Motorola ts907 low hv

[Yamamaya42]

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.

[timmy]

No it couldn’t be protected.

[timmy]

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

[Yamamaya42]

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.

[timmy]

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.

[Yamamaya42]

Originally Posted by timmy

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.

[zeno]

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

[Yamamaya42]

Originally Posted by zeno

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

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

[Electronic M]

Originally Posted by Yamamaya42

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.

[old_tv_nut]

Originally Posted by Electronic M

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...

[damen]

1971 Sams index shows no bulletins.

[timmy]

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.

[Yamamaya42]

Originally Posted by timmy

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.

[timmy]

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.

[Yamamaya42]

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.