Motorola ts907 low hv

[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]

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.

[Username1]

Originally Posted by 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 288 v but with the cheapy meter it showed 203 v that’s a 15 volt difference wow I have to check all voltages again.

Uhmmm.... You know the difference between 203, & 288 is not 15......


Also, Impedance is AC resistance.

You can calculate the DC resistance, or see it's effect on a circuit under test
with a simple test. Take a known voltage source like a good 9V battery,
connect 2 - 1meg-ohm resistors in series, measure the voltage across each
with your meter, and see what the two numbers add up to. Too far away
from 9V and you know your accuracy is going away. Do the same test
with 10Meg-Ohm resistors etc. Up or down to know at what point you
will begin to get poor readings.....

EX. With the 10Meg-Ohm resistors you measure 3.5V across each, in this
case adding up to 7V. On a known good 9V source. Your meter is loading
the circuit and effecting the accuracy of your work.

This was a bigger problem with needle type meters that were 20K-Ohm/Volt.
resistance loading on a DC scale. Most had it printed on the meter face so
you knew when to suspect meter loading. Most Digital meters are very high
input resistance to DC.


.

[timmy]

Typo it’s 188v

[timmy]

I’m going to try a new damper but I actually have both boost voltages if the damper is bad I shouldn’t have these voltages so that brings me to what are the bars on the screen that look like a bar generator but it’s not.

[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]

Now this don’t make sense using the cheapy dvm on the 200v scale pin 3 of v6 is showing 25.6v and with the other dvm it shows 8.3 so chances are the right reading would be the cheapy meter but 25.6 it supposed to be 2.5v

[Yamamaya42]

You say you “put in a new K1 and was checking voltages” when things got all weird, when did the screen start to do that?

After the new K1 put in, or after it was in AND you started checking voltages?

[timmy]

Originally Posted by Yamamaya42

You say you “put in a new K1 and was checking voltages” when things got all weird, when did the screen start to do that?

After the new K1 put in, or after it was in AND you started checking voltages?

I had it on the bench and put in k1 and I checked voltages on the bench then put it in to find those bars but I since took k1 out only to find I put of all things a 680ohm instead of 680k so the original k1 is in now but still with k1 in and being wrong resistor initially I had no bars it seems more that the hot got red.

[Yamamaya42]

That was... bad.

You will prob have to meticulously go over the IF section checking every resistor and coil for damage, V6 area included, if you remove 3rd IF V3, do the bars go away?

[jr_tech]

Originally Posted by timmy

I had it on the bench and put in k1 and I checked voltages on the bench then put it in to find those bars but I since took k1 out only to find I put of all things a 680ohm instead of 680k so the original k1 is in now but still with k1 in and being wrong resistor initially I had no bars it seems more that the hot got red.

Are you testing voltages “on the bench” without the yoke, crt and other cabinet mounted components being plugged into the chassis?

jr

[timmy]

Even with that wrong resistor I still had a full screen now vertical is collapsed. I don’t get it I never touched anything to do with vertical oh and I put the damper in but with no vertical I don’t know what’s happening now. Time to have a bon fire featuring Motorola

[Yamamaya42]

loss of 640v boost would cause vertical to fail.