Motorola ts907 low hv

[Electronic M]

Originally Posted by timmy

I thought the whole screen goes up and down not the image alone.

Unless you have vertical underscan you won't see it move without video, and even if you do it's possible the osc will have enough jitter free running that you won't notice.

That said sets with electrical centering control typically run a DC current through the yoke to control centering. The pot it's self could be bad or the circuitry feeding it. Before declaring it bad though, I would definitely confirm operation with video fed in.

[timmy]

Pin 1 of 6cg7 is supposed to have 80v on it but it has a ridiculous 180v there this tv is full of surprises.

[timmy]

I wish I knew if someone fooled with the overall alignment of this set but if it has been messed with it can’t be to far out since I can make out some things on screen but of course it’s distorted.

[timmy]

Has anyone ever had a video detect germanium diode test good but be bad in circuit.

[Yamamaya42]

What you would see if your IF section was VERY messed up...
Absolute and total randomized garbage on the screen as you try to tune in something, wildly changing color (unless color killer is turned down), herringbone patterns that will react to fine tuning, but no real video info getting through at all.

You could try to replace the video det, but it most likely won't help as the problem is most likely before it.

So it seems you have 2 choices.

1)
Find someone nearby with the equipment and knowledge to help you debug and align the tuner/ IF sections.

2)
Rig it for direct A/V input, and bypass the front end for now using a easy to build video amp to match the level needed for the set.

[timmy]

Well I put a new video detect diode in certainly was not an easy thing to do so I’m going to try it and as for alignment there is only one coil that shows the slug was moved it’s the same coil where the diode is A4 so if that was messed with then if I’m careful I could turn the slug in or out counting the turns in or out and see what occurs I have nothing to lose at this point.

[timmy]

No difference but the video injecting still works and I did notice the ac waving in the screen for the first few minutes caps are good unless ac is getting in somewhere. The block lines are not in the picture the camera is causing the lines.

[timmy]

How can I stop the blue arc that is between the rectifier and the 2 wires for the 3 volt heater

[Yamamaya42]

Originally Posted by timmy

How can I stop the blue arc that is between the rectifier and the 2 wires for the 3 volt heater

inducted corona, mostly harmless, my hoffman colorcaster did the same thing, just keep the wires as far away from the tube as you can, I did this by cutting the bottom off an old pill bottle and putting it around the tube as a guide/form to keep the wires away from the tube.

[timmy]

Well at this point it doesn’t matter how much current this set is drawing because the 3 voltages are low again and I still think there is some stray voltage getting in somewhere affecting the video and the voltages. being the output diode gets really hot which I’m sure is not supposed to get this hot.

[timmy]

Thought it may break the glass on the tube. Smell of corona is not bad it cleans the air.

[Yamamaya42]

Again, don't take the voltages listed in the SAMs as gospel, expect them to differ by some degree.
Your screen showing good video with direct input is a indication that power is stable.

As for the hot diodes, this is not suprising, they are under heavy load, but if there is doubt, replace.

As suggested before, these are cheap and much better than the OEM ones.

https://www.mouser.com/ProductDetail...2B4kkscA%3D%3D

[timmy]

With video injected the horizontal and vertical are good stable picture but I can’t imagine where the stray voltage could be coming from because obviously it’s still pulling the voltage down but it seems not all the time or even where to start to look. There is a 390 ohm resistor to ground I clipped it and it measures 390k the voltages are low in v1 v2 but if I leave the resistor off the voltages jump up.

[Yamamaya42]

My set has a 3A3-C, and the heater wires were getting a bit close and causing a blue glow, all I did was use a plastic spacer around the tube that was about 10-15% larger than it's diameter to keep the wires away, it's working perfectly.

[timmy]

Problem I have is I only have a 360ohm resistor not a 390ohm. I could try it see what happens.