Battlezone graphics only drawing for the left 1/2"?

Jeff F

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Battlezone graphics only drawing for the left 1/2"?

Only thing I've done is tested the XY output on a scope to make sure my monitor was working ok and I get the same image on both.

It's not a collapsed vertical line where all the information is being drawn in that line, but it's like the screen is only drawn for about 1/2" from the left and then nothing more across the screen. I only have a few lines being drawn in the left 1/2" vertical strip which looks like the correct lines for what is supposed to be on the screen there... the mountains, horizon line, etc... (hopefully that makes sense)

I'm hopefully going to be able to work on it more tonight but I wanted to see if anyone had any ideas or has run into this before.


It's really a neat problem to me because I know the beam isn't scanning across every horizontal line like a raster display so I'm a bit stumped at why only the left 1/2" would draw. Can't wait to see what causes this. ;)
 
Battlezone (and MH) have a 'window' circuit to limit the region of the screen in which vectors are drawn during certain operations, which effectively does hardware clipping of drawn vectors, saving the math required to clip to the screen in software...

Sounds like yours is acting up...
 
Ah, I see. If I'm following correctly that makes sense. I'll have to look into the "window" circuit to see what's in it and go from there.
 
Been working on the BZ this week and boy was that fun learning about the window circuit. The Vectorlist archives have an awesome amount of information on them... even info. direct from the Battlezone creators which I thought was cooler than crap. :D I found a couple subjects close to my problem(or so I thought) and it made troubleshooting a bit easier.

So... after going through the window circuit a couple times and having a nut of a time understanding just what the heck a LF13201 does... (not sure why I can't wrap my little brain around it... just looks confusing and the datasheet started hurting my head the 4th time through) I found that the output from my X-axis AM6012 was corrupt. The bits going in seem to be decent(or so they look on the scope) but the output is just pegged negative.

I used the Y-axis circuit to help see what I was supposed to get all along the X-axis circuit and it seemed to go good... until I shorted the IO of the Y-axis AM6012(pin 18) with -15v(pin 17) this morning. :(

Good news is the Y-axis now looks exactly like the X-axis so I think a couple AM6012s or DAC312s will move me a step in the right direction.


Now I just have to wait for parts...


And if my "logic" sounds off(ie STUPID) above, my skin is pretty thick so fire away. :beerchug:
 
Yeah... I read it but I was getting confused in a certain section of the schematics... basically on the output of the X-axis DAC there is a LF13201 that confused me... it's the switch with the CENTER trigger.

I stopped by Tim I's up in Fayetteville and he straightened me out in about a minute... it was just me confusing a simple matter. Something I'm pretty good at at times. :D

Thanks again Mark and Tim! :beerchug:
 
Started back working on the Battlezone because I'm burned out of trying to get that second Tempest up. :D

Both the 6012 DACs were bad(one because of me) and then E10, which is a LF13201(or DG201AC), was also bad which caused the screen to offset upwards by 2/3rds(which is about 8v btw).

Now I'm getting the following test screen...
attachment.php


The test screen stays up solid but as soon as I switch back to play the game it basically freaks out. I think the "1" means ROM A3 may be bad but what does the "FF" mean?

I think I'm getting burned out so someone help me fix this Battlezone quick so I can stop and just play. :D

Thanks, :beerchug:
Jeff
 

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FF is a misprint... it should be YF for You're F'd (sorry.... couldn't resist :)
Anyway, it looks like the FF means that all 8 bits of the ROM (A3) are bad, so either the ROM is comletely toast, erased, or the socket is crap and the chip is not getting its power or chip select line.

hope that helps..
/Tim
 
FF is a misprint... it should be YF for You're F'd (sorry.... couldn't resist :)
Anyway, it looks like the FF means that all 8 bits of the ROM (A3) are bad, so either the ROM is comletely toast, erased, or the socket is crap and the chip is not getting its power or chip select line.

hope that helps..
/Tim

I think that Tempest is trying to draw...
YFYFYFYFYFYFYFYFYFYFY
LOLOLOLOLOLOLOLOLOL
YFYFYFYFYFYFYFYFYFYFY
LOLOLOLOLOLOLOLOLOL :D

I'll take a look at A3 tomorrow after work. And good luck on the roadtrip tomorrow! :beerchug:
 
So let's close this trouble ticket out. ;)

A3 was corrupt and after staying up 'til 1:30am last night rebuilding my EPROM burner computer... I ended up burning the bad image to the new EPROM. :D Figured that one out about an hour ago.


So, the picture being displayed on only the left 1/2" of the monitor was a bad 6012 DAC on the X axis circuit. The image being shifted up by about 2/3rds of a screen was a bad LF13201 in the Y axis circuit. A DG201ACJ can be used in place of the LF13201 btw. And finally the garbage on the screen and random reset problem was ROM A3 being corrupt.
 
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Let's add one more to the repair log... :)

A bad Pokey can cause Battlezone to instantly start a game upon power up with the tank repeatedly firing and a loss of joystick control. And the self-test looks good except there are no audible tones when pressing any of the buttons.

This happened after my son and I played about 50 games each. :D Fun, fun, FUN game!
 
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