U3100 Troubles

[Kevin Mullins]

Picked up a Touchmaster Infinity from an auction and all seemed good. But after a few power ups it started to show signs of a monitor issue and sure enough....now it won't come up. (plays blind)
Of course trying to get this out for Christmas so I'm on crunch time. So was hoping to get any quick or handy tips before I dive into it.

Has a P786 main chassis and P831 Neck board (U3100).
WGT1431

Monitor seems to power up, HV etc.
"Briefly" there appears to be a horizontal collapse line showing then shows nothing.

Gonna check caps, solder joints and the usual once I get it apart....
 
Just wondering if anyone has an immediate pointer to give as I'm not familiar with this particular chassis. (in case there may be an IC involved or something)

[grantspain]

we had a load of touchmaster in the u.k with this monitor-i had loads do this and it was a cap-i don't remember which but i am sure it was something like a 1uf

[grantspain]

also the vert frame ic may have popped

[Kevin Mullins]

Thanks grant .... I'll poke around with some caps.
Which is kinda how it acted before it just completely quit. The "would sometimes work" and then just died altogether effect.

As for the vertical IC question....
It definitely would show a sharp vertical line briefly and then quickly go away. Which makes me think it's more of a horizontal issue. (horizontal mounted, vertical line)

If you can think of a specific that would be a time saver.
And of course ordering anything is out of the question for now which sucks. 

[grantspain]

sorry misread-fkyback could be the issue here

[Kevin Mullins]

fkyback could be the issue here

Shhhh ..... that's just not nice.   

This thing is just acting funny.
I fiddle fart around with it looking it over real good, nothing notable seen like solder joints and such. Changed one cap (C601) just because it was mentioned in the troubleshooting guide a couple times for various reasons, no change.
Then all of a sudden it starts working again. 
Slapped it back together..... and it quits again.
So there's definitely something bad or at least on it's way to be bad.

Not sure about the flyback.
I do have a junk chassis laying around I could try swapping that out.
But startup sounds pretty normal. Good HV crackle and whatnot.
Of course that means nothing as far as any secondary voltages go.

[grantspain]

you will need to check everything from pin 10 of the flyback

[Kevin Mullins]

Will do ...

It's being just flaky enough to be hard to pinpoint.
Again, all of a sudden it wants to work.
Figure I would check the video output from the motherboard too while it's out just to eliminate that.

[Kevin Mullins]

Ya know... the darn thing started working fine again after fiddling with it some more.
Played on it all night and part of today so far without a hitch.
 
So I'm gonna plan on doing a complete cap kit on it and see how it behaves for awhile.

[grantspain]

perhaps you have a very fine crack on a trace

[Kevin Mullins]

Quite possible.
Intermittent for sure.
Because otherwise the picture is beautiful and rock solid.

Once the holiday has calmed down I'll probably tear it down again and take a closer look and cap it. Then I don't have to rush anything on it.

[Kevin Mullins]

Bit off topic.... but did you ever have trouble with hardrive hum coming through the speaker?
This one seems a bit annoying because it's so pronounced.

[grantspain]

are sure its hdd or some kind of feedback
i don't remember having this problem and we had over 200 megatouch and touchmaster

[Kevin Mullins]

The noise that comes through the speaker certainly seems to be consistent with the hdd hum/buzz/spinup. Hadn't really poked around with that issue much as it's being played most of the time right now. Was going to check it out when I have it apart again.
It's not terrible, but noticeable when the volume is turned down.

[grantspain]

sounds like some kind of feedback through the +12 line-maybe a bad cap in the psu or sound amp circuit
i do know that these had loads of ferrite cores around cables to act as suppression,maybe one or two are missing

[Kevin Mullins]

I was actually thinking of playing with the idea of putting a core around the speaker leads to see if it made any difference when I read your post. Needless to say I tried it and it had no effect on the noise. But... while it was running I unplugged the power from the hardrive and the noise went away. So I looked at the power supply and noticed the fan wasn't running. I had a new spare here so I swapped it out. Works fine, but noise still there. I may check the caps on the motherboard itself next. You may be right on the +12v feedback of sorts from somewhere.
The monitor started flaking out again, which made for a good time to dig into all this again.
This time I had another monitor ready to hook up to it and see what was going on. At first it seemed to be a motherboard issue because when the original monitor went blank I hooked the other up and it too was blank. But come to find out it was just due to a random lockup up the system. Next time it went blank I hooked the other up and the other montior came up fine. So I then looked closer at the original monitor and noticed it had no heater glow at all, no raster when turning the screen voltage up, etc. Not just a horizontal failure. So it was like it was firing up and then immediately shutting down. Later on it came up and worked great for several hours.
Still gonna plan on capping it completely once I get a list together as I haven't seen any "kits" for it yet. Will probably cap the motherboard as well.

Then I also came across a bulletin on the ArcArc site that I may check into and try. (see attached) Which could possibly be what it's doing according to the symptoms.
Ever seen that additional cap put on any of these monitors? (worth a shot)

EDIT: Just fired it up again this morning and it's working fine again. 
Where's the "pulling your hair out" icon when ya need it.

[grantspain]

i can't remember rightly where the cap i had problems with was located as it is over 5 years ago
i would cap the lot and do that update as a matter of course

[Kevin Mullins]

Jeez..... there's like 50 electrolytic caps on this thing. 
I guess it'll give me a reason to order a bunch to have on hand.

Made up a quick list in case anyone else goes looking for one. (attached)

[grantspain]

only change the ones in the relevant circuits,psu and deflection