Been after a genuine board of this for a bit now and this one came along. I thought it might be in full working order but once again eBay lets me down.
This one had jailbars through all the main sprites.
More often than not this is a bad ROM and this was ended up being just that.
In the corner of this board there is a bank of 8 MASKROMs that contain the graphics. Unfortunately none of these are in sockets and as I couldn’t really see anything hugely wrong on the scope.
This game doesn’t have a test mode nor does it carry out any RAM/ROM tests on start up so I wrote a little self test program myself in assembly that tested the sprite RAM at location 0x0c2000 – 0x0c3fff in the address map and simply would display a “P” for a pass or “F” for a fail.
This passed no problem so my hope is for one of the ROM’s to be dodgy as opposed to one of those custom chips.
I set about desoldering them one at a time and checking along the way. After the fourth one I found my problem with a bad ROM dump.
My dump is on the right and the MAME set dump is on the left. As you can see, bit 0 is stuck on.
I fitted a socket and reinstalled the ROM but with data line D0 lifted and checked it out with the scope.
On a closer inspection it shows that the logic level isnt dropping below 2v.
The MASKROMs are pin compatible with 27C080 EPROMs of which I have none. I have ordered some so will hopefully receive it early next week
EDIT: EPROM came today, the game is now fully working
2 Responses to “WWF Wrestlefest repair log #1”
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Great job. Thanks for posting your ram test info. Pretty cool!
Thanks. There is some ram clearing routines out of shot but you get the idea. Also it doesn’t deal with the watchdog. I’ll probably write a better test and post it at some point.