Motorola ts907 low hv

[timmy]

Originally Posted by Username1

Hi!

I'm wondering about this pic:



If that extra bright vertical area in the center of the picture is not from the camera
then there may be some timing issue going on with the damper circuit.
But right now I don't think you should do anything about it......

Removal of the 1St Chroma Bandpass Amp Tube V19 Could mean the bars
actually do originate somewhere close. If you look at the Oscilloscope pics
on the schematic of the plate of V19, (Pin 6) you can see a burst group of spikes
for each scan line, This could be your bars if possibly the Burst Osc is not
at the correct frequency, Or this circuit, or any circuit in this video, or Color
processing area is not operating correctly.

You will have to start by checking voltages on each of these tubes......
Put it on a post Pin X, Expected Reading, Actual Reading. Lets All See them.


The Specs .pdf posted a few pages back of one of your meters, and at this
point I'm not sure which, or how many you have, but anyway one of the
meters said it is made to operate within 40 - 4Khz when measuring AC,
I believe..... So be aware the Horiz. circuit is 15Khz, and the color circuit
is some digits above 3Mhz, A question for Cheap-O-Meter accuracy....?
Same for clamp AC Current meters..... Is the clamp picking up 15Khz High
voltage stuff? is it effecting any readings...?

Not sure about the width of the bars makes a big deal not or not. Definitely
could be a decaying "ring" off the Horiz circuit making it's way to the video
or color circuit somehow..... Not ready to put any money on it today...

You have your hands full here..... I'm starting to like the fire idea you floated
a day or two ago.
You know Monday is a holiday.... You might just wanna drag this thing out to
the field behind your house, set it on fire, bring out some Marsh Mellows, a
few hot dogs, and make an afternoon of it.
Post a few pics so we can all celebrate the demise of this thing.....



end transmission....


.

As for the voltages I’ll be looking into that and the line in the center if it’s possible it’s a damper I since put a new one in.

[timmy]

Well sams shows 140v on pin 3 of the hots there’s only 100v and the 10k 20 watt resistor is good tried 2 new hots still 100v the 330 resistors are good pulled the 6bk4 cap still 100v and the 385v source on the end of the 10k resistor is there so this flyback may be screwed and it’s new. If I pull both hots the voltage is ok on pin 3. Ok update problem solved I hope the bars are gone don’t know yet if I’ll have video that’s the next post.

[Electronic M]

If pin 3 of the hot is the screen grid as I suspect then it being low indicates excessive screen current.
Excessive screen current occurs when there isn't enough plate load. If the damper is weak or open the screen should say like that (it will be worse if damper or H out plate lead is open). Or if circuits that normally load the flyback are open or otherwise not drawing sufficient current (even a detuning in the yoke or other resonant circuit could cause this).

The flyback is probably OK...If the flyback had shorted turns the H output screen voltage would skyrocket above rated voltage. Basically the cathode emissions is split between screen and plate (the vast majority to plate). So if the plate takes less of the fixed cathode emission the screen takes up the slack, but if the plate takes more the screen gets less.

[dtvmcdonald]

If I were you, located where you seem to be, I'd try to find somebody with a 100 MHz scope and a signal generator and make up a couple of bias boxes (9 volt battery and 100K or so pot across it and some clip leads, two separate outfits.)

Have the knowledgeable scope guy visit you and start at the antenna and get the B&W signal to the CRT, with the horizontal and vertical oscillators and outputs completely unplugged. The set should be on a variac set so the B+ is not too high and the filaments not too low.

Next try to get the horizontal (and boost) working, still with a signal getting through with the AGC still running on the bias boxes.

Also remember ... this has been said before but its good to be reminded: never, ever, run the horizontal ourput tube with the plate disconnected or no B+ on it and its screen at normal connection. Its OK to run the screen at something like 20 volts if you can find that somewhere. Usually one just unplugs the horizontal output tube.

I had a recalcitrant horizontal intermittent in my CT-100 and that's what I did ...
using the scope on the Horizontal circuit with the AGC set with a bias box showed that its was the oscillator part that was intermittant. It never identified the bad part so I replaced them all, all resistors included, a second time. That fixed it.
I would never ever have figured all that out without scoping with the AGC fixed.

[timmy]

Found a few problems corrected but the b+ hangs in ok but the 145 190 275 drop off like 20 - 25 volts on each I think it’s a lousy power supply cap the 450v 50uf and possibly the 450v 80uf I keep changing caps then it’s ok then voltage drops again then another cap I’m out of caps.

[timmy]

None of this makes any sense anymore turn it on and as the tubes light the 3 voltages drop and of course the hv is low and I subbed caps made no difference and no tubes are red plating except the hot tube sometimes upon turning on even with the low hv voltages are still very low. This is just crazy already.

[timmy]

Horizontal oscillator 6 150=169 3 150=169 2 1=0 7 10=.8 9 -15=-14 1 .5=.7 where is 169 coming from should be 150.

[jr_tech]

Originally Posted by timmy

Horizontal oscillator 6 150=169 3 150=169 2 1=0 7 10=.8 9 -15=-14 1 .5=.7 where is 169 coming from should be 150.

Was the yoke plugged in during these measurements?

jr

[Username1]

169 means the tube is not producing the nice spike to drive the Horiz. Output tubes
properly, Especially with the Cathode voltage so Low.

Low HV Probably from Poor Horiz. Output drive to G1's, If it's too high, HV will be low
and Tubes will overheat, and will take your Power Supply Voltages down....

You must have some intermittent poor operation of the Horiz. Osc Circuit.


There are a number of things going on, Osc. Possibly not working right, Causes
H Output to overheat, and brings down PS Voltages.... Get the H. Osc working
right, right frequency, right signal shape, Size, etc. FIRST.


.

[Yamamaya42]

So, again this is being hamstrung by the lack of an oscilloscope, for the most part.

https://www.ebay.com/itm/14475044830...6T4YA&LH_BIN=1

semi OK ones for the price, have a feeling it won't last long b4 someone them all.

[timmy]

Pin 1 of horizontal oscillator has a .5 cap that was 100v but I had put in a .5 630v would this make a noticeable difference. Pin 2 1v but I get 0v and pin 1 .5v I’m getting -7.0v

[Yamamaya42]

Originally Posted by timmy

Pin 1 of horizontal oscillator has a .5 cap that was 100v but I had put in a .5 630v would this make a noticeable difference. Pin 2 1v but I get 0v and pin 1 .5v I’m getting -7.0v

what cap # is that on the SAMs? :O

[timmy]

C81 but the sams don’t show it in the arrows to identify where it is but it’s there. Another typo

[jr_tech]

Originally Posted by timmy

C81 but the sams don’t show it in the arrows to identify where it is but it’s there. Another typo

Shown on the picture on page 5.

jr

[Yamamaya42]

Originally Posted by timmy

C81 but the sams don’t show it in the arrows to identify where it is but it’s there. Another typo

SAMS shows it to be between r119 - r121 and has a tie to ground with r120.

thus I was a bit confused when you said "Pin 1 of horizontal oscillator has a .5 cap" to me that meant C78, :O

It would be helpful if you gave part numbers from the SAMS to make it more clear :P

that part of the circuit is for sinewave shaping, the larger value volt cap should not matter, BUT value and type WILL.