Motorola ts907 low hv

[Yamamaya42]

jr_tech also has it, and he did the input impedance test on it, and it was 10m.

it a rather complicated thing to do with a voltage source and a 2nd DVM.

most DVMs of this type are, but most clamp meters are 1m.

[timmy]

So the msr- r500 is the one to grab

[timmy]

I guess that would explain why when I touch the probe I see a little tiny spark.

[Yamamaya42]

Originally Posted by timmy

I guess that would explain why when I touch the probe I see a little tiny spark.

It's almost like adding an extra resistor to ground.

[timmy]

Well I don’t know how much this meter was affecting the voltage outcome a guess maybe 10-12 volts lower then what it is normally.

[jr_tech]

Originally Posted by timmy

Well I don’t know how much this meter was affecting the voltage outcome a guess maybe 10-12 volts lower then what it is normally.

Not necessarily, it depends on the circuit being tested. For example, the pin 9 measurement (31 volts measured, 140 volts expected): pin 9 is connected to the 190 volt supply through a 3.3 megohm resistor in series with a 470k resistor for a total of 3.77 megohms! A 1 megohm meter would be a considerable load, dropping the voltage about 150 volts!
Lower impedance circuits (such as power supplies) would be hardly affected at all by the load of a 1 megohm meter.

jr

[timmy]

Ever since I accidentally let the hot red plate for like 40 seconds this is what I’m left with. Does this look like a bad damper. I am going to try a damper but I have both boost voltages so what’s this it looks like a bar generator but it’s not. Stumped again.

[Username1]

Originally Posted by timmy

Ever since I accidentally let the hot red plate for like 40 seconds this is what I’m left with. Does this look like a bad damper. I am going to try a damper but I have both boost voltages so what’s this it looks like a bar generator but it’s not. Stumped again.

This is some kind of interference. A 4X multiple of the Horiz Osc. Perfect bars
like that are from some Osc, you can see they are perfect repeating not waving
or anything like that. What happens when you change the Horiz. Hold?
Is it always there? Does not look like a bad damper. If you got good Boost V.
Damper is most likely good. But with respect to the bars, On the outside, could
possibly be Heater-Cathode leakage, or short? Just a guess.....

Unfortunately, this might be a job for Mr. Oscilloscope.....

Some frequency getting into video? Does it remain or change
with Brightness, or Contrast change...?



.

[Yamamaya42]

Originally Posted by Username1

This is some kind of interference. A 4X multiple of the Horiz Osc. Perfect bars
like that are from some Osc, you can see they are perfect repeating not waving
or anything like that. What happens when you change the Horiz. Hold?
Is it always there? Does not look like a bad damper. If you got good Boost V.
Damper is most likely good. But with respect to the bars, On the outside, could
possibly be Heater-Cathode leakage, or short? Just a guess.....

Unfortunately, this might be a job for Mr. Oscilloscope.....

Some frequency getting into video? Does it remain or change
with Brightness, or Contrast change...?



.

But this is what is bugging me

between the last pic posted and this
http://videokarma.org/attachment.php...7&d=1664286524

http://videokarma.org/attachment.php...1&d=1664977314
there has been 10-15% width lost.
which is strange
is the horz frequency way off? or the Damper damaged?

[timmy]

Originally Posted by Username1

This is some kind of interference. A 4X multiple of the Horiz Osc. Perfect bars
like that are from some Osc, you can see they are perfect repeating not waving
or anything like that. What happens when you change the Horiz. Hold?
Is it always there? Does not look like a bad damper. If you got good Boost V.
Damper is most likely good. But with respect to the bars, On the outside, could
possibly be Heater-Cathode leakage, or short? Just a guess.....

Unfortunately, this might be a job for Mr. Oscilloscope.....

Some frequency getting into video? Does it remain or change
with Brightness, or Contrast change..?



.

nothing changes it’s just there bright contrast horizontal nothing changes I tested all tubes although I can’t trust a tester anymore this don’t make sense I made k1 and put it in and while checking voltages that when I noticed the tubes red and that’s what was on the screen so I since put the k1 back in the way it was and still got these lines and I tried both hot new ones.

[timmy]

Already tried 2 new horizontal output tubes of course no change. One thing after another. So I need to find out what gives up when these tubes red plate to long.

[Yamamaya42]

A weak damper can cause low HV & insufficient horizontal width, but can also be a symptom of the horizontal osc being at the wrong freq, or a damaged HOT.

A new damper is a rather low cost first step in working out the problem.

[timmy]

Originally Posted by Yamamaya42

A weak damper can cause low HV & insufficient horizontal width, but can also be a symptom of the horizontal osc being at the wrong freq, or a damaged HOT.

A new damper is a rather low cost first step in working out the problem.

So if the frequency is low then that’s why the bars are there and are you referring to hot as tube or flyback. I have 2 new dampers coming tomorrow.

[Yamamaya42]

HOT = horizontal output tube FBT = flyback transformer.

Wait till you get the new damper, then once again do the setup for direct video input at test point B, and then adjust horizontal hold to try to get lock, once you get lock, there should be no need to adjust it again.

[timmy]

Well there is a difference in meters I have a cheapy meter from sears looks just like the one mentioned in the previous few posts and on one pin I checked was 188 v but with the cheapy meter it showed 203 v that’s a 15 volt difference wow I have to check all voltages again.