@Retro Mecano what are the hc32's function in the sound circuit?
What sound code do you get when running the test cart?
What sound code do you get when running the test cart?
MV1AX. Z80->68k comm issue (ack)
- Thread starter kissedin
- Start date
Retro Mecano
Enthusiast
Not sure of the function, specially with these damn bufs.. but the diag test gives me 001100 code.
On previous slots (regular like FZ and 2F etc..) i had the same error, 1 time a faulty NeoC1 and another a faulty 6216 ram.
Since we almost changed everything in the board, and i didnt see before an sm1 fail on my watch, i will gamble on reswapping the NeoD0.
I was also thinking of the PAL 1B as it has some kind of ack signal with 68k, but i dont have spares either.
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Dtack is for the 68k. I dont think you would be able to run anything without it.
Maybe you could try swappibg SNK1A? It generates SDW. Pin 22 (output) to u10 pin 11 (clock) and neo-D0 pin 33 (SDW).
(From Neo dev wiki: SDW signals that the 68k has written a byte to the Z80 port, will make NEO-D0 generate an interrupt if enabled.)
(I have checked mine SDW but it is behaving exactly like it does on a working board I have.)
Maybe you could try swappibg SNK1A? It generates SDW. Pin 22 (output) to u10 pin 11 (clock) and neo-D0 pin 33 (SDW).
(From Neo dev wiki: SDW signals that the 68k has written a byte to the Z80 port, will make NEO-D0 generate an interrupt if enabled.)
(I have checked mine SDW but it is behaving exactly like it does on a working board I have.)
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maki
Student
Have you check all traces for the P-Bus?
Bad connections can lead to this kind of error (floating datalines).
here is a simple test for the Z80/68k comms using a logic probe:
View: https://www.youtube.com/watch?v=__qTYNFvl3I
However that seems to work for you.
The NEO-BUF are used to mulitplex data, they are susceptible as well, the MV1AX has plenty of them.
They have a tendency to fail in part, however since is working and then not working, guess is bad traces for now.
furrtek sells replacement https://www.furrtek.org/shop/
Bad connections can lead to this kind of error (floating datalines).
here is a simple test for the Z80/68k comms using a logic probe:
However that seems to work for you.
The NEO-BUF are used to mulitplex data, they are susceptible as well, the MV1AX has plenty of them.
They have a tendency to fail in part, however since is working and then not working, guess is bad traces for now.
furrtek sells replacement https://www.furrtek.org/shop/
maki
Student
Try pressing in the ICs/board while the test is running, see if you find an area to press on that changes the outcome of the test
Oh trust me, I have pressed and wiggled and bent
maki
Student
last thing I can think of the the slot PCB, it only has a single IC (U1) but tons of soldering points, traces and of corse the slot itself which is also susceptible to dirt/corrosion, but also the connectors to the PCB, same goes for them
Hmm ... That is an idea. There is a ls245 mounted on the slot pcb (if my memory serves me right). But a faulty slot pcb wouldn't explain why I don't get sound in the stock bios test menu...
I'll try it anyway. Maybe there are two faults.
Both error codes point to the same thing
001100 - z80 never got the handshake (0x5a) response from the 68k
001101 - z80 got the handshake (0x5a) response from the 68k, but when the z80 tired to clear the latch after, it didn't clear
Is it possible you have a floating data line from the latch to the z80 and its causing a random high/low state? That could also explain why it passed all tested once as well as stock bios not being able to do the sound test.
Finally some progress. I've checked all latches and their data lines with certain regard to floating signals. But no findings.
Decided to change my furrtek repro at GA9 "because it just had to do something with that chip". But by now i had run out of repros. So I used the snk one that used to be in position GA4.
Powered on. All tests passed with diagrom. Tried multiple times. Tested OK. Put in stock bios and ... SOUND! Put in 3 count bout - samples, eycathcer music - working like a charm.
Put in KOF'99 and ... Silence. Then a long tone of some kind. When eycathcer music is supposed to be playing it is silent.
Ran diagrom for like 5 minutes but "all tests pass" every single time. KOF'99 play good in my other neo-geos. Tried metal slug x (because that is a newer game like KOF'99) and this one is silent as well.
Any help is of course highly appreciated.
Decided to change my furrtek repro at GA9 "because it just had to do something with that chip". But by now i had run out of repros. So I used the snk one that used to be in position GA4.
Powered on. All tests passed with diagrom. Tried multiple times. Tested OK. Put in stock bios and ... SOUND! Put in 3 count bout - samples, eycathcer music - working like a charm.
Put in KOF'99 and ... Silence. Then a long tone of some kind. When eycathcer music is supposed to be playing it is silent.
Ran diagrom for like 5 minutes but "all tests pass" every single time. KOF'99 play good in my other neo-geos. Tried metal slug x (because that is a newer game like KOF'99) and this one is silent as well.
Any help is of course highly appreciated.
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maki
Student
you found the issue with a NEO-BUF replacement, great work
have you checked the voltage on the +5V rail?
especially with the new games
below 4.75V and its expected to act up
have you checked the voltage on the +5V rail?
especially with the new games
below 4.75V and its expected to act up
Kinda sounds like a dirty cart or slot. You might try (re?) cleaning both. Additionally try fully inserting the cart then backing it out a few mm and try it like that.
Retro Mecano
Enthusiast
Assuming you aren't getting palette ram errors. I would check on the inputs/outputs of the 2x 74LS273's at U8 and U9 to the lower left of the bios chip. It should go palette ram data -> 273s -> resistors on the under side -> jamma rgb pins.
Is it possible that a faulty Neo buf at GA4 can interfere with the data bus on GA9? They are in parallell after all.
I replaced my buf at GA4 and that made a change on my comm isssue. BUT that also might've been a pure coincidence since I got multiple different errors after that change.
(I was quite confident it was just a coincidence, that is why I put the same chip in GA9 after this ... I have ordered more repros btw)
Regarding my KOF'99 struggle: I check continuity w. multimeter from slot pcb to cart-pcbs. I doubt it. But I'll try. I guess I should focus on the progboard since the chaboard-connector has been tried out during all the diagrom-tests.
Please note that the KOF'99 board is running perfect on all my other neo-geos. Also note that I have a spare MV1AX-slot pcb that is giving the exact same error.
(Right now I'm comparing how the pcm chip on KOF'99 behave between a working board and my faulty. And what differs a game like 3 count bout (which works) and kof99 on my faulty.)
I replaced my buf at GA4 and that made a change on my comm isssue. BUT that also might've been a pure coincidence since I got multiple different errors after that change.
(I was quite confident it was just a coincidence, that is why I put the same chip in GA9 after this ... I have ordered more repros btw)
Regarding my KOF'99 struggle: I check continuity w. multimeter from slot pcb to cart-pcbs. I doubt it. But I'll try. I guess I should focus on the progboard since the chaboard-connector has been tried out during all the diagrom-tests.
Please note that the KOF'99 board is running perfect on all my other neo-geos. Also note that I have a spare MV1AX-slot pcb that is giving the exact same error.
(Right now I'm comparing how the pcm chip on KOF'99 behave between a working board and my faulty. And what differs a game like 3 count bout (which works) and kof99 on my faulty.)
Retro Mecano
Enthusiast
Dude i respect your patience. I swear it will be the last MV1A variant i repair..
I can't even handle the repair logic since errors now make absolutly no sense after each fix. I repair 1 error, 2 other pop up. I repair a second one, the first error pop up again...
Almost swapped every damn IC related to sound (except SM1) and now the error is stubborn on communication issue again, wich i fixed few days ago.
Can't trust these BUFs. May be it gets worst with the heating and reheating the PCB.
One thing I noticed is that some of these NEO-BUF repros have solder between the legs on the super tiny ls245 chips. There is quite often a short between the NC on the chip and its neighbouring pin, but this seems to have no matter. But sometimes the data lines are shorted...
(This is no critique; I am super thankful for being able to buy these repros - and for such a good price.)
(This is no critique; I am super thankful for being able to buy these repros - and for such a good price.)
Small update. Swapped slot pcb with known working board. Result: slot pcb is not the problem.
Probing pcm chip on KOF'99. There is a lot of dead data and adress lines. Could it be that the m1 rom isn't properly executed?
Suspecting Neo buf at GA9 but also zmc2. (My zmc2 is a new repro but maybe sloppy solderjob by me)
Probing pcm chip on KOF'99. There is a lot of dead data and adress lines. Could it be that the m1 rom isn't properly executed?
Suspecting Neo buf at GA9 but also zmc2. (My zmc2 is a new repro but maybe sloppy solderjob by me)