1950 RCA 6T65 16" console

[Dan Starnes]

Keep up the great work!
Dan

[Adam]

Thanks. Messing with the tuner does nothing, no static out of the speaker, or on the screen when I change the channels. Turning the volume control does produce some static. With both no picture or sound and the tuner doing nothing, I'm thinking the problem has to lie in the IF sections common to both. In this set the sound comes off after the 2nd IF tube, so that narrows it down a bit. It could be the local oscillator coils in the tuner need adjustment like they did on my 721ts, but with the tuner having no effect at all on the picture, I'm thinking there's something else wrong here. I'll pull the chassis later and check it out after I see if I can get ahold of a new power transformer. With 4 video IF sections this set must have been quite a performer in it's day.

[Bill Cahill]

There are two common problems that happen on this set of chassis' KCS 47.
1 Open resistor on 2nd video I F
2 Bad tuner.
If while changing channel selector you hear a slight scraping sound , and, or, it's acting unusually tight, the switches are badly worn, and, bent. Best to keep looking for another chassis with a better tuner.
Have you tested your tubes?
Sound does get its' take off from 2nd video I F, but, tuner uses two seperate frequencies. One carrier is for the picture, and, other is for the sound carrier.
Bill Cahill

[Bill Cahill]

Originally Posted by Adam

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)

You can easily remedy this problem of arcing.
Remove the jumper wire from the cathode of the damper to the filament pin. This removes the boost from filament winding. Then, replace the 6W4 with a 6AX4, which should stop the tendency of the tube to arc internally.
The 6W4 had a tendency to arc, so several companies, including RCA put a special hv isolation winding on power transformer, and, tied the cathode to the filament. My 6AX4 doesn't arc, and, it works fine.
You are on your way....
Yes, this seems to be a troublesome chassis.
Bill Cahill

[Tubejunke]

If it makes anyone feel any better I had exellent results in restoring my RCA which again is a TC-127, but should be basically the same chassis. Really I was surprised at the good luck that I had even after frying the power transformer by being dumb enough to throw 110V.A.C. to it after only a few hours of the trick with the 100w light bulb. I lucked out on a replacement transformer to the tune of $40.

I also hace an 8T-243 which also is the same chassis design and it had power supply issues as well, although I didn't lose the transformer. Adam, make sure that when you power this thing up that the transformer stays cool. If it is getting hot than do not plug it in until you find out for sure what is going on. That bright glowing 5U4 worries me.

Also, I remember that the negative sides of the filter capacitors in the power supply do not go to chassis ground. I almost made the mistake of assuming that they would and I would be scared to think of what would have come of it had I made this mistake. It would be an easy one to make. It was a good lesson learned (the easy way) for me to realize that I need to be 100% aware of where each component connects before I assume ANYTHING.

You may want to check this yourself....

[Bill Cahill]

Well, actually, no. The chassis in the 6T65, etc., is nothing like the others at all..
It was a more cheaply made chassis, and, B- WAS on the chassis.
No similarity, whatsoever.
Bill Cahill

[kbmuri]

Rule of thumb:

If the electrolytic cap cans are covered in cardboard, they're very probably not at chassis ground. If they're bare metal, they probably are at chassis ground. Obvious reason, risk of shock touching the "hot"-neg cans if not insulated with cardboard.

Maybe not universal, but true in every case I've run across.

Adam's photo in post#1 shows bare metal cans. So reasonably assume their B- is at chassis ground.

[Bill Cahill]

Just a note of information:
RCA's KCS 47, 49 series of tv's had all B- on Chassis.
Some of the early sets don't have cardboard on one of the main filters, but, B- is above the chassis.
Bill Cahill