ArcadeCollecting.com
Welcome, Guest. Please login or register.
December 15, 2019, 02:32:24 PM

Login with username, password and session length
Search:     Advanced search
Yay, a message board!
319 Posts in 114 Topics by 43 Members
Latest Member: deejaymc
* Home Help Search Login Register
+  ArcadeCollecting.com
|-+  General Category
| |-+  Repair logs
| | |-+  Pang (bootleg)
« previous next »
Pages: [1] Print
Author Topic: Pang (bootleg)  (Read 2517 times)
tim
Administrator
Full Member
*****
Posts: 166


View Profile
« on: November 20, 2005, 04:57:22 PM »

Symptom
Screen full of 0's, random flickery garbage, no boot.

Tests
Hooked up logic analyzer. Found the main CPU was in an endless loop at address 81F6. The instruction
at 81F6 is a Jump to 81F6. Hmmmm. Loaded a debug version of MAME and stepped through the code. Found it never
got to 81F6. It did a bunch of RAM tests first and never got to that address if the RAM passed it's tests...
That must mean the RAM wasn't passing. Tested the pair of 6116's with my EPROM programmer. They passed.
Powered on the board with one ROM pulled off and got the same screen, but with hosed colors. These must be the color RAMs. Swapped
the 6264 next to the program ROMs with another. No change. That left a 2018 next to the graphics ROMs and
the 2018 next to the sound ROM. Suspected 2018's are compatibile with 6116's, so popped it into my EPROM
programmer and tested it as a 6116. It passed. For kicks I stuck one of the 6116 color RAMs into the socket
and powered up. It booted but with hosed colors (like I expected). Stuck the 2018 in the color RAM socket and
it booted perfectly. Swapped the 2018 back where it came from and it booted, reset and gave a RAM error. Put
the 6116 back in the 2018 socket and it booted fine. WTH? I didn't really do anything. Oh well. Maybe a flaky socket. If it works, don't fix it.

Symptom
No sound

Tests
Touching around the sound section made random garbage sounds come out of the speaker -- amp must be working.
Swapped a 6116 color RAM with the 2018 next to the sound ROM. No change. Close inspection revealed a little
wierd blue box with a leg not making contact to the solder pad. A gentle pull on the thingy and it came right
off the board, and the leg fell off.

Fix
Dropped a big blob of solder on the little metal nub that was left
and used that to make contact to the solder pad. Powered up, coined up, got sound.
Logged
Pages: [1] Print 
« previous next »
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.19 | SMF © 2013, Simple Machines Valid XHTML 1.0! Valid CSS!