Welcome, Guest. Please login or register.
February 27, 2020, 07:51:05 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
|-+  General Category
| |-+  Repair logs
| | |-+  Mutant Night (bootleg)
« previous next »
Pages: [1] Print
Author Topic: Mutant Night (bootleg)  (Read 2583 times)
Full Member
Posts: 166

View Profile
« on: November 20, 2005, 05:00:39 PM »

Dead. Missing all EPROMs.

Burned a set of ROMs from MAME, matching ROM numbers to socket numbers. No workie.
Reset over and over. Read existing masked ROMs and ran through ROMident. From comparing the numbers on the bootleg to the naming reported by ROMident, I deduced that the bootleg has the socket numbers flipped around from the original. 13=1, 1=13, 12=2, 2=12, etc.

Plugged the ROMs in the correct order and game booted with ROM error 5. Reburned 5th ROM over from the CPU (not the one labeled "5") and game passes self tests, but...

Sprites missing every other vertical line.

Self test reported all RAM as good, so suspect surrounding TTL chips.
Poking around at all the chips with the logic probe, found one 74245 (buffer) whose outputs didn't seem to match
the inputs. Pulling an output low caused the missing sprite lines to fill in solid. Gotta be this chip! Desoldered
the chip and tested it. It's good. Bleh. Socketed it and tried another 74245. No change. Probed pins with nothing
in the socket and found pin 1 floating. Pin 1 = DIR. Replaced 74245 and jumpered over to a nearby 74245's DIR pin.
It's good!!

Inspected bottom of PCB and found trace broken from DIR pin to ground. Soldered a jumper wire.
« Last Edit: November 20, 2005, 10:45:20 PM by tim » 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!