The circuit breaker as shown on the SAMS is starting to bug me A LOT.
It has to be an error.
With the secondary rated at 143v @ .58a, there is absolutely no way for it to be protected by a 4.5a circuit breaker, the transformer would self destruct long before the 4.5 breaker tripped.

I have checked the RCA CTC 10/11/15 schematics, which have basically the same type of power supplies, and they have 2.1a breakers.
https://www.ebay.com/itm/393284894216
which makes much more sense.
The SAMS listing of 4.5a has to be an error, IMOH.

No it couldn’t be protected.

Is it at all remotely possible that the diodes or one of the diodes could be compromised in some way.

If that were the case, you would likely see more drastic effects like excessive AC ripple at L54, if the diodes were not working well, or overloaded, the listed 1.5 ptp would be higher.

Double check the transformer 148vac befor diodes. I guess it’s time to start cutting wires to the specific circuits the 275 145 190 and each one cut hopefully the problem shows itself.

That will achieve very little, if anything at all.

The moment you start to deny power to areas, sooner or later you will hit something critical, and cause horizontal sweep to shut down, and thus no HV, or vertical and raster, and w/o that, the power will spike.
There is just no way around it, you need a better DVM to measure current draw to see if you do indeed have too much draw.

On breaker we used Mallorys. They had a carry & break rating.
The hoz outs alone are good for 240ma.
You can try pulling all the low level tubes & leaving in the hoz AFC, H osc,
2 hoz outs, damper, HV rect and HV reg. BTW I looked, can someone
post the PS schematic ?
Also does anyone look at an OLD Sams index & see if there are any
PCB's on this set ? I have a 2001 & for some reason none
of the TS chassii are listed.

Zeno:smoke:

this is the only one I know of.
https://www.earlytelevision.org/pdf/...sams_739-3.pdf
seems all point 2 point.

The only pre-WID rectangular-color tube motos I have seen are hand wired and looked like what you'd get if a Zenith TV and a car radio had an illegitimate kid.

I think moto kept their color TVs hand wired till WID came along.

:lmao:

1971 Sams index shows no bulletins.

Ok got an update the 6gk6 pin 1 150 ohm resistor to ground burned up changed the resistor and that one started getting real hot so I pulled the tube and put the old one tube in and it didn’t get hot again but at the same time the old tube shows very little emission on the tester so this resistor may not be getting hot because the tube is bearly conducting. So I have to wonder why this is happening with a new tube either the tube is defective or something else is being affected in the audio circuit. And with the old tube in all the voltages came back to normal so this was the problem area. So what possibly could cause this when the tube conducts.

That's almost always caused by excessive grid leakage, IE g1 being pulled WAY too high ( off 0v) forcing the tube full on, C55/C56 bad / leaky? If there were at one point, the output T5 may be damaged, and needs to be tested, but it says 0v at pin 2 of the 6gk6, if you do not see this when it's up and running, C55/C56 are leaking the 90v from the det.

and do check the output x-fomer.

The audio trans checks good so are you saying the tube is good and it my be a cap ? Because the tube gets extremely hot in a short amount of time like it’s full on.

Check for voltage at pin 2 of the 6gk6, or the volume cont, ( same circuit ), if not 0v or close to, then you need to find why it's not.

most likely bad caps.

way too much info on the subject! :D

http://www.geofex.com/ampdbug/coupling.htm

Pin 2 is showing 55mv and the tube is slightly red plating.

And it's quite normal for miniature output tubes to get hot enough to burn your skin off, but smoking the cathode resistor is NOT normal.

No it’s not normal but it was nice to see the voltages normal now I have to find the cap culprit.

Here is an example of a breaker with ratings
IIRC the hold is max amps that will not give accidental trips.
The break is for instant trips.
https://www.tedss.com/CBT400/

Thermistor seems just to prevent high cold set inrush current.
Should go to 0 ohms hot. You can jump it out to test.
When its cold you can put an ohm meter on it & heat it with a heat gun
etc & watch it drop in value.
BTW most thermistors that fall apart can be soldered back together to get you by.
Now if you leave out the 6GK6 you can work on everything else.

Zeno:smoke:

https://frank.pocnet.net/sheets/049/6/6GK6.pdf
55mv (0.056 V) Is infinitesimal, not enough to be causing the problem, you have something else going on here.

check check and re-check

Primary of t5 (930 ohms)
C55/C56/C57/C58 ( All but c57 rated 1kv or higher)
6gk6 tubes, they may be bad even if tester says they are OK.
Make sure the output transformer is good and all caps are of good quality, you could be having a problem with parasitic oscillation, (high freq) that is overloading the output.

One thing to try is to ground the center pin ( wiper ) of the volume pot, this will force the grid to 0v, if you STILL red plate, then you know the problem is something else.

And I believe it’s the tube I have the chassis on the bench and tube in the resistor gets hot I pull the plug then plug back in and resistor stays cool it seems to be random and those 2 caps they only matter if the plug is in to complete the volume circuit so that really don’t leave much but the tube or a .005 pin 8 cap because it gets hot all plugged in and complete or on the bench.

1.4 ohms secondary primary .933 ohms comes up as k ohms. That’s good.

Do try what I mentioned, tie the center of the volume control to gnd and see if it stops getting hot.

The volume control is not plugged in this has become a random thing one moment the resistor and tube gets hot then it don’t even not plugged into the volume control so it don’t matter at this point if the chassis is in or out. Now it’s looking like a defective tube or as the schematic shows a .005 to ground with a 145v source on the other end but the sams don’t show that it has 2 .005 caps not one.

W/o that volume plugged in, there is nothing to keep that grid pulled low, and it will float high, causing the tube to bias on.

If it keeps acting up, what I would do is.

Replace BOTH c54/c56 with something like 667-ECW-H20103HV & c55 with something like 667-ECW-H8102RHV , and so on.
There is a tie to boost voltage via r82, but since there is no diode on this line, this means there is a strong horz pulse there, c54 is there to filter that, c56 is there as bypass and let only audio to the output stage, if ANY of these caps are faulty, DC and/or horz pulses can be passed on to the output.

What does the x z and w represent. Can a ceramic disc intermittently leak or short.

667-ECW-H20103HV & 667-ECW-H8102RHV are mouser part numbers
I did not wanna paste huge links here
tiny links
https://tinyurl.com/2p8apn29
https://tinyurl.com/yvbjsc9k
ceramic discs normally dont give problems, BUT, it does not mean the never do.

paper caps. ALWAYS BAD.

Vintage film caps and Mica, most of the time, don't act up, but I HAVE seen them cooked to death and bad before.
https://imgur.com/veMo2go
these are from my CTC-16XL and were causing color problems.

in other words, you must treat all old caps on a case by case basis by diagnosis ASIDE from the paper and electrolytic, which you will always assume to be bad.

My dvm has a capacitor mode to check them and it’s a great thing to have but even though they check good in circuit and under load I know is a different story. It can check uf and nf.

correct, a DVM cant test for leakage.

Hey thank you for all the help you have been offering me I do appreciate it.

=^-^=

sneaking onto here helps with the boredom @ work!

" OH GREAT, THANKS! 25 MORE PRODUCTION BOARDS FAILED, YOU WANT THEM DEBUGGED BY WHEN!?!?" :scratch2::yikes:

Lol ��

This 150 ohm resistor if it burned up down to 95 ohms would this alone cause the tube to go full on ? If zero ohms at pin 2 will cause the tube to go full on then how can the tube go full on if there is any voltage getting past c55 and c56 that would have voltage at pin 2 so I would think if it’s not zero and there’s voltage present then the tube wouldn’t be full on. I checked the volume pot it measures 2.4meg wiper varies ok. So just changing the burned resistor should this fix this at all.

The 150 ohm cathode resistor is for limiting current, even if it was not there, it would not overload the tube.

The only thing that could is too much positive voltage on pin 2.
And as stated before, W/O the volume control plugged in, there is nothing to stop the grid from creeping up and turning the tube on, this is a design flaw.

Ok well maybe at some time of the history of this set maybe someone had unplugged the harness that carry’s the volume control and it burned the resistor so I’m still not sure about the tube. That’s the only one wire on the volume control that goes to pin 2 so with all hooked up the tube shouldn’t run away but if it does then I don’t know from there. I changed all those caps you mentioned and the booster leg with the 1.5 meg resistor is good. Or maybe between the plug connector maybe a bad mate within the plug itself.

You could always hook your DVM to the center post of the volume control ( wiper ) with the set in operation, and move the control through it's entire range, you should not see a voltage much higher than 0v, a few millivolts are not enough to cause a problem, but 2-5v or more, PROBLEM! :O

I checked continuity of the wires on the volume control as well as the changing ohms when I rotate the knob it all looks great.