MV1B needs to change bios in order to get sound?

bytestorm

bytestorm

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Hey!

I have a nice looking mv1b that outputs no sound, only a buzz when making the volume high.. and it also reports M1 rom error in the beggining of the boot.. tried a couple of legit games that works in my mv1c, they all report m1 rom error..

then I found some info somewhere (lost the link) about that the MV1B needs the bios changed to work?? I have a spare neobiosmasta for mv1b/c.. I understand that there are 2 versions of the mv1b board, one for irritating maze only, and one regular. how can i see wich i got?

the bios have SP-3 on it, and the silkscreen under the pcb says:

NEO-MVH MV1B
1996.1.19

any thoughts?
 
Xian Xi

Xian Xi

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Make sure both parts of the MV1B are pushed together tightly. Split them then put them back together.
 
bytestorm

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Xian Xi said:
Make sure both parts of the MV1B are pushed together tightly. Split them then put them back together.
Click to expand...

Already tried that :(. Cleaned the slot also, and the pcb is i very good condition. When I can make the buzzing higher and lower that should mean the audio circuitry is worki g at least .. but I cant understand why the m1 error gets reported. Maybe I need to make myself one of snkdan test carts.. that might be worth a try. Or maybe the neo bios astaire alone could shed some light on the error as well.
 
Xian Xi

Xian Xi

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From what I remember it could be a bad trace from the cart slot to the YM2610/Z80. Just to confirm, it's an M1 error and not an SM1 error, correct?
 
bytestorm

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Yes it's M1 :/.. I'll check the trace tomorrow when I install the uni bios adapter. Just made the smkdan test cart also :)
 
bytestorm

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this info from smkdans page is awesome! the chase is on!

YM2610 I/O ERROR

YM2610 isn't responding to the Z80 reads and writes as expected. Most likely a bad trace between the Z80 and YM2610 but it could also mean a faulty 2610. This is the first 2610 test to check that it's actually functioning and accessible. Games will likely run but they'll be completely muted.

Z80 D0~D7 → YM2610 D0~D7
Z80 A0/A1 → YM2610 A0/A1
Z80 A2~A4 → NEO-D0 SDA2~SDA4
Z80 IORQ (20) → NEO-D0 IORQ (37)
Z80 RD (21), WR (22) → NEO-D0 SDRD (35), SDWR (36)
NEO-D0 2610RD (48), 2610WR (47), 2610CS (49) → YM2610 RD (59), WR (58), CS (57)
 
Xian Xi

Xian Xi

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It might be something as simple as a dirty pin/contact on the board connectors. Pull the boards apart and check the connectors. I once had one that had corrosion inside one of the connectors. Check continuity between the Z80 and YM2610. You'll find which ones are disconnected easily.
 
bytestorm

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Xian Xi said:
It might be something as simple as a dirty pin/contact on the board connectors. Pull the boards apart and check the connectors. I once had one that had corrosion inside one of the connectors. Check continuity between the Z80 and YM2610. You'll find which ones are disconnected easily.
Click to expand...

Yeah I'll take it apart tomorrow again. But how come I can hear the test tones?? But games are muted...??
The test bios/cart makes some tones and stuff while testing.. it's all clear and hear able. Strange :/

I changed all the caps today in case.. and also the volume pot. But no difference :(
 
bytestorm

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Checked it all today.. no faults found :(.. even wiggling the connector while I measure but it's all good.. still I wonder how I can hear the test tones when I can't hear any music or other sound effect in game?
Althou it hit me now that I could maybe try and reflow the solder joints on the involved circuits ... hmm I'll do that tomorrow!

Really hope I don't have a dead 2610.. :(
 
Atro

Atro

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I had an MV1B with the exact same problem as yours.
On my case, it was the YM2610 that was dead. Luckily I had other MV1B's around to swap the top part to test it.
It ruled out. It worked right away.

You have a PM coming.
 
Xian Xi

Xian Xi

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The tones iirc come from the SM1. Check the IRQ line on the 2610, I think it's pin 54 or 56(check the datasheet) if it's reading high logic then it's still good but if it's reading low then you need to swap it out.
 
Atro

Atro

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Xian Xi said:
The tones iirc come from the SM1. Check the IRQ line on the 2610, I think it's pin 54 or 56(check the datasheet) if it's reading high logic then it's still good but if it's reading low then you need to swap it out.
Click to expand...

You never cease to amaze with that knowledge.
I'm sending a spare top part to Bytestorm to see if it clears the problem.
 
bytestorm

bytestorm

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Hi!
Finally got time to try it again with the new top but it's still no sound.. :(..
Will see if I can get some time with the scope in the weekend to check the Z80.

; (
 
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