Dang it all. Tempest monitor woes after rebuild. It worked for a while...

jehuie

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Dang it all. Tempest monitor woes after rebuild. It worked for a while...

Alright, I rebuilt my Tempest K6100 monitor. Full cap kit including lots of extra goodies from Zanen. LV2000. New flyback. Had trouble for a bit and then replaced the zeners on the HV section and it worked beautifully.

For a few days.

Now, sometimes it works beautifully. But more often than not, when I turn it on it plays blind. Powering down repeatedly eventually causes it to work. And once it works, it stays working.

Any thoughts on where to start? I've reflowed solder everywhere I can think of so I don't think it's cold-solder. I've jiggled and shaken things to see if it acts like a loose connection, but nothing.

HELP! And thanks in advance.
 
Is the spot killer LED on? Do you still hear deflection? Do you have HV? Any other details you can give?

DogP
 
Is the spot killer LED on? Do you still hear deflection? Do you have HV? Any other details you can give?

DogP

I have deflection sound. Spot killer is off. But...my B+ has dropped from 180 back down to 24 volts. Which is right where it was before I "fixed" it by replacing the zeners. I can replace them again. They are about 25 cents each so no big deal. But....something is causing them to blow and I don't know where to check.
 
Crickets chirping.....

crickets.jpg


Anyone have any ideas?
 
This is a very quiet and peaceful place. Nobody talking at all. Serene, I would say.

river_peaceful.jpg


I kinda wish someone would break the silence though. :) I'm not sure what to check....
 
Well, I'm still stumped. it's working tonight. I tried fiddling with the cables and wiggling the neck board and generally bumping things around to see if I could get the voltage to drop again but it's determined to work for now.

I've been monitoring the B+ the whole time and I've got a good 180 volts right now. Actually, it starts at about 178 and then every 30 seconds or so creeps up a .1 volts. So now it's up to 184. Not sure if this is normal or a symptom of something.

But I have no idea what might be making the B+ drop so far down when I power up sometimes. Weird and intermittent and hard to trace. Which is probably why nobody else is chiming in.
 
HV shut down? Use HV probe and adjust it a bit lower (edit). Too low of HV could also cause the picture to not display as well.

The shutdown can be touchy.
 
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I think he's saying the HV shutdown may be triggered incorrectly, maybe at too low a voltage. Perhaps by goosing the HV you can make it happen and verify that it is the problem.
 
I think he's saying the HV shutdown may be triggered incorrectly, maybe at too low a voltage. Perhaps by goosing the HV you can make it happen and verify that it is the problem.

Well, I "goosed" it a little and it still plays. Nervous about going to high because I don't want to fry something if the protection circuit doesn't kick in. I don't have a probe so I'm relying on the B+ voltage. Can someone explain to me how this HV protection circuit works? The basic theory behind it? And at what voltage it is supposed to shut down?
 
Ok, I've read up on the HV over voltage protection adjustment procedures and...well....I don't have an HV Trim pot on mine. Nor do I see an LED. So, does this mean that I have an older version that does not have over voltage protection? I read that this was a feature of the later version monitors.
 
Well, then I guess I can eliminate that from the list of possible problems. Which is to bad because it sounded really promising. Any other ideas then?
 
Just worked on a Tempest a couple of days ago where the screen would shrink in half.

Ended up being a bad connector on the top (as the monitor is mounted) "can" transistor on the chassis. No cracks in the solder joint, but the little piece of metal that ran from where the wire mounted (it was the blue one in this case for anyone interested) to the actual leg of the transistor was shot and would open if the machine was tapped or jiggled.

Granted, that was for my problem with the machine. IF the same type of situation happened on another of the transistors, it could cause what you're getting.

What I did was just ran a lead off of a resistor from where the wire attaches to the actual leg of the transistor. Might be worth giving that a shot with yours if all of the wires to the transistors are checking out good. It'll be a PITA later when/if you do a rebuild on the monitor... but might be worth it for now. If you have one that's open, it could still test good with a multimeter because the pressure you put on it when you test it is closing the connection.

Anywho, that's all I can think of off the top of my head. YMMV, own risk, etc etc etc.
 
Thanks. I'll double check that. I've replaced all those "can" transistors and they seem to all be solid as far as I can tell. And no amount of shaking and bumping can cause it to misbehave if it fires up ok the first time. But on alterting start-ups it will not work and no about of cajoling will get it to work either.

I'm ready to go try to buy a whole 'nother HV unit somewhere. Intermittent problems suck.
 
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