Motorola ts907 low hv

[timmy]

Ok upon turning on voltage starts high of course then it steadily drops the 275v dropped 226v then momentarily went up 260v ok well again I’ll leave the voltages alone but now back to the video problem with the test caps in place I removed the ground for a moment and made really no difference just alittle snow dots that’s it. Batteries are dead in the subber they don’t last.

[timmy]

The antenna put in at v1 pin 2 but v1 pin 7 it’s a better picture v2 pin 2 about the same and pin 7 no video. I put the new focus coil in and it along with L42 is still getting really hot if I leave it on long enough it’s got to burn up L42 and the focus coil. I can’t help but think these 2 problems video and overheating L42 and focus coil are related.

[Yamamaya42]

Not exactly sure what you are doing here, "The antenna put in at v1 pin 2 but v1 pin 7 it’s a better picture v2 pin 2 about the same and pin 7 no video."

this is a bit hard to follow :O

[timmy]

Originally Posted by Yamamaya42

Not exactly sure what you are doing here, "The antenna put in at v1 pin 2 but v1 pin 7 it’s a better picture v2 pin 2 about the same and pin 7 no video."

this is a bit hard to follow :O

The better pic is v2 pin 7 and the others I do get some video it’s better if v1 tube is left in.

[timmy]

At this point I feel like I’m chasing something that I may not find because with L42 overheating and focus coil overheating I probably think I should put my time into finding out why these are overheating.

[timmy]

The 770v tests 780v the 640v tests 620v the crt anode brightness down 24kv I don’t even know if L42 is supposed to have 780v on it I’m alittle lost not knowing the proper voltages that should be there it’s obvious there is to much voltage there.

[Yamamaya42]

For that you will have to do as SB suggested.
======
Also for L42 getting hot, you know each coil & Cap are a tuned circuit, If there is something
wrong, it may be peaking at a poor point and creating too much power.

All I can think of right now would be to check focus voltage as best you can.
Since the flyback was removed, it may be a good idea to try and see as best you
can that the pins that go where you think they go have the right resistance on
them as best as you can determine.

Take a picture, several pictures, of the flyback wiring, then disconnect all the wires,
measure the resistance of all the pins as you see them using both schematics, and
try and determine if it's wired correctly. You may also want to check resistance
from one isolated winding to another, This confirms no short between windings
and that they are wired correctly inside the transformer.... Since you have 2
Flyback transformers, you can compare between the two.....

My thinking is that since that flyback has pins that are tied to components and then
back to other parts of the flyback, that if a wire is not connected right, then voltage
may be fed to, or from one section out of phase, and causing problems, possibly
even heat on L42.
====
Mainly pins 1 & 5.
Others may be involved, but 1&5 hook directly to L42 & the focus coil, and must be unhooked to get a good reading, which SAMS says is .45 ohms, I think.

[timmy]

Before I put the flyback back in the resistances we’re good and the focus voltage measured perfect. And the other flyback I determined was bad I couldn’t get the hv right that why I put the old one back in and before taking the old fly out I drew a picture of the wires and colors where they came from and that’s how I put it back. So if it’s determined to be right and resistance is good then I’m still looking for a problem.

[Yamamaya42]

never hurts to double check stuff, cause there has to be a fault local to the FBT & focus area someplace.

[timmy]

Originally Posted by Yamamaya42

never hurts to double check stuff, cause there has to be a fault local to the FBT & focus area someplace.

I traced all the wires before and they all were good so next I’ll pull the chassis and disconnect all wires and check resistance on the flyback. I just checked the new flyback I have and all the coil taps check perfect but the donut checks at 470 ohms but the paper with the resistances it came with says it should be 640 ohms is that close enough.

[Yamamaya42]

Originally Posted by timmy

I traced all the wires before and they all were good so next I’ll pull the chassis and disconnect all wires and check resistance on the flyback. I just checked the new flyback I have and all the coil taps check perfect but the donut checks at 470 ohms but the paper with the resistances it came with says it should be 640 ohms is that close enough.

too low, pin 12 to the cap of 3AT2 should be at least 600, so it has shorted turns, or is the wrong part.

[timmy]

Originally Posted by Yamamaya42

too low, pin 12 to the cap of 3AT2 should be at least 600, so it has shorted turns, or is the wrong part.

Ok well that explains why I couldn’t get the hv right. I checked the donut on the original fly it’s 582 ohms so that’s good then I hope. I’ll be tracing wires again and checking resistances on the old flyback.

[timmy]

Donut 585ohms
1-2 .9
7-2 .6
5-7 .6
8-6 1.0
11-12 1.0
13-14 1.1
9-5 9
2-5 .8
5-2 1 I wasn’t able to get .45

[Yamamaya42]

something weird there, not really sure what, it SHOULD match the replacement, IF they are the same FBT.

[timmy]

The new flyback I have gives resistances and there are alittle different then the sams but that fly I can’t use if the donut tests bad that’s the flyback that kept red plating the hot. The numbers do match for the replacement flyback