Dig Dug Board help

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OK, hopefully I have this in the right spot now :)

Hi all,

I've been trying to fire up my dig dug board and it has some issues....

I have rebuilt the ARII, then measured the voltages.
The 5v line was pretty spot on 5v and the other was 11.7v or something like that.
I measured at the 5v line at the connector, test points and the IC's and am getting a solid 5v.
The connector also looks good.

The first picture is what I'm getting on screen and the second picture is what I get when I pull the Z80 out located at 6K.
Dig Dug has 3x Z80's, so I did try all 3 in all 3 sockets to see if I could get something to change, but nothing.

I've removed, cleaned and reseated all socketed chips, but there was no change.

Has anyone seen these screens before ??

OH and don't mind the "checked & ready that's written on the screen, it was like that when I bought it and haven't cleaned off yet.
 

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Apparently it's not booting at all. Your trick of swapping Z80s around is akin to moving a flat tire from the front to the back. Do you have any other known good Z80s? Static garbage is usually a sign of a dead CPU.
 
Apparently it's not booting at all. Your trick of swapping Z80s around is akin to moving a flat tire from the front to the back. Do you have any other known good Z80s? Static garbage is usually a sign of a dead CPU.

Should do, I have plenty of different boards here..
Might try the 3x Z80's in a known working board as well, one that only requires 1x Z80.
 
I like that flat tire analogy. lol

voltage spikes on these are becoming scarily more common. so who knows. make sure they're not plugged in backwards too. they take +5 in a weird middlish pin instead of the corner, so I'm sure that'll pop something.
 
OK,
I've tested all 3 Z80's in a bootleg galaga board and all tested good.
Which is not good ! LOL
As now its got to be something else....
 
I have logic probe on the way, just hoping to have some sort of idea where to start poking around ??
 
You mentioned rebuilding the AR2, but did you change big blue? Your 11.7VDC should be around 10.6VDC. Those big blue capacitors are notorious for causing all kinds of ruckus. I have no vested interest, but I've bought a bunch of stuff from https://www.arcadepartsandrepair.com lately and they're pretty awesome. They have freshly manufactured "big blue" caps for $15.00. Even if it doesn't fix your problem, it can't hurt to change and at least you can rule it out.
 
I have a fully working centipede here, maybe I can swap out the power bricks and see if there is any difference...
 
Don't know if this helps but I had a DD that booted to a static, random screen similar to yours. It turned out to be a bad 2016 static RAM.
 
Don't know if this helps but I had a DD that booted to a static, random screen similar to yours. It turned out to be a bad 2016 static RAM.

Thanks, I will check them out :)

Hopefully I can find one to piggyback..
 
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You mentioned rebuilding the AR2, but did you change big blue? Your 11.7VDC should be around 10.6VDC. Those big blue capacitors are notorious for causing all kinds of ruckus. I have no vested interest, but I've bought a bunch of stuff from https://www.arcadepartsandrepair.com lately and they're pretty awesome. They have freshly manufactured "big blue" caps for $15.00. Even if it doesn't fix your problem, it can't hurt to change and at least you can rule it out.

I think you are referring to the unregulated 10.3 vdc that is used on 5v side of AR2 for the +5v. Op is referring to the +12v regulated on the other side and +11.7vdc is fine at the board.

I have read usually logic chips have operating range of +/- 5% which is @ 11.5 - 12.5 on the +12 and 4.75 - 5.25 on the +5.

There are two board types for dig dug. One has z80's on opposite side so you might want to verify voltage at the chip. Also check the reset pins of the z80s.
 
My board has the Z80's in the middle of the board.

My board doesn't seem to have any 2016 RAM chips, but it does have 2114's....

I had a known working 2114 ram chip, so I piggybacked all the 2114's on the board, but got nothing different.

I then started pulling ROM chips off the board one by one and started the game between each time and I did get a change with ROM's 101 & 104.

The first attached picture was when ROM 101 was removed.
Other picture is of when ROM 104 was removed, it was rolling though those screens.
 
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Hmmm.........

For some reason I couldn't attach pictures to my above post ??
 
I received my GQ-4x4 programmer and this was the first job I wanted to do.....
Test all the Dig Dug ROM's ! :)

After testing them all, I found 1x bad one, by checking with Rom Ident.
The bad one was 115 located at 10C/D.

If any of you have a Dig Dug, can anyone be able to pull that ROM out of the board and see what it does ?
Will be interesting if it comes up the same as mine.

I haven't yet received my eraser and I haven't any blank chips here yet.
 
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