Motorola ts907 low hv - Page 52 - Videokarma.org TV - Video

bandersen · #**766** 10-24-2022, 12:02 PM

The resistors he ordered are fine.

Breach of the outer layer to what? The 750 for the Vishay is across the resistor and subject to the same power limits.

Generally speaking for all resistors. 1W can handle 350 volts, 2W, 500 volts, 3W, 750 volts across the resistor. Constrained by power disippation and ambient temperature etc.

timmy · #**767** 10-24-2022, 12:35 PM

As for diodes I can’t see putting higher amp diodes in only to feed a draw and that’s not fixing a problem the output diode is way to hot it is definitely not normal I can’t even touch it it’s that hot and I tried the cheapy diodes and the output still gets hot. It appears that when working all the controls are working color controls vertical I have to find out why they are hot as it may answer why the video is not there yet.

Yamamaya42 · #**768** 10-24-2022, 12:58 PM

Quote:

Originally Posted by timmy

As for diodes I can’t see putting higher amp diodes in only to feed a draw and that’s not fixing a problem the output diode is way to hot it is definitely not normal I can’t even touch it it’s that hot and I tried the cheapy diodes and the output still gets hot. It appears that when working all the controls are working color controls vertical I have to find out why they are hot as it may answer why the video is not there yet.

not really.

you have shown that you have good video with direct input, more than once I believe.

did you do a current test on this set now that you have a meter to do so?
was it more than 580-590ma?
if the original diodes are worn, it could explain them getting hot, and as mentioned before, the cheap ones are suspect as being counterfeit diodes, so they won't be much better, so putting in new 1a or 2a diodes should put the heating problem to rest.

Since you get good video from direct input, it is safe to say its not related to the power supply.

timmy · #**769** 10-24-2022, 01:32 PM

Quote:

Originally Posted by Yamamaya42

not really.

you have shown that you have good video with direct input, more than once I believe.

did you do a current test on this set now that you have a meter to do so?
was it more than 580-590ma?
if the original diodes are worn, it could explain them getting hot, and as mentioned before, the cheap ones are suspect as being counterfeit diodes, so they won't be much better, so putting in new 1a or 2a diodes should put the heating problem to rest.

Since you get good video from direct input, it is safe to say its not related to the power supply.

I did do the ma test and it was 550ma so that would suggest there’s no short I have these big diodes but don’t know the rating. And again after the set is on 10 or so minutes the voltage comes up within 5-7 volts normal voltage so now all the resistors are in v1 v2 and this video is so close. I noticed that the video would flicker on the screen as perfectly clear video so something is upsetting the video path.

Yamamaya42 · #**770** 10-24-2022, 01:41 PM

"So if this is only drawing 550ma then the diodes should not be getting hot not warm but hot. Another mystery."

This is within the norm range.

These diode are 57 years old after all, and after getting hammered each and every time the set is turned on and the caps charge up, it would not be any surprise that a pair on new ones would help quite a bit, and the price dif between 1a & 2a is almost nothing.

timmy · #**771** 10-24-2022, 01:57 PM

Quote:

Originally Posted by Yamamaya42

"So if this is only drawing 550ma then the diodes should not be getting hot not warm but hot. Another mystery."

This is within the norm range.

These diode are 57 years old after all, and after getting hammered each and every time the set is turned on and the caps charge up, it would not be any surprise that a pair on new ones would help quite a bit, and the price dif between 1a & 2a is almost nothing.

Yes that’s true I will have to end up changing them if I could only get video it is so close I could taste it there is a coil right at the antenna input maybe someone turned it so I’m going to turn in and out carefully watching exactly how many turns if no better I’ll put it back exactly where it was because it almost seems like a very weak input signal. Nothing to lose at this point.

jr_tech · #**772** 10-24-2022, 01:58 PM

Are c1, c2 and c3 staying cool?

jr

timmy · #**773** 10-24-2022, 01:59 PM

Quote:

Originally Posted by jr_tech

Are c1, c2 and c3 staying cool?

jr

Yes but one is in the area of the 550ohm resistor it gets hot in that corner.

Yamamaya42 · #**774** 10-24-2022, 02:04 PM

one you may want to try is listed on page 6 on the sams, step 5, coil A13, it is a visual only adjustment.

Yamamaya42 · #**775** 10-24-2022, 02:15 PM

Quote:

Originally Posted by timmy

Yes but one is in the area of the 550ohm resistor it gets hot in that corner.

the 20w 550 gets hot enough to cook a steak in a decent amount of time!

timmy · #**776** 10-24-2022, 02:15 PM

That’s the last coil in the IF I already tried that one turns in and out little if any difference put it back exactly where it was that’s the coil with the diode video detect.

timmy · #**777** 10-24-2022, 02:41 PM

I’m almost burned out with this set although i don’t give up easily but trying that coil no difference from befor just alittle but I put it back. I’m wondering about the .001 caps in L4 and L5 to be honest I already did the leakage test with the .1 cap to ground and the cap dropped to 0 so I guess this means they’re good.

Yamamaya42 · #**778** 10-24-2022, 02:42 PM

One thing to try is an AGC override, as shown on page 6 on sams, this is easy and needs few items and clip leads. Shown below. If it helps get a tuned picture , it means AGC is the problem.

500k potentiometer, linear.
9 v battery.

Wire the battery to the outer lugs of the potentiometer.
Hook negative line to chassis, and wiper of potentiometer to test point A on chassis.
Start sweep from 0v and work up from there to see if it gets a reaction.

timmy · #**779** 10-24-2022, 02:53 PM

You know I had a small feeling that the agc may be the problem because the agc pot does absolutely nothing if the agc is maxed couldn’t it distort the video like this. What could cause the agc not work or have it maxed. Wouldn’t the agc affect the video input B.

Yamamaya42 · #**780** 10-24-2022, 03:11 PM

Input at point B bypasses the tuner and IF sections, and thus leaves ACG redundant.

Thus the point if you can't get it to work, you can always build a simple video amp to get the contrast levels right and go that route.

https://www.electronicsforu.com/elec...ideo-amplifier