battle zone monitor issue but not monitor?

vincent

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When I power up my battle zone I get half to 3/4 of a picture then it fades left to dark. Plays blind and everything else works. Turn up the brightness and all is there with vector tracing lines of course. Is this a power supply issue or my main board? It does the same thing with the monitor out of my red barron. I am a novice at this help please.
 
When I power up my battle zone I get half to 3/4 of a picture then it fades left to dark. Plays blind and everything else works. Turn up the brightness and all is there with vector tracing lines of course. Is this a power supply issue or my main board? It does the same thing with the monitor out of my red barron. I am a novice at this help please.


Wiggle the video cable connector at the monitor and reseat the video connection at the main board also. The X & Y is obviously working by the Z (brightness signal) might have a loose terminal. If wiggling the connector works a bit, even if it is intermittently, try resoldering the header pins on the bottom of the PCB. Sometimes the solder cracks in a thin ring around the pin. This is a common failure because of people swapping boards and monitors and pluggin/unplugging the video connector many times over the life of the machine. Resoldering the pins can cure this. I usually also replace the header and the connector terminals with new parts so that there's good new plating on the connection surfaces.
 
Tried that but no luck. I don't think it is a lose connection. when you first turn it on the image comes up on half the monitor and then very delibertly goes away like pulling a blind over a window. Seems like something at the component level that just doesn't have enough to keep going and just gives up. Power the machine off for 10 or 15 seconds and turn it back on and it will do it again.
 
Yank the deflection board - resolder all the molex header pins. Also check all the fuses as well as the two big resistors (R100 and R101).

You may also want to check the fuses in the power brick and clean up or replace the fuse holders. The heater voltage is probably suffering, and for vectors it comes directly from the power brick.
 
Tried that but no luck. I don't think it is a lose connection. when you first turn it on the image comes up on half the monitor and then very delibertly goes away like pulling a blind over a window. Seems like something at the component level that just doesn't have enough to keep going and just gives up. Power the machine off for 10 or 15 seconds and turn it back on and it will do it again.

This is indicative of a inter-connect cable that is not fully seated between the cpu and the aux board. It is also possible that the headers for the inter-connect cable have cold solder joints, and should be reflowed.
 
I've got a Red Baron boardset that does this exact same thing (along with some other issues). I have yet to figure out the cause. I can tell you my issue lies on the AVG board.

Edward
 
I've got a Red Baron boardset that does this exact same thing (along with some other issues). I have yet to figure out the cause. I can tell you my issue lies on the AVG board.

Edward

What do you get when you hook it up to an O-scope Edward?
 
it sounds like its the z-channel on the board....

Doesnt B-zone have comparators on the output to clip when the scanning goes out of range?

Look at the op-amps/comparators to see if they are getting hot. Since it fades out over time, I'd suspect heat...
 
What do you get when you hook it up to an O-scope Edward?

You know, I haven't done that yet. It was such a freaking looking problem, and I was already pissed off at the damn thing....it just got tossed to the side "for another day".

Mine is also watchdogging....about every two seconds. So, in demo made it "looks" fine (because it's constantly resetting. In test mode it doesn't watchdog. So, I can watch the screen slowly wipe away. It starts at one corner and slowly wipes to the opposite corner. Just as the OP said....it's like a blind being pulled. It takes about ten seconds for my screen to be "wiped" clean. Flick it out of test mode and back into test mode....I can watch it happen again....pretty sure it's not heat related.

Edward
 
You know, I haven't done that yet. It was such a freaking looking problem, and I was already pissed off at the damn thing....it just got tossed to the side "for another day".

Mine is also watchdogging....about every two seconds. So, in demo made it "looks" fine (because it's constantly resetting. In test mode it doesn't watchdog. So, I can watch the screen slowly wipe away. It starts at one corner and slowly wipes to the opposite corner. Just as the OP said....it's like a blind being pulled. It takes about ten seconds for my screen to be "wiped" clean. Flick it out of test mode and back into test mode....I can watch it happen again....pretty sure it's not heat related.

Edward

I would have to say... hook it up to an O-scope and see what you get. If it comes up fine on the scope, it is a monitor issue. If it doesn't, it is definitely a boardset issue. I have experienced exactly what both you and the OP have described, and magically some how the interconnect cable wasn't fully seated.
 
I have solved some weird seemingly monitor issues on atari vector games by replacing the "Big Blue" capacitor on the main power supply. Not a monitor issue at all.
 
Someone already said it, but it does sound like a z problem. The z increases, or decreases the brightness of the lines basically. It does seem strange that it would only do this on half the monitor.

I might start with q7,8,9 and then work your way back from there.
 
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