SW/ESB kit ROM error at 1F

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OK, I'm really stuck now.

I've so far installed 2 SW/ESB kits on two board sets without any problems at all. Both are still working beautifully after about a year.

Now, the third is giving me serious headaches.

When I installed it the first time, it was constantly resetting. When I switched it to test-mode there was an error at ROM 1F. Pretty logical, as you have to remove all the original ROMs and the kit get's inserted at ROM 1F (as well as to the CPU and NOVRAM sockets).

Since then I've tried everything to find the problem. I've installed the same kit on my spare PCB set (which is not in the best physical condition, but works) and it worked fine.
So you'd think it would be a board problem on the original set BUT that one is working fine as long as I use it in factory original set-up.

So if the PCB is working fine without the kit, and if the kit works fine on another PCB, where could the problem be ?

I figured it might be the sockets. So I replaced the CPU, NOVRAM end 1F EPROM sockets, but the result is still the same ROM error at 1F.

(Does anybody know what the extra letters behind the error message indicate by the way, the documentation seems to not mention it. Looks like an address ?)

So, now I'm lost. I measured all adress and data lines from the buffers to the CPU and to the EPROM socket, check outed the buffers themselves (compared to my spare board) and everything seems OK.

Could it be that the kit has some more requirements for certain levels and that f.i. the buffers are managing the normal EPROMs but not the kit ?

Any help very welcome !!
 
The extra letters are the checksum...

The kits require far less drive from the buffers than the original game, since there's only 1-2 roms where there used to be 5...

Is 1F the only error it's giving? I can't remember if it'll pick off more than one bad ROM...
 
Yes, only 1F. That the buffers are less loaded makes sense. So I assume we can rule this out then.

Would the checksum give any extra info ?

So how does this test-mode actually work. Since the program IS in the program ROMs, how does the PCB manage to run the test program ?

I assume it calculates a checksum from each ROM that it compares to a table. Obviously the conclusions of the checksum test is correct, since the program seems to crash and probable make the watch-dog reset the board (and that keeps going on when not in test-mode).

By the way, thanks for chiming in Mark, it's good to have the creator of the kits on board here ;) I earlier sent an e-mail because I thought I had tackled the issue with the sockets, but it turned out not to be the problem regretfully. I'm completely baffled by this...
 
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If it's any help the full error is PROGRAM ROMO AT 1F DBE8.

My next step is a 1:1 compare check between the spare CPU board (that works with the kit) and my friend's board (the one with the problem).....

If there's any points I should check with a scope please let me know...
 
All my SW debug info's on my old computer that's not yet set up at the new house (no cable/net there anyway)... I can't remember offhand what the checksum is supposed to be, but I think it's just a big 16-bit add...
 
The re-booting sound is exactly the same but I never get anything on-screen from the start.

Did you run it in test-mode when that happened and if so what did it say ?
 
Well, I have it set to boot Star Wars so that's why I had the SW screen. I reseated the daughter board (or that ROM that's on it) and it worked like a champ. That was Spaeth's recommendation when I was having that issue.
 
The re-booting sound is exactly the same but I never get anything on-screen from the start.

Did you run it in test-mode when that happened and if so what did it say ?


Also, when I ran it in test mode I did get an error or two. When I re-sat stuff everything went away.
 
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