Motorola ts907 low hv

[Yamamaya42]

Originally Posted by timmy

It say it’s 15k but can’t measure it because the .2 that the coil is showing across the trap will show before the 15k. So how are they checked why would it have gone bad if it did.

Those types have brass communicators hidden under the plastic disc, they make contact with little carbon traces that are formed into the ceramic resistor base below it.

It looks fine, don't turn it cause it will make things worse.

[timmy]

Originally Posted by Yamamaya42

Those types have brass communicators hidden under the plastic disc, they make contact with little carbon traces that are formed into the ceramic resistor base below it.

It looks fine, don't turn it cause it will make things worse.

It’s not broke in anyway if it was turned it can be put back where it was correct.

[Yamamaya42]

https://www.robotroom.com/Trimpots-2.html

not exactly the same, but you get the idea!

[timmy]

Well now to figure out the next step.

[Yamamaya42]

Originally Posted by timmy

Well now to figure out the next step.

they most likely did not see the need for a full 3 terminal trimmer, and just got and oddball 2 terminal one.

[timmy]

This trap don’t have the center lead for wiper I guess it’s done under the blue cap

[timmy]

So if this were you where would you go at this point

[timmy]

When I put this chassis back in tomorrow I may try disconnecting the 2 wires from k1 that go to the first IF and see if this helps find this problem.

[timmy]

I also may put k1 back in the one I made up since for some reason I had a much clearer picture from pin 2 v2 when the new k1 was in but then again I replaced 2 22ohm resistors in v1 and v2 so maybe it’s the resistors letting more to get by in the iF interference to get the same clear pic Before doing the resistors I don’t know yet. And besides why is agc needed anymore anyway since there’s no more over the air broadcasting for the agc to amplify.

[Electronic M]

Originally Posted by timmy

I also may put k1 back in the one I made up since for some reason I had a much clearer picture from pin 2 v2 when the new k1 was in but then again I replaced 2 22ohm resistors in v1 and v2 so maybe it’s the resistors letting more to get by in the iF interference to get the same clear pic Before doing the resistors I don’t know yet. And besides why is agc needed anymore anyway since there’s no more over the air broadcasting for the agc to amplify.

You could manually bias the IF...Some cheaper portables and consoles like the Philco predicta didn't have AGC and simply had a local distant switch for bias control and expected the user to adjust contrast to compensate for signal strength....There may not be sufficient contrast range on your set to give it permanent fixed bias.
Modern RF modulators vary in strength so without AGC one unit might be too weak or too strong.

[Yamamaya42]

You already know that you could use the tuner subber to feed in signal at V2 pin 2, but it did not work at V1 pin 2.

but I do not think you tried to disconnect L3 point 2 ( leave R37 hooked up) and try to feed it in again at V1 pin 2 with that coil unhooked, you may have to adjust R14 and the gain of the subber.

If it still does not work, the fault is L4, and is likely not passing any signal, out of tune or bad.

If you DO get a picture, the fault is l3 or L1 L2.

Do not worry about the 7v on the grid right now the 6EH7 can still work like that, V2 did just fine with 7v on the grid, V1 will also.

So try it with L3 disconnected while feeding the subber in like you did with V2 and see what happens.

[timmy]

I already took v1 pin 2 wire off L3 I tried the subber and the video was not as good as v2 but I didn’t try the agc while I did this.

[Yamamaya42]

Originally Posted by timmy

I already took v1 pin 2 wire off L3 I tried the subber and the video was not as good as v2 but I didn’t try the agc while I did this.

so you got distorted video ?

that would mean that L4 is out of tune, most likely and prob L3

[timmy]

Originally Posted by Yamamaya42

so you got distorted video ?

that would mean that L4 is out of tune, most likely and prob L3

Ok interesting I’ll look into that tomorrow I’ll rule out everything you mentioned here L3 and 4 and I’m going to put the new k1 back in be the resistances are way out on the old one which may make a difference. I did get the new .001 mica cap but I did try a regular.001 ceramic that made no difference I don’t think a mica slim ale that much difference.

[Yamamaya42]

You should not have gotten a worse picture , unless somehow the signal was being overloaded, thus the reason to adjust the gain out of the subber down a bit.

but If it was messed up like feeding in from the RF input for the tuner, then L4 is suspect.