Solved Mr. Do! MRD-1102 PCB - No sprites

[Georgian2]

Hello,

Here I have another tough one. After getting rid of some stuck blue horizontal lines (bad LS273 on S9), I can't find any other fault. All GFX roms are fine. 3 of the 4 CPU roms dosen't match any romset. I guess this is because there is no PAL at J2 so must be some hacked roms. I did put an diagnostics ROM in and it shows all rams are fine.
Can anybody do some measurements on theyrs?
OB1-OB4 outputs on G10 (LS157) are LOW. The IC is good and if out of socket, everythis is floating, so no stuck inputs. There is acitvity when sprites should be displayd.
There are no pull-ups on the PROMS (E10 and J10) but they are tri-state so it shouldn't matter there is activity on all the outputs.

Any help is appreciated.

Thanks.

https://www.arcade-museum.com/manuals-videogames/M/MrDo.pdf


Got it... it was the two 2148 SRAMs at F8 and G8. I tought that I could get away using 2114 instead. Pulled 2 from other working PCB and it restored all the sprites... Good one.

 

[sukhbir]

Hello,

Here I have another tough one. After getting rid of some stuck blue horizontal lines (bad LS273 on S9), I can't find any other fault. All GFX roms are fine. 3 of the 4 CPU roms dosen't match any romset. I guess this is because there is no PAL at J2 so must be some hacked roms. I did put an diagnostics ROM in and it shows all rams are fine.
Can anybody do some measurements on theyrs?
OB1-OB4 outputs on G10 (LS157) are LOW. The IC is good and if out of socket, everythis is floating, so no stuck inputs. There is acitvity when sprites should be displayd.
There are no pull-ups on the PROMS (E10 and J10) but they are tri-state so it shouldn't matter there is activity on all the outputs.

Any help is appreciated.

Thanks.

https://www.arcade-museum.com/manuals-videogames/M/MrDo.pdf


Got it... it was the two 2148 SRAMs at F8 and G8. I tought that I could get away using 2114 instead. Pulled 2 from other working PCB and it restored all the sprites... Good one.

The 2148 srams used on Mr do! Have very fast access time about 50ns,the 2114 type are much slower.

 

[Georgian2]

The 2148 srams used on Mr do! Have very fast access time about 50ns,the 2114 type are much slower.

I know. These two were the only two socketed. Other 4 are 2114 soldered in. I thought at first I'd just swap them for 2114. I didn't see any difference so the originals 2148 must be good, right? So I put them back, lol. Only now I thought let's put some known good ones in...
Yeah... one more game saved 🥳

 

[favouredson]

Hello,
3 of the 4 CPU roms dosen't match any romset. I guess this is because there is no PAL at J2 so must be some hacked roms.

The protection is on ROM1 @ A4.

From highwayman back in the day:

protection:
$0494 ld a,($9803) [3A 03 98]
replace with:
$0494 nop [00]
$0495 nop [00]
$0496 ld a,(hl) [7E]

prototype uses address $04a4