Motorola ts907 low hv - Page 55 - Videokarma.org TV - Video

timmy · #**811** 10-25-2022, 03:22 PM

All I could do now is look at the old caps that are still in the chassis more so the ones that tie to ground along with all the rest of course they are old and should go and if there’s a bad one I will know it.

Yamamaya42 · #**812** 10-25-2022, 03:24 PM

any leakage from heaters should have been AC, If it was DC, then it was most likely residual voltage from before.

Prob nothing.

timmy · #**813** 10-25-2022, 03:31 PM

I did get an ohms reading but I didn’t write it down.

timmy · #**814** 10-25-2022, 04:35 PM

Well how about this scenario being the hv jumped up and the voltages went up on the 2 IF I could possibly have a cap at the horizontal oscillator that may be defective and that would possibly change the frequency and there for mess up the agc and down to the IF strip. I never had a new bad or defective cap but I guess it’s possible.

timmy · #**815** 10-26-2022, 06:49 AM

I’m wondering why if v6 is pulled then there is no horizontal oscillator v12 it don’t run shouldn’t the oscillator run without v6. Maybe this is my problem if the oscillator should run by itself. I’m not sure looking at the block diagram if v6 is needed or not for the oscillator to run.

Yamamaya42 · #**816** 10-26-2022, 07:40 AM

I'm rather unfamiliar with the way Zenith did their horizontal oscillator circuits, it's clear that this set has a clone of the Zenith and not RCA, or some other kind.

Very close to this.
https://www.earlytelevision.org/pdf/...sams_757-4.pdf

do remember , the horizontal oscillator is a phase locked loop, and where I'm not sure of all the aspects of how it's implemented in this set, but, removing V6 is most likely breaking the feedback chain, and the oscillator won't start w/o it.

timmy · #**817** 10-26-2022, 09:13 AM

Is there a reason why L42 gets really hot along with the focus coil L42 measures 35ohm so far it’s still good but why both really hot these 2 tie into the agc and noise gate kind of odd being the problems in the agc circuit. When I first got this set the 100k resistor on the focus coil was burned.

Electronic M · #**818** 10-26-2022, 10:16 AM

Quote:

Originally Posted by timmy

Well how about this scenario being the hv jumped up and the voltages went up on the 2 IF I could possibly have a cap at the horizontal oscillator that may be defective and that would possibly change the frequency and there for mess up the agc and down to the IF strip. I never had a new bad or defective cap but I guess it’s possible.

The horizontal running off frequency shouldn't effect AGC a noticable amount. If you have ever misadjusted the horizontal hold on a working set you'd see that the video amplitude stays very close to normal with the hold out of locking range....If the set by design lost IF signal because misadjusted hold screwed up AGC then the sets wouldn't be able to receive a signal unless the horizontal miraculously synced up to a station without signal....No maker would sell something so Mickey mouse.

Yamamaya42 · #**819** 10-26-2022, 10:30 AM

Again, the whole point of applying the 0-9v sweep to the AGC test point was in hope that the circuit may have been malfunctioning, and by giving it external control power, it would have given the IF a chance to pass something through, but this did not help, again pointing at an alignment problem, and not related to any other areas.

EDIT==

EM addressed the resistor issue before...
"I think I have heard that if the coil is at it's extremes it will burn that 100K resistor."

timmy · #**820** 10-26-2022, 10:53 AM

But I have been looking for a draw down in voltage as a possible reason video is screwed up and this maybe it I don’t know but the focus coil and L42 get really hot L42 got so hot that the glue holding the coil in let loose and the coil fell out so I put hot glue and I just noticed the coil fell out again heating the hot glue. The resistance check on v6 and v12 were good so the focus coil and L42 both are tied to 2 locations in the agc feedback circuit the 2.2pf and the 470 pf disc caps c96 130pf is new so if the focus coil is bad or any one of the 2 caps along that line are bad then maybe this could solve it. Amazing but I found a new focus coil.

Yamamaya42 · #**821** 10-26-2022, 11:42 AM

Any issues that may, or may not be with the focus coil area are not related to the tuning / IF or AGC issue, if it was, you would have seen a substantial change in video on screen when AGC test point A was given a bias sweep from 0 to 9v.

This means that no matter how AGC tries to set gain, no matter what the voltages are on V1 & V2, or the tuner, no video is going to get from the tuner to the detector diode w/o getting corrupted.
The alignment is wrong.

timmy · #**822** 10-26-2022, 11:51 AM

There are voltages between the 2.2 cap if this cap is bad then it would upset the sync sep and as been stated before is that if the sync sep is not right I won’t get video or be able to tune anything in. The voltage on pin 6 IIRC was low and should be 145v and the agc does nothing as it should change voltage via the agc pot. It’s just my thought I could be wrong.

timmy · #**823** 10-26-2022, 12:04 PM

I know I’m being stubborn but if the alignment was so far out then I would not have had the picture flicker in clear as can be for a second and I have 2 components getting very hot for a reason and need to find out why like the diode getting hot heat equals voltage so I need to find out why and if it corrects any other problems then that’s a plus.

Yamamaya42 · #**824** 10-26-2022, 12:54 PM

What you may see in the first second or two is not relevant, as how any given receiver behaves before all the components come up to normal temperature and operating voltages is very different from up in a stable state.
Thus the alignment instructions clearly state “allow a 20 minute warm up period.”
What you are most likely seeing is the IF/and or tuner passing video before things have fully come up to power and stabilized, this is not unusual, the alignment method of course would be to get it to pass video when it's fully up and warm.

Also, the sync sep has been shown to be in a good state already, if it was not, you would have no video lock, and or unstable video with the direct video input.

timmy · #**825** 10-26-2022, 12:57 PM

Quote:

Originally Posted by Yamamaya42

What you may see in the first second or two is not relevant, as how any given receiver behaves before all the components come up to normal temperature and operating voltages is very different from up in a stable state.
Thus the alignment instructions clearly state “allow a 20 minute warm up period.”
What you are most likely seeing is the IF/and or tuner passing video before things have fully come up to power and stabilized, this is not unusual, the alignment method of course would be to get it to pass video when it's fully up and warm.

Also, the sync sep has been shown to be in a good state already, if it was not, you would have no video lock, and or unstable video with the direct video input.

Ok true but I still have the focus coil and the peaking coil very hot this is not right for only a minute on the focus coil could be shorted but I didn’t check it yet.