Pang Color Problems

Stoog

Member
Joined
Apr 28, 2014
Messages
977
Reaction score
6
Location
Australia, NSW, Australia
Hey everyone

Decided to have a look at this Pang PCB i had for awhile now. Originally when i got it the battery died and did the battery removal/mod but couldn't get it to boot/run.

Anyway today i checked over my work couldn't see any problems the new program roms were fine but i tired a different brand of eprom and to my suprise the game booted up :) The ones i used first time were Intel branded now i am using AMD branded. Not sure if one of the Intel eproms i used was faulty when under board conditions or what.

Anyway now i am onto this problem with the color issue

I started at 8C/9C and socket/replaced those 2 rams which were the common to fail Sony CXK branded rams no change in fault. Background is displayed correctly but the color/shading is incorrect. The only part that looks fine is the part of the title screen and the bouncing bubbles

Tracking back from those rams i couldn't find any TTL based issues but i got to the 86S100 which i have a bad feeling is faulty :(

Other then that game runs/plays fine just all colors are really wrong

Anyone come across one of these that have been faulty before?
 

Attachments

  • 2016-10-18 17.06.55.jpg
    2016-10-18 17.06.55.jpg
    200.2 KB · Views: 22
  • 2016-10-18 17.06.36.jpg
    2016-10-18 17.06.36.jpg
    200.2 KB · Views: 27
  • 2016-10-18 17.06.10.jpg
    2016-10-18 17.06.10.jpg
    198.3 KB · Views: 24
  • 2016-10-18 17.05.52.jpg
    2016-10-18 17.05.52.jpg
    195.1 KB · Views: 13
Question

This PCB has a sticker on the bottom stating it once was a super pang but checking all eproms on PCB comes up as a standard Pang/Buster Bros

I take it both games can be used?
 
Last edited:
It's clearly not a color issue.If it was so, also the color of the bouncing balls would be bad.Text and foregrounds have missing layers, you can clearly see the blocky graphics sign that data are missing.

P.S.
Pang and Super Pang run on same hardware
 
Last edited:
Maybe more than foregrounds , it's the backgrounds to be bad.Anyway, try to load some dummy files into MAME instead of GFX ROMs and see if you can reproduce the issue.
 
ahh good idea ill do that see how i go

that 86s100 does run into the gfx data lines which makes me think thats the issue i can get one if needed but really hope its not
 
Try first to understand if data from EPROMs are good.The 86S100 is nothing more than a buffer (like a 74LS245)
 
Well no joy on it yet went over the GFX areas using a working PCB to match the color/gfx issue PCB just in case i may have missed somthing and still can't find anything wrong on the scope so sadly i am at a point now where i am not sure really what else to look at/for.

Tried to remake the fault in mame but had no joy even getting close with it.

The only thing that comes to mind is the 2 rams i changed were 35ns i replaced with 90ns which are faster the only thing that comes to mind is maybe those rams are too fast? ive seen this before along time ago on a Cabal it didn't like a faster ram fitted in the GFX area
 
Last edited:
The only thing that comes to mind is the 2 rams i changed were 35ns i replaced with 90ns which are faster the only thing that comes to mind is maybe those rams are too fast? ive seen this before along time ago on a Cabal it didn't like a faster ram fitted in the GFX area

Wrong.The less is the number in ns , the faster is the access time so 90ns is slower than 35ns.
Anyway, palette circuitry requires precise timing so you have always to replace related RAMs with same factory part (same or faster access speed, I mean).
 
Last edited:
Woohoo i fixed it :)

Was the incorrect speed ram all along i fitted to the color ram. So if anyone in the future has a color issue don't use 90ns it doesn't work originally fitted was 35ns i fitted a pair of 45ns and works great i found on a scrap reason for the 90 was thats what i had in my parts tray at the time

Job Done
 
Last edited:
Back
Top Bottom