15v2000 - top part of screen missing.

richiewoo

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I have a 15v2000 in an Asteroids Deluxe cocktail that I worked over pretty good.

This thing was working well maybe a month, month and a half ago. Lots of stuff done to it, but either way, it worked the last time I turned it on.

It still works, but the top part of the screen (about 2.5 inches?) is missing. It's not like the screen is squashed up there, it's just dark in that upper half. Otherwise, the monitor is fine.

If I watch the deflection board, I can see the spotkiller light get dim and slightly brighter over and over, like it's pulsing. The size of the darkness at the top changes with the pulsing.

I have no idea and am just pissed because of all the work I put into this thing.

Any suggestions on where to start? The anode wire is not near the yoke, the HV cage has its cover on it. I'm going to go over it one more time, but I'm just too pissed right now.

Any help is appreciated, especially if you have seeen this behavior before!!

Thanks,

~Woo
 
No change

Well, overall the screen gets bigger or smaller, but the top is still cut off. That's a good question though, does the cutoff move with the adjustment? I'll have to check that.

It's just like the monitor isn't drawing on the upper half of the screen. It doesn't seem like a game board problem, plus I sent it to Talon a while back and after the wrok he put in, I don't think this board will ever fail again!

I thought I had seen this before when the anode wire was routed against the tube near the yoke. It's out of the way, so I"m not sure what's going on.

I'll keep digging and maybe post a video. That might help a little.
 
Coming back to this after a break!

I took a long break and have been working on other things. Now it's time to get moving on this again!

The top part of the screen is missing still. I can't tell if it's the monitor or game board.

I've included a pic for reference. I have a video but can't figure out how to upload it!

Lemme know what you think! And thanks!
 

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Working on this again.

I have shelved this for a while, but am back.

Replacing c100 and c101 fixed this, but after about 5-8 hours of playing time, they failed and the issue came back. I have a new bridge rectifier to put in, but want to get a better idea of what might be happening before replacing those caps again (they are expensive!).
 
Thinking about this a bit, I think your issue is in the 500 section, the Y portion of the spotkiller. There aren't many components in that circuit, but I'd check D502, D503, R501, and R521.

What we know is this: When the Y deflection voltage is at its highest, the spotkiller turns on. The 5xx section of the spotkiller takes the Y deflection voltage and rectifies it to -4.7VDC and applies that to the base of Q501. If R521 has become more resistive, or D503 is allowing some voltage to leak through, that will allow the spotkiller to enable.
 
I'll check that tonight

The spotkiller light does come on, and it blinks/pulses with the changes in height of the screen. I'll check those and get back to you.

Thanks man!!
 
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