- Joined
- Jul 21, 2011
- Messages
- 457
Hi Guys -
Quite a technical one this.
When powering up my BTTF, ALL the coils fire momentarily on switch on. Having investigated the whole blanking circuit, and changing everything I thought could effect it, I ended up swapping out the CPU as it was still the same.
Put a new CPU in the game, and it happened again. After a day of head scratching, I worked out that the CPU IC seemed to be at fault (as putting another IC into the program slot made the board boot correctly with no coils firing).
Yes, I have checked the link!
I had combined the BTTF rom into one 512k IC, and used the J5 link as I always do. Saves messing about with two ICs. To double check, I downloaded the files from IPDB again, for the two separate 256mb ICs, and rejumpered the board to J4. Still the same!
I eventually removed the CPU to the bench, to avoid geting any issues from other boards and the wiring etc.
When using other game IC's (tried GnR and LW3), the game boots up correctly with no coils firing. When using the BTTF roms (either the 512k or 2x 256), the coils fire on startup. I assume theres a bug in the IPDB rom images! Can anyone help here, or confirm?
One thing I have noticed is that when you start the board up with GnR or LW3 roms, the PIA led and the 5V led lights up, and then after a second or so, the PIA light goes out and the blanking light comes on. This is normal of course.
When you use the BTTF roms, there doesn't seem to be a second or so delay between the PIA light going off, and the blanking light coming on. It does it so quick, it seems to be beating the timing of the blanking circuit.
Ideas??
Better still, has anyone got a image from a BTTF I could have please? Seems the IPDB ones are corrupt. I've tried re-burning them to different ICs, with the same results.
Quite a technical one this.
When powering up my BTTF, ALL the coils fire momentarily on switch on. Having investigated the whole blanking circuit, and changing everything I thought could effect it, I ended up swapping out the CPU as it was still the same.
Put a new CPU in the game, and it happened again. After a day of head scratching, I worked out that the CPU IC seemed to be at fault (as putting another IC into the program slot made the board boot correctly with no coils firing).
Yes, I have checked the link!
I had combined the BTTF rom into one 512k IC, and used the J5 link as I always do. Saves messing about with two ICs. To double check, I downloaded the files from IPDB again, for the two separate 256mb ICs, and rejumpered the board to J4. Still the same!
I eventually removed the CPU to the bench, to avoid geting any issues from other boards and the wiring etc.
When using other game IC's (tried GnR and LW3), the game boots up correctly with no coils firing. When using the BTTF roms (either the 512k or 2x 256), the coils fire on startup. I assume theres a bug in the IPDB rom images! Can anyone help here, or confirm?
One thing I have noticed is that when you start the board up with GnR or LW3 roms, the PIA led and the 5V led lights up, and then after a second or so, the PIA light goes out and the blanking light comes on. This is normal of course.
When you use the BTTF roms, there doesn't seem to be a second or so delay between the PIA light going off, and the blanking light coming on. It does it so quick, it seems to be beating the timing of the blanking circuit.
Ideas??
Better still, has anyone got a image from a BTTF I could have please? Seems the IPDB ones are corrupt. I've tried re-burning them to different ICs, with the same results.
