Testing a bad ROM chip?

[guitarzombie]

I just bought Super Turrican PAL B. First things first my lockout chip was disabled. So I get the game, clean it. Nothing. Cleaned it MORE, nothing. Even cleaned the inside of my NES again. Nothing.

Now before I made a repro of the game for myself so I had another TSROM board laying around. I removed the EPROMs on my WORKING repro and put in the Mask ROMs from the legit cart. Nothing.

What gives? Could there be a static electricity thing that happened during shipping? How can I definitively test if the PRG is bad?

I got a couple of sockets and im thinking about possibly making an adapter for a 28-DIP 128K mask rom and see if my willem will read it.

Short version:

Game doesnt boot.
-Lockout chip disabled
-Cleaned
-Moved MASK ROMs to working board.

[lidnariq]

The 28-pin DIP Mask ROM is a JEDEC standard (with part numbers something like 23c1001), so you might see if your programmer just happens to support it.
Even failing that, you should still be able to read the first half by pretending it's a 27c512.

[guitarzombie]

The 28-pin DIP Mask ROM is a JEDEC standard (with part numbers something like 23c1001), so you might see if your programmer just happens to support it.
Even failing that, you should still be able to read the first half by pretending it's a 27c512.

I never thought about that (using a 64k shell). My device also doesnt have a 23, starts 24 and up.

BUT I figured it out.

I realized since I burn 301s, I should be able to use my 301 adapter I made, but just give 5v to Mask rom 28 via the willems hole 32.

I used a 128k Mask Rom Super Jeopardy to test it. Eureka it worked! I was able to read and verify it against the nes file I split.

Popped in Turrican... all FFs... with a few 7Fs in the last half

How does this happen? I dont think I ever had a game except one just NOT work? Static electricity?

[l_oliveira]

Sounds like the rom just "died"... A common cause is oxidization on the bonding wires. That's why some people who repair arcade boards dislike Fujitsu TTL chips so much...

I have a Hitachi made mask rom I replaced from a Parodius cartridge which has odd random patterns at very specific positions of memory. That hint addressing errors due to problems on the die (the error pattern is way too regular to be due to bonding issues).