Motorola ts907 low hv

[Yamamaya42]

Originally Posted by timmy

The loss of sound has got to be why I can’t get video because I had sound initially it’s got to be the same problem unless it’s a really hard coincidence

it's the other way around, until you have clean video IF pathway, sound can't work, since sound is riding on top of it.
In some cases, (bw sets ) they take sound off after the video det diode.

[timmy]

Well maybe I should change every disc cap along the 3 IF tubes because there are no bad resistors that I found I tried different tubes there’s nothing left but these discs.

[Yamamaya42]

Before going that far, on the 3 tubes, taking voltage checks of pins pin 7,8,2,3 should tell you something.

voltage listings are on the SAMs.

[timmy]

Originally Posted by Yamamaya42

Before going that far, on the 3 tubes, taking voltage checks of pins pin 7,8,2,3 should tell you something.

voltage listings are on the SAMs.

Is that with an antenna on

[Yamamaya42]

Originally Posted by timmy

Is that with an antenna on

should not matter, but give it a signal, to keep it happy as it says, " taken with signal input".

[timmy]

Now this is interesting first tube 7- 191v 8 - 67v 3 - 15v 2- 8v Second tube 7-195v 8-59v 2-13v 3-13v Third tube 7-212v 8-214v 2-0v 3-2.6v

[Yamamaya42]

Stage 3 seems OK, but WTF, with 1 & 2, may be a hand in hand problem with AGC control V6 via K1, as stage 3 does not seem to be linked as 1-2 are.

[timmy]

K1 I checked the resistors in that and were good and that crazy resistor network thing there maybe one of those big 3 watt resistors are bad but I think they are wire wound

[timmy]

If c15 and or c19 were shorted would this cause the voltage loss on those 2 tubes

[Yamamaya42]

Since it's most likely the first 2 stages acting up, what I would do in most cases, is resistors first, caps second, even if the DVM says they are OK, don't trust it in this case.

Replace R38,R39,R40,R41,R42,R43,R44,R45,R46,R47,R48,R49, R50 with metal film types of high quality 5% or better 2%-1%, and then, if no change is seen, then look at the caps.

[timmy]

What caps are you referring to and how is this pulling the voltage down on those 2 tubes

[Yamamaya42]

Originally Posted by timmy

What caps are you referring to and how is this pulling the voltage down on those 2 tubes

these resistors set the bias for those tubes, and if they are just not right, things may go out of wack, even though they may test OK, under load they still may be suspect, so replacing the ones mentioned may help.

[timmy]

So are you referring to the ceramic caps because that’s the only caps at these tubes. What could possibly cause this with only the first 2 tubes and not the 3rd if there’s something on let’s say the first then the second should show good but what is in common with the both it don’t seem to make sense that resistors on only the 2 are bad and not the 3rd.

[timmy]

R45 on the schematic shows it’s a 560 ohm but when I measure it it gives me .551k but I know sometimes any resistor that is over 500 ohms it shows me it in k ohms same thing with the other 560 resistor. This one is green blue brown.

[Yamamaya42]

Originally Posted by timmy

So are you referring to the ceramic caps because that’s the only caps at these tubes. What could possibly cause this with only the first 2 tubes and not the 3rd if there’s something on let’s say the first then the second should show good but what is in common with the both it don’t seem to make sense that resistors on only the 2 are bad and not the 3rd.

This is based my own experience, and what others have told me about IF problems, added with the fact that ceramic caps are much less likely to fail than the older carbon composite resistors, this coupled with the indications of the incorrect voltage readings you gave pointing to problems with the first and second stages, meaning that is where the problem is MOST likely to be, I'm suggesting that you take the older carbon composite resistors in the first 2 sections out of the equation, even if they test OK with your DVM, who knows how they may act under full power and load, the end result, you will have better more stable and longer lasting resistors in there when you are done.

And then after that is done, then look for any possible shorted disc caps if it is still not working, but keep in mind it still may be an alignment issue.