Videokarma.org TV - Video - Vintage Television & Radio Forums

Videokarma.org TV - Video - Vintage Television & Radio Forums (http://www.videokarma.org/index.php)
-   Early Color Television (http://www.videokarma.org/forumdisplay.php?f=36)
-   -   Motorola ts907 low hv (http://www.videokarma.org/showthread.php?t=275174)

Yamamaya42 09-27-2022 11:58 AM

Quote:

Originally Posted by timmy (Post 3245156)
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 09-27-2022 12:05 PM

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 09-27-2022 12:39 PM

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 09-27-2022 12:48 PM

Quote:

Originally Posted by Yamamaya42 (Post 3245160)
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 09-27-2022 12:52 PM

Quote:

Originally Posted by timmy (Post 3245161)
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 09-27-2022 01:15 PM

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 09-27-2022 01:38 PM

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 09-27-2022 01:45 PM

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 09-27-2022 02:42 PM

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

Yamamaya42 09-27-2022 03:06 PM

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 09-27-2022 03:23 PM

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

Yamamaya42 09-27-2022 03:29 PM

Quote:

Originally Posted by timmy (Post 3245169)
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 09-27-2022 03:36 PM

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 09-27-2022 04:17 PM

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 09-27-2022 06:19 PM

Quote:

Originally Posted by timmy (Post 3245172)
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.


All times are GMT -5. The time now is 08:21 PM.

Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2026, Jelsoft Enterprises Ltd.
©Copyright 2012 VideoKarma.org, All rights reserved.