the ac line voltage you run the set at?

ED

roundscreen · #28 07-19-2006, 08:55 AM

Me again
I just caught my self and yes I am a dumb ass.
Please recheck the 6cb5 for an arc. The plate cap must be on the tube to see the arc. {See picture} You do get one with the cap off but it is vary small. This is a b-w set but it should do the same thing on your set.
It was the only set I could get my hands on asap.
ED

frenchy · #29 07-19-2006, 11:08 AM

ok thanks will try these tests tonight.
Frenchy

yagosaga · #30 07-19-2006, 11:17 AM

Hi frenchy, read this thread
http://audiokarma.org/forums/showthread.php?t=30364
which is discussing similar problems. At first I would check whether the horizontal oscillator is working and whether there is a negative voltage at the grid of the horizontal output tube. What is the horizontal output current (measure at the cathode of the horizontal output tube or remove the horizontal fuse and measure the current across the fuse). Be sure that you are not in contact with the +b voltage.

Eckhard