Motorola ts907 low hv

[Yamamaya42]

Originally Posted by timmy

I dont know half of what you guys know when it comes to these tvs but I don’t get why the voltage drops once they are plugged in. Can I test the selenium diode with a dvm.I have noticed that when the vertical is running you can usually here it at the yoke all my other color sets I was able to here it this one I don’t. So if the vertical is not running that maybe pulling down the b+ since there is a 385v on the primary side of the output transformer or maybe no running at the correct speed.well I know if the vertical quits then I have a horizontal line but maybe not running at correct speed.

I have said it, and so have many others, you need to get better equipment, because now, you are just going on assumptions, and as long as you are, you will keep going in circles no matter what you try to do.

You NEED a better DVM that can measure the current draw right after the main diodes, you need to know what the draw is with NO guessing. 580ma? more? less?

And as others have said, you need an o-scope.
is the ripple after L54 1.5v? more? less?

ALL OF THIS is important, And can't be done with what you have right now.

[timmy]

I know I know but I cannot spend crazy money for just this set nothing in stone that says I’ll be working on more sets in the future so with that said one day in the very near future I’ll post when it’s fixed. I have nothing else to do during the day.

[Electronic M]

Wasn't this set listed on eBay for like $225 before you bought it (I remember because before the ETF meet I was considering buying it)?

If you choose wisely you could get 4 scopes and a decent budget DMM for what this set cost.

[reeferman]

It's definitely time to throw in the towel on this set and cut your losses.
You've learned from this encounter.
Don't feel bad; it happens to all of us in life.
There are future projects with your name written all over them.

[Yamamaya42]

I have pointed this out before.

https://www.amazon.com/AstroAI-Multi...882160&sr=8-34
https://www.amazon.com/Crenova-Auto-...1882412&sr=8-7
https://www.amazon.com/Multimeter-Co...1882412&sr=8-8
https://www.amazon.com/Ranging-Digit...1882412&sr=8-6


here is 4 examples of what I call cheap throw away DVMs, I have 3 like these, which I use for risky testing, and not afraid to damage them, 95% of the time they agree with my high $ Fluke meters, which i use when i want best accuracy, like alignments.
The cost is so low on these, no reason not to have 1 or 2.

here is just a few hand held o-scopes.
https://www.amazon.com/Quimat-Oscill...ustrial&sr=1-5
https://www.amazon.com/Oscilloscope-...ustrial&sr=1-3


not so cheap, and will take a bit to learn to use.

[timmy]

Yes they are nice good prices as for the dvm there is no need to condem the one I have already only my meter don’t go above 400ma but right now what good would it be for me to know what the ma is I already know there is a draw down so to look at a meter showing me 700-900ma won’t tell me where it is only that it’s drawing more then it should be which I know already. And the horizontal oscillator loss is due to the current draw on the b+.

[Yamamaya42]

But right now, you are working in the dark, you need to know what it is exactly, other than beyond the range of your meter (400), is it taking 500ma? 560? 580? 600-610ma? All of this will be telling you something, you have to know what the draw is first, then if it's too much, then look for the reason of the draw, if it's not, like below 400-500ma, then the power supply may be having a problem putting out enough power in the first place, this would be evident by excessive ripple output, which would wreak havoc with all circuits.

[timmy]

Ok I have another dvm I’ll have to see if that one goes above 500ma and if there is excessive ripple then that would mean bad caps or maybe diodes and what’s going to show me ripple other then a scope.

[Yamamaya42]

Yes, bad/weak diodes or leaky caps (c151/c152) would cause excessive ripple before/after L54, and limit the power output, thus the wave seen at L54 would be much higher than 1.5v ptp, and the power supply would be struggling to put out full power.
On the other hand, if it is overloaded, like say over 600ma, then the problem is external, as others have said, don't take the 580ma as gospel, expect -/+ 10%
But the first step, as others have said is to know for sure.

[timmy]

The other meter to low so that’s out but I did look at the dvm I have been using and the range says in the book 400ua 0.01 and the other 2000ua 0.1 so maybe I had the range wrong.

[Yamamaya42]

Originally Posted by timmy

The other meter to low so that’s out but I did look at the dvm I have been using and the range says in the book 400ua 0.01 and the other 2000ua 0.1 so maybe I had the range wrong.

it just does not have the range needed, 2000ua = 2 milliamps.

you need something with a 10a range, cause you are dealing with 500ma 1/2a almost.

[timmy]

Ok so the crt holds lots of voltage even after turned off so from the beginning I’m getting buzzed from the hv cage even when off so I may have hv leaking to ground.

[Yamamaya42]

Yes, it's a giant storage capacitor, and it will always find ways to get you!
Best to discharge the anode after it's been on so you don't get zapped, it can't really hurt you, unless you have cardiac issues, as it can scare the crap out of you, and cause you to yank your hand back and cause nasty cuts in the sharp edges all around.
If I had a dollar for every time I have been zapped working on TVs and such, I would have been able to pay my mortgage in ½ year!

There is even ways to have fun with the HV, if you are A) dumb, and B) know what you are doing, like this guy.

https://www.youtube.com/watch?v=Rb6vMgurAH0

[timmy]

It’s very little I’m feeling I don’t think the hv should make it to ground in that way enough to actually feel it. So I guess it’s not possible for any amount of anode voltage making it to ground wouldn’t cause any problems, I feel it could because after all all the circuits wind up at ground. I know I’m grasping at straws at this point but maybe I should try another regulator tube maybe it has a heater short.

[Yamamaya42]

Most likely grounding issue.
The HV cage is screwed to the main chassis, so they are direct connected, the CRT is grounded via aquadag on the outside, normally via a spring touching it, can't be sure about yours not having seen it.
This assembly is normally built into the entire CRT mounting assembly, and grounded at the bottom by a metal strip that touches the main chassis.
If for some reason this does NOT make good contact, then a difference of potential can happen, which can result in unpredictable operation, so usually, when I work on a TV and the chassis is not firmly screwed in the cabinet, I always have a clip lead from the chassis to the CRT mounting assembly for extra safety.