Sega-Naomi

Hi,







I'm trying to fix an odd problem with a Sega Rally 1 twin.



Static graphics are fine (ram tests OK), but on one of the machines the background is flashing triangles, on the other the bit-maps have vanished????



I have swapped and replaced boards on machine one, until only the ROM boards could be the fault - I have a replacement board (supposedly SR1) but it just produces a random hash and does not boot. There's not much on these boards to go wrong; do the ROMs lose data?







Bill

BillTodd2011 wrote:Hi,







I'm trying to fix an odd problem with a Sega Rally 1 twin.



Static graphics are fine (ram tests OK), but on one of the machines the background is flashing triangles, on the other the bit-maps have vanished????



I have swapped and replaced boards on machine one, until only the ROM boards could be the fault - I have a replacement board (supposedly SR1) but it just produces a random hash and does not boot there's not much on these boards to go wrong, do the ROMs lose data?







Bill

I've heard of some ROMs which have issue s known as bit-rotting (or something similar named). It's possibly, but unlikely to happen.

NaokiS wrote:


I've heard of some ROMs which have issues known as bit-rotting (or something similar named). It's possibly, but unlikely to happen.

Well that's some reassurance



Are there any circuit diagrams around for these old machines? (I'm quite used to faulting find to the component level on digital equipment )



Bill

Well, I've found that some of the ROMs HAVE indeed lost their memory !



I've fixed the second machine of the pair (bit maps missing) by just swapping the six texture ROMs from one board to another.



And, by swapping ROM boards between machines, I've narrowed the machine one fault to the ROM board and/or other ROMs.



I have a spare ROM board that unfortunately appears to have the same or similar fault as the faulty one so ATM I'm stuck (I may try swapping the whole chip set with a Virtua Fighter game that is currently out of action with a dead monitor (anyone have circuit diagrams for 29" Nanao fixed frequency monitors).



So, If you have a Sega Rally 1 I strongly suggest that you copy the ROMs to a PC before they start failing!



Bill

i have the same problem with the triangles, it's turn me crazy, the rom board is a little corroded with the air of the sea, i will take the sockets out and put new ones, i have a lot of maskrom bad, i have an eprom programmer, that's not a problem i have 27c160 blank eproms too, tell me your news, sorry for the english, i'm form uruguay.

i have a video of the problem, see it!!!!

http://www.youtube.com/watch?v=APzNcWyXdoU

Well, I'm going to have to throw the towel in - I can't fix this sega rally twin.



Anyone know what a half working SRT would be worth these days?

i have a working sr1 pcb if you are interested.

Thanks STV but the owner has now decided he need the room for a bar, so the SRT going to the breakers.



Bill

Breakers? Whats that, skips? Dump?