the simpsons

[VectorGlow]

You could try a piggy-back of a known good EPROM (of the right type) on the remaining mask ROM (remember that there's only two that hold the sound samples and one has already been replaced by an EPROM). Not sure if piggy-backing would make any difference mind you.

Here's what I would personally do:

a) Verify the EPROM at 6G (that's the main Z80 code - I would imagine that's fine or you wouldn't get any sound at all!)

b) Check if the address and data lines are active on the mask ROM and the EPROM that has replaced the mask ROM at location 1D and 1F

c) Verify the contents of the 'new' EPROM at location 1F

d) If all the above looks okay, then you could try a piggy-back or, better still, carefully remove the mask ROM at location 1D and verify the contents, then fitting a socket and popping it back in place if okay (or replacing with a suitably programmed EPROM if not).

If there's still no luck, send the basket-case to me and I'll kick it into shape.

VectorGlow2011-09-09 13:21:17

 

[cliff_poole]

Does the board let you start up with D05 removed ?. If it does, this will at least tell you which ROM contains which samples.

Maybe you could create a nonsense ROM image with a matching checksum and run it in MAME ?, see what that does.

 

[VectorGlow]

The samples are contained in D04 and D05 (locations 1D and 1F respectively).

From MAME:

ROM_REGION( 0x140000, "k053260", 0 ) /* samples for the 053260 */
ROM_LOAD( "072-d05.1f", 0x000000, 0x100000, CRC(1397a73b) SHA1(369422c84cca5472967af54b8351e29fcd69f621) )
ROM_LOAD( "072-d04.1d", 0x100000, 0x040000, CRC(78778013) SHA1(edbd6d83b0d1a20df39bb160b92395586fa3c32d) )

 

[cliff_poole]

OK, I misread the previous posts. I was thinking that some samples were OK and others corrupt.

 

[VectorGlow]

Not a problem.

From a message earlier in the thread (from the board owner):

"hi done a music test and they r ok..but when i done a sound test had a least 53 sound file that were bad

do u guys know what i need to fix them have wrote them all down but as i say there is about 53 bad sound samples."

 

[trm]

sadly the 3012 isn't the cause of the problem. despite being a nightmare to put in (grotty pull with creased legs in a turned pin socket). i didnt think a 3012 would be the problem with half the samples working. in my (limited) experience a fault with the 3012 would mean all samples would be garbled.

I thought all samples were duff/missing? Could you give us a summary of what is/isn't working on the audio? I concur that if there are some samples then the 3012 must be good, even if it looks like an exercising cockroach

.

 

[grobda]

samples are present. some play ok, some are distorted. chip tunes/fx all ok.

boot test all roms check ok. I went back into the test mode and in the extended rom check its flagging 1f (the eprom) as bad. the eprom verifies ok in a reader with the mame set though. so either its the wrong speed, the socket is bad or theres an associated chip malfunctioning.

the eprom is a ST M27C800-100

whole thing reeks of attempted repair bodge by the previous owner imo. i've had a look as a favour to john but if it were me i'd would've returned it before it got this far.

grobda2011-09-09 18:09:37

 

[VectorGlow]

Konami's self tests are pretty notorious for being rubbish (in my experience), so I wouldn't rely too heavily on any results. I've known them also get adjacent mask ROMs mixed up, and report one as faulty and the other okay, when the reality is the other way around.

From looking at the schems, the two mask ROMs directly connect only to the surface mounted custom (053260). Using a needle, check that no pins have come loose. Also check for corrosion.

Failing all that, I'd certainly be very tempted to remove the soldered in mask ROM and test it.

It could well be the case that the custom is duff. I think I have spares on some of my Konami parts boards.

VectorGlow2011-09-09 18:51:51

 

[cliff_poole]

I'd suspect the soldering on the replaced EPROM. Check with a meter that the tracks aren't broken, adjacent pins aren't shorted together, pins aren't shorted to ground or +5V (PCB might be new enough to have internal ground plane).

I recently received an Asterix PCB (bought as faulty), that was reporting a ROM error on start. The first thing I did was hold down the test switch then power up (this resets the EEPROM data), not expecting this to do anything. It fixed it. I didn't bother to research why, just put it down to being the easiest fix ever.