Back to the VT-71H

[Chris K]

Originally Posted by bandersen

It is not present. The TS-4H does not use that section of the ballast.

Seems like something is dragging the supply voltage down. Probably why the ballast is hot.

In the ballast I built pins 6 and 8 are unused. The CL-90 is not on pin 6. I put it on pin 5.

[Chris K]

Originally Posted by timmy

Why would it be shown on the ballast if it’s not in the circuit? I am putting a ballast together with resistors to rule out any trouble with the one in there now. So only 8-6 is not used?

Hi Tim. Take the cage off the ballast I built and check it before you go through the trouble of making a new one. I don’t care if it’s torn up getting to the inside. Do what u need to do!

[timmy]

Well I went over the power supply cap wiring and it looks good it’s correct however the b+ is low 111v and the b++ is also low 276v some of these sets are 150 and 300 others list 150 and 250 this ts-4h lists 150 and 300v so this is why I’m thinking of putting a ballast together.

[Chris K]

Originally Posted by timmy

Well I went over the power supply cap wiring and it looks good it’s correct however the b+ is low 111v and the b++ is also low 276v some of these sets are 150 and 300 others list 150 and 250 this ts-4h lists 150 and 300v so this is why I’m thinking of putting a ballast together.

Whatever you decide to do. It’s up to you!

[Yamamaya42]

From what I can see, there is no reason that Bob's design for the ballast should not be working, IF, it was made correctly, and there is no fault elsewhere.

You should take a very close look at it and how it was built.

This is my understanding of how it works.
CL-90 thermistor (120 cold 3 hot) = inrush dampening.
1n5408 x2 = dc for filament strings, lowers voltage & current.
39 ohms 7w & 18 ohms 3w = load balance for the 2 filament strings.
22-33 ohms 5w = shock dampening for voltage doubler capacitors / diodes.
200 ohms 5w = part of voltage divider for lower bias area.

If you go over it very carefully, and find no mistake, like something wired wrong, or damaged diode, or whatever, if it is getting too hot, then what part of it is getting hot?
What ever individual component that seems to be getting much hotter than any others, should be some clue of the problem.

[timmy]

Unfortunately I’m having another brain fart the ballast looking at the bottom of the socket under chassis number 1 starts clockwise and counterclockwise if looking down at the socket on top of chassis would that be correct? I know the key marks 1 and 8.

[Chris K]

Originally Posted by timmy

Unfortunately I’m having another brain fart the ballast looking at the bottom of the socket under chassis number 1 starts clockwise and counterclockwise if looking down at the socket on top of chassis would that be correct? I know the key marks 1 and 8.

That's the way I wired the ballast...with the socket being read like a tube socket, numbers read clockwise from the bottom, counterclockwise from the top

[bandersen]

Originally Posted by timmy

Why would it be shown on the ballast if it’s not in the circuit? I am putting a ballast together with resistors to rule out any trouble with the one in there now. So only 8-6 is not used?

It's shown because they all use the same ballast. They just didn't need that section in the TS-4H

[timmy]

Originally Posted by Chris K

That's the way I wired the ballast...with the socket being read like a tube socket, numbers read clockwise from the bottom, counterclockwise from the top

I just wired one up and it don’t work I used the same resistors that I used in my other sets and they work it’s kind of puzzling

[bandersen]

Originally Posted by Yamamaya42

I see what's going on here, it states in the table of contents that this moto service manual only covers up to TS-4D, therefore changes made on TS-4H won't be in there.

You will have to be very careful going forward with this.

Sure, it does. TH-4H through TS-4J late are in a pocket.



Here's the TS-4H schematic: https://www.earlytelevision.org/imag..._vt71_ts4h.jpg

[bandersen]

Originally Posted by timmy

I just wired one up and it don’t work I used the same resistors that I used in my other sets and they work it’s kind of puzzling

Did you wire it up so that the AC is going to pin 5 and not 6?

[timmy]

So I wired clockwise looking at the plug pins 200 ohm 4-3 50 ohm 1-5 150 ohm 6-7 150ohm 6-2

[bandersen]

Well there's your problem. That's the wrong ballast for this revision. Switch pins 6 and 5

[bandersen]

Also 150 ohms is a bit too much. 120 would be better

[Chris K]

This is what I did as per Bob’s instructions. These are his photos. The only change I made was switching the CL-90 lead from pin 6 to pin 5.