Motorola ts907 low hv

[timmy]

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

[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]

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.

[Yamamaya42]

this is taken from the b&k precision 1077b television analyst manual, it's for the most part what you are doing to debug the IF

http://suzaku.live-evil.org/if-111.jpg
http://suzaku.live-evil.org/if-222.jpg

[timmy]

The primary of L4 has the red cap I don’t know yet if it’s a mica but maybe I can’t use a ceramic to test like I did because when I wired in 2 ceramics and had the wire off L3 and had the subber on pin 2 of v1 I took off the ground on both caps and it made no difference in the video at all so maybe while I have the chassis out I should put the mica in and the other .001 so that’s done.

[timmy]

So if the primary cap the red one is not a mica then putting a mica in same value should be ok.

[Username1]

Good Morning:

Before I run off to work today, there are a number of things I would like to
see you test if you want to & have the time......
Both at the IF section, and again at the HV section.

At the IF Section, I know this may sound silly at this point, but, I think you
should check the input RCA jack the center connector where the signal goes
in, I think you should check this to ground with the ohm meter, to be sure
it's not grounded.... Please post the actual reading as well.
I think you should disconnect R23 at pin 3 of L3, and Disconnect Pin 1 of L3
and then put in your DC AGC bias circuit for Point A. Fire it up and see if you
can feed a signal through..... Be sure to sweep the voltage on your little AGC
bias circuit. If no signal, then I think you should reconnect everything,
disconnect pins 2, & 3 of L4. Take your tuner subber and ground pin 2 of L4,
and using your coupling cap attache the tuner subber to pin 3 and see if a
signal makes it to the screen..... Without a plate voltage there I'm not sure if
it matters to leave V1 in for this part, or take it out.

Not sure how I feel about disconnecting pins on K1 because it can be
overridden by the AGC Bias thingie. But If you really want to remove
a Pin & Test, I would remove only pin 5. Be sure you use new batteries
in all of these things for testing.

Other thing I would like to see is a resistance or Ohm reading from these
points to compare against the Sams for the following areas.....

Tube | Pin | Sams Reading | My Reading |
--------------------------------------------------------------------------------
6JM6 | Plate Cap Both | 22 Ohms | ? |
3AT2 | Plate Cap | 622 Ohms | ? |
1V2 | Pin 9 | 21 Ohms | ? |
6BK4 | Pin 5 | 800K Ohms | ? |
6DW4 | Pin 2, 7 | 24 Ohms | ? |
6DW4 | Pin 9 | 240K Ohms | ? |

-------------------------------------------------------------------------------

Please double check the resistance table & be sure I did not make a mistake
here. Also observe the little caveats posted in the Sams about each reading.
I'm interested in these as a double-check for flyback wiring, just -in-case.

Don't forget to stop for coffee breaks now & Then and have
a good lunch & think about next steps.
Never Give Up, Never Surrender.....

Have an Awesome Day!


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