1950 RCA 6T65 16" console - Page 2 - Videokarma.org TV - Video

*Bill Cahill* · #16 01-04-2008, 09:27 AM

You'd better check your new 630 volt capacitors. They can't handle the high pulse. The originals were 1,000 volt, and, it needs that in all critical areas. That is damper, horiz., and, vertical.
I suspect one of your new caps broke down.
Bill Cahill

Adam · #17 01-06-2008, 12:31 AM

Those caps even though they don't look it, actually are 1kv. I pulled that lin. coil out, and after looking at it more closely I could see that it was undone and then someone had tried to rewind it, I'm pretty sure there's problems with it. I swapped in the coil from my 730TV parts chassis. Then I checked all the horiz circuits to make sure they matched up with the schematic, after that wrong flyback and this coil I wanted to be sure no one messed anything else up. I didn't find anything, but I checked each resistor as I went, didn't find any that I think would be causing my problems, but am replacing any that were more than 10% off anyway.

When I tried it out, I very briefly got a vertical line down the center of the screen, then no picture at all, and an awful high pitched noise comming out of the speaker.

I checked the horiz osc, HO, damper, and HV rect. tubes again, all check out ok. I pulled the yoke, and after having the wrong fly in here I'm not sure if it's the right yoke either, resistance readings aren't too far off from where they should be, but there's that resistor in there in series with the vert. coils that doesn't appear on the schematic. Here's a pic.

*Bill Cahill* · #18 01-06-2008, 12:25 PM

What is the number on the yoke?
You have a failed horizontal section. Could be the yoke, but, it sounds more serious.
Bill

*Bill Cahill* · #19 01-06-2008, 12:26 PM

If someone put in a yoke that matched replacement flyback, then, it's the wrong one for the set.
Bill

Adam · #20 01-06-2008, 06:02 PM

The fuse between the +370v source and the lin coil blows whenever I plug the set in, and if I try it with the fuse bypassed I get what I described earlier (I didn't leave it on for more than a few seconds), and if I try it with the fuse blown, I get no HV as would be expected, but I also don't get that high pitched noise. I'm thinking something is drawing too much current and blowing that fuse, but I can't figure what. I can't find any shorts to ground, all tubes test good, new caps, new fly, the yoke is all I can think of that's left. Although I wouldn't think a mismatched yoke, unless there was actually something wrong with it would be doing this either. I couldn't find any numbers on the yoke. One cap I haven't replaced, but might try next is that 4.7pf cap hooked between the plate of the HO tube and the yoke, it's not shorted, but I don't have a capacitor tester on which I could check it any further. Becuse it keeps blowing that fuse, I don't really want to leave it on long enough to take any voltage readings, in case it damages my new flyback or other parts.

Tubejunke · #21 01-07-2008, 12:17 AM

It seems like my TC-127 had a wire that came from the power transformer and led to the fuse in the HV cage. I wonder if a shorted section in the power trans. could cause some of these symptoms. If memory serves me right the power transformer supplys a separate voltage to the damper tube. I want to say it was heater voltage but most of the dampers were 6.3 volt 6W4 or 6AX4 I think back then, same as the rest of the string minus the LV rectifier, so I may be off on this.

Also my TC-127 has a different chassis but a lot of that period RCA chassis were similar in setup. I am fairly certain this threads set would have the supply from the transformer. Just trying to help.

After nearly a year passing on my RCA restoration I have found enough needed tweaks to warrant chassis removal again. The sound is very low, sometimes the picture has a bit of vertical jitter/jumping and the vertical size shrinks just enough to make you want to try to adjust the size and lin. controls which are cranked all the way. I'm thinking resistor issues on nearly all of this and a possible cold solder joint from the recap. Actually truth be known there are still two or three of the fake mica caps that are actually paper left in my set. They get overlooked a LOT as caps that have a low failure rate but are in fact unreliable paper caps with the same color dot code and look as the longer life micas.

In my stupidity I left a few fake mica's in my set knowing what I just told you all. Still in all I was more than pleased with the results I got with this set. These sets offer a SUPER crisp picture I think....

Adam · #22 01-07-2008, 12:32 AM

The power trans does have a seperate winding just for the filament voltage on the damper tube (6W4)

*Bill Cahill* · #23 01-07-2008, 12:20 PM

Yes, and that winding is not grounded. It is insulated at 2500 volts because RCA put the cathode on the filament to prevent arcing.Arcing was a big problem with those tubes. If the winding is leaking to the chassis it would cause a short in B+, which would blow that fuse, and make alot of other stuff un happy until it does. Bypassing fuse is very bad on the flyback. Not a good thing. You MUST stay with the original value .25A,250 slo blo fuse. Clips can be had to adapt the new fuse to the old pig tail fuse.

Looks like you are past the guess it could be this part point. Start tracing, do resistance measurements in circuits, etc.. You obviously have a short.
Bill Cahill Get a capacitor tester for those new caps you installed. My guess still would be that one, or, more of them has failed. It only takes one to cause a short.
Try unplugging the yoke, and, put a jumper wire over the two pins that connect the 5U4 the the rest of the set.. Power it up, with a proper fuse, and, see if it still blows. If so, the short is somewhere else.. Is it your vertical, or your horiz. that failed? If it was truly the entire horiz.then, you shouldn't get a vertical line..It has to work at least a small amount for the flyback to work.. Is flyback wired properly? Did you make any mistakes in your wiring? The cloth covered wires, and, I warn you, they have damper pulse on them, that go from the damper filament to the terminal strip below that has thw cloth wires from power transformer, and, those wires, tend to fail, and, rot.
Also, I doubt your problem is that coupling capacitor. That's a special capacitor rated at a very high voltage, by the way. I believe it's rated at something like 2500 volts.
There is an extremely high pulse on the plate of the horizontal output tube.
Bill Cahill

wa2ise · #24 01-07-2008, 05:07 PM

Quote:

Originally Posted by Adam

I pulled the yoke, and after having the wrong fly in here I'm not sure if it's the right yoke either, resistance readings aren't too far off from where they should be, but there's that resistor in there in series with the vert. coils that doesn't appear on the schematic. Here's a pic.

That's not a resistor, it's a small value cap. Probably something like 47pF.

*zenithfan1* · #25 01-12-2008, 10:17 PM

Nice set!! I am into mostly early color but I can't help but love the B/Ws. I am trying to find some '40s sets for my collection.
Mark

Adam · #26 01-12-2008, 10:32 PM

Thanks, nice Zenith roundie, I have 2 early color sets a 1963 Philco combo, and a CTC-10 w/ remote, I have yet to start working on the 10. Southern CA seems to be completely lacking of Zenith roundies, in 6 years of collecting sets down here I haven't seen a single one.

That is a 47pf cap in the front of the yoke, but there's a resistor over on the left side, according to my schematic the yoke should have 2 caps in it and no resistors, I'll take a good look at it and see how it's wired then post up a schematic of it vs. the one that's supposed to be in there.

Any resistance tests I make show nothing wrong with the set. I ordered .02mfd 1.6kv replacements for those .018mfd 1kv caps, (I figured the .002 mfd difference wouldn't cause any problems) I guess something could have happened to them when I turned it on with the wrong fly in there.

Adam · #27 01-20-2008, 11:34 AM

I swapped those caps, but that yoke is definetly not what should be in there according to the schematic I have, so I think I'm going to wait to get a yoke before I try this set again.
Now I'm on to figure out what happened to the HV in my '54 Westinghouse...

***Eric H*** · #28 01-20-2008, 01:10 PM

I gotta say after seeing all the problems that Adam and Bill have had with this particular model chassis I hope I never have to fix one!

7"estatdef · #29 01-22-2008, 03:13 PM

On my KCS-47A I haven't had much trouble getting it going. Just the normal stuff like no sync, horz freq stablbilly, and HV filter cap bad. Haven't worked on it since holidays it got moved to put the xmas tree up.

Terry

Adam · #30 10-12-2008, 04:39 AM

Made some progress on this set tonight. I put in the new correct yoke, and still had the same problems as before, but noted that the 5U4 was glowing excessively bright as well as the damper tube. It turns out the filament winding for the damper tube was arcing inside the power transformer, either to the 5U4 filament winding, or main secondary windings. I had dismissed the idea of a short in the power transformer being a problem when I tested it for shorts and found nothing, but even though it's not actually shorted it appears something is arcing in there when it's working. I powered the damper tube filament off a separate transformer, and pulled up this blank raster. I still have no picture or sound, but at least I got HV.

This set sure needed a lot of new parts. The power trans must have been the original cause of this set's problems, but it burnt out the lin coil, and caused someone long ago to replace both the yoke and the fly (with the wrong ones!) and then loose the hv filter cap. At least the 16GP4 is still good (the brightness isn't up all the way in the pic)