myPinballs
Member
Hi,
I have a donkey kong (DJR1-01) 2 stack board that i'm trying to get up and running but am having some problems with no video. Blank screen. The board itself is in nice condition with no rust, hacks or bad traces.
Here is what i have confirmed and checked so far.
- Power good to both boards.
- New game roms installed (5B, 5C, 5E)
- New Z80 installed
- Reset line good and solid
- Clock present
- Z80 appears to be running all address lines pulsing , (except for A15 which is high - possible clue to fault?)
- Data lines all pulsing (D0-D7)
- Z80 NMI pin pulsing.
- RD and WR lines are pulsing
- Other control signals pulsing - busak,busrq,mreq,rfsh
Now here's what is odd, the Chip select signals for the roms are not all pulsing. The one to chip 5B is pulsing but the other 2 are high. Also the select pins for ram chips 3B and 4B are high to. The other 4 rams are pulsing.
As i'm looking at the schematic there is some sort of custom memory address chip at location 4D (3192) which looks like a kind of PAL/GAL type custom logic array, but i can't find any info on this or how to check/replace it.
Does anyone have any thoughts on what this could be and if i'm in the right area with this memory address section, or is there something else that could cause these results?
I can't get anything on screen whatsoever, so assume the program is not running.
I have a donkey kong (DJR1-01) 2 stack board that i'm trying to get up and running but am having some problems with no video. Blank screen. The board itself is in nice condition with no rust, hacks or bad traces.
Here is what i have confirmed and checked so far.
- Power good to both boards.
- New game roms installed (5B, 5C, 5E)
- New Z80 installed
- Reset line good and solid
- Clock present
- Z80 appears to be running all address lines pulsing , (except for A15 which is high - possible clue to fault?)
- Data lines all pulsing (D0-D7)
- Z80 NMI pin pulsing.
- RD and WR lines are pulsing
- Other control signals pulsing - busak,busrq,mreq,rfsh
Now here's what is odd, the Chip select signals for the roms are not all pulsing. The one to chip 5B is pulsing but the other 2 are high. Also the select pins for ram chips 3B and 4B are high to. The other 4 rams are pulsing.
As i'm looking at the schematic there is some sort of custom memory address chip at location 4D (3192) which looks like a kind of PAL/GAL type custom logic array, but i can't find any info on this or how to check/replace it.
Does anyone have any thoughts on what this could be and if i'm in the right area with this memory address section, or is there something else that could cause these results?
I can't get anything on screen whatsoever, so assume the program is not running.
