Motorola ts907 low hv

[timmy]

I don’t know at this point if the hot both get red for to long if it would damage anything other then the 2 hot

[Yamamaya42]

Originally Posted by timmy

No I didn’t make the couplet until I get resistors I only had the 680k the others are so so but in trying to set the -45 I noticed I can’t get it to -45 and the screen is dim at 22kv and with the meter on number 5 of the hot my meter is showing 1.3 amps on the ac scale but I had it set to dc but I know this meter if there is excess current it shows on the top scale and you are right none of this makes sense but I will tell you that I had to adjust the horizontal coil to get the oscillator going initially after getting a better signal to the IF but I took to look and the hot both turned red so I don’t know if I damaged the flyback because of that I don’t know and I’m preparing put the original flyback back in because I don’t trust the new one this maybe affecting the agc and the IF.

I'm still quite confused by what you were doing here.
"trying to set the -45 I noticed I can’t get it to -45 "
what were you doing here?

what steps taken, what was adjusted , if anything?

[jr_tech]

Originally Posted by timmy

the screen is dim at 22kv and with the meter on number 5 of the hot my meter is showing 1.3 amps on the ac scale but I had it set to dc but I know this meter if there is excess current it shows on the top scale

How exactly is the meter connected to pin 5? Are you perhaps trying to use the AC-only clamp on jaws to measure DC?

jr

[timmy]

Originally Posted by Yamamaya42

I'm still quite confused by what you were doing here.
"trying to set the -45 I noticed I can’t get it to -45 "
what were you doing here?

what steps taken, what was adjusted , if anything?

The horizontal oscillator/ hold coil I was able to adjust it to -45 with no problem because I found when it’s adjusted it’s one less thing I need to do but I know now that if the agc is trying to do what it does well then I waisted my time but now I’m stuck with a dim screen. And when it’s set to -45 the hv adjusts easily but now the hv won’t go over 22kv.

[timmy]

Originally Posted by jr_tech

How exactly is the meter connected to pin 5? Are you perhaps trying to use the AC-only clamp on jaws to measure DC?

jr

Ground and positive on pin 5 no clamp I think my meter was sensing ac from somewhere.

[jr_tech]

Originally Posted by timmy

Ground and positive on pin 5 no clamp I think my meter was sensing ac from somewhere.

That is the wrong way to connect a current meter!
Current is measured in series between the source and the load.
https://www.allaboutcircuits.com/tex...ammeter-usage/
Your meter as well as the circuit could be damaged by such mis-use.
jr

[timmy]

Originally Posted by jr_tech

That is the wrong way to connect a current meter!
Current is measured in series between the source and the load.
https://www.allaboutcircuits.com/tex...ammeter-usage/

jr

I know how to measure current I wasn’t measuring the current just the pin5 -45 to get the hv right.

[jr_tech]

Originally Posted by timmy

I know how to measure current I wasn’t measuring the current just the pin5 -45 to get the hv right.

So you weren’t trying to measure current?

But your meter did this: “with the meter on number 5 of the hot my meter is showing 1.3 amps on the ac scale” ?
Confusing!

jr

[timmy]

My dvm I think picked up stray ac or ripple other stuff I had worked on this has happened even when it’s on dc if it picks up any ac it will display it on the top ac scale dc is on the bottom.

[Yamamaya42]

That is not how horizontal is adjusted on the set, in fact -45v is not an adjustment at all, but as I indicated, an voltage that shows that the oscillator is running and does not have to be exact, the frequency, timing and waveform there is what matters, and this is set by horz hold and hoz afc.

The ONLY measurements in the area are at the cathode of the HOT, and you do not have the meters to do this, you would need 2 meters that can measure current up to ½ amp, and do both tubes at once, cutting pin 2 from ground and putting a .47 uf cap from pin 2 to ground on both, and then measuring the current across that cap 120ma, both, but since this set does not seem to have a horizontal efficiency coil to adjust, this is not needed on this set.

What ever mistake you did in this, you most likely cremated your damper tube, and it will need to be replaced, it is rather weak and easy to damage, much more easy to hurt than the outputs.

[timmy]

So are you saying that with the hot red plating cooks the damper tube. So if 770 boost is gone then the damper is gone.

[Electronic M]

Certainly possible. I have a Silvertone CTC-15 clone that would short it's damper and completely loose HV if the horizontal frequency went too far off...It blew at least 2 good tubes when I was working on it. That was the first color set I restored to working and it sat a few months with dead HV because until I borrowed the damper for another set I and discovered it had failed I didn't retest it because it tested good before I lost HV.
That same set later had a weak damper that would test great unless you held the test button down for like 30+ seconds to get it to slump. That weakness caused unusably low HV.
Some problems are spooky in that the failed component WON'T test bad unless subjected to conditions more extreme than the normal use case of the test equipment.

[timmy]

Well back on track I made the couplet and found out where ac was riding on dc a defective power supply cap no more ac.

[Username1]

Hi!

A few observations....
1. When the Horiz Output tube in Timmy's set gets red plates, it's most likely due to a
poor horiz drive to G1, from improperly working Horiz Osc. Remember the damper
rectifies the collapsing coil field and makes the current available for use in other circuits.
It may be a good idea to replace it anyway since it does a lot of work.....

2. Timmy states that he adjusts the -45V to the G1's of the Horiz Output Tubes. He does
this with the Horiz. Hold control. By adjusting the frequency the resulting bias on
the G1's of the Horiz Output tubes moves closer to normal. Is it a good thing? Who
knows. - but it should keep the output circuit safe. Best idea would be that when
he feeds a signal to the tv and it gets a picture that locks, after that leave it alone.

3. Yamama suggested that once the tv gets a picture and the HV is normal, PS Voltages
are normal, that Timmy leave it alone for hours and see how long it runs like that. -
I Like that idea a lot! You really need to determine what causes the two states that
this tv operates at, A) Semi-Working, and B) Low HV and Red Plate HV Output tubes...
What causes these 2 states? Is it taking the chassis out? Putting it in?
4. AGC, a normal tv will work without HV fluctuating with an overloaded signal, and
with no signal at all it gets snow, and in both conditions no glowing plates on the
horiz output tubes.....

One thing Timmy needs to do is measure the AGC line voltage when the tv is working
and when it's in its Overheating tube state and see if there is a difference. If so, then
you need to set up a battery that can force that line between the 2 levels and see
if the AGC is the ultimate cause of this TV taking 34 pages to track down this problem.

Could the AGC be causing IF circuit tubes to be drawing too much current? If you are
going to order a new damper tube, then order a Voltmeter with 10A Current scale
too, and get one that is NOT Auto-range, get one that you have to turn the dial to
read 10A, 2A, etc. I'll say it again with a 10A Scale, the resistor inside the meter
is actually a piece of wire with almost 0 ohms, and you will have almost 0 resistance
added to the circuit when you measure 500ma, or 1/2 Amps.


.

[zeno]

Not sure where we are now but.......
To measure H Out current you need to open the cathode pin from GND
and put a ampmeter in series with it. Depending on the meter you should
decouple the cathode with a cap to smooth it out. It goes in // with the
meter.
SAMS has instructions on value of cap & procedure.
Adjusting the H. osc ( hold) will effect the G-1 negative voltage.
Keep in mind the whole thing by design needs to be in resonance
to be happy. If the G-1 is in spec you are good till that point.
A freq counter or scope can show you if its at 15,750.

AGC as a rule goes to the RF amp & IF # 1 & 2.
SAMS will show AGC voltages either with or without a strong signal
or both ways. AGC problems are VERY rare, I cant really remember
many in 40 yrs & tens of thousands of sets.

73 Zeno
LFOD !