Way odd Z80 error, 2-slot sound question, and Raz, read please

A

Arakon

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I got a 2-slot today that has a z80 error. I replaced the Z80 with a Z80B. same error. I figured what the heck, and installed an unibios, same error.. then I installed the asian bios used in mv-1B/C units, which have the z80 integrated into another chip.. and it works. not only that, but I get perfect sound over the headphone jacks. sound over TV is somewhat garbled, but I'll guess that's cause the supergun is wired up for jamma standard (can someone confirm that? I used normal ground as audio ground).

any ideas why the hell it works with a bios that doesn't check for the z80, and just fine no less?

@Raz: I'd like to try that out with the newer unibios with different/disabled error checking.. when is that coming out, or could you let me test your current beta?

about sound: is it correct that any 2-slot outputs full mono sound over pin 11? if not, is it safe to wire 10+L together to create mono?

<small>[ July 26, 2003, 04:11 PM: Message edited by: Arakon ]</small>
 
A

Arakon

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ok, fixed the bad sound.. the guy apparently tried to make it mono, and abused several traces in evil, evil ways for that. which prolly killed the z80 too. the z80 error prob remains.. any ideas?

<small>[ July 26, 2003, 04:12 PM: Message edited by: Arakon ]</small>
 
S

supergoose

Die Gans,
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no, but i'm interested in the dump of MY OWN asian bios chip. :D

supergoose@gmx.de

thx.
 
A

Arakon

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to answer some of my own questions.. pin 11 is unamplified mono, volume slider has no effect. connecting pin 10+L to create mono for a standard jamma wiring works.
directly wiring 15 to M will make the test button function normally. this is all soldered on the board itself, btw.
 
Razoola

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The reason the asian bios worked is because the 1c and 1b dont have a z80 bios onboard so at startup they dont bother to check the sound hardware.

Raz
 
A

Arakon

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yes, but why does sound work flawless when the z80-checking bioses claim there's a z80 error?
 
Razoola

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maybe the onboard z80 bios has been fuxored also.

Raz
 
A

Arakon

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hrm.. I just totally redid the entire z80 area, I am absolutely sure all traces and pins are bridged right, and it still gives a z80 error.. also, I noticed that since yesterday (worked before that) the sound seems to go out after a few mins of running time, often when the screen is bright (white flashes etc). doesn't anyone have any ideas on this?
what other parts can return a z80 error (dirty cart/slot excluded), what to measure for, what pins specifically signal "z80 ok"? is this the right type of replacement chip: Z0840004P? it's supposed to be a normal Z80A (not B as I accidently wrote above).
 
ttooddddyy

ttooddddyy

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Arakon:
hrm.. I just totally redid the entire z80 area, I am absolutely sure all traces and pins are bridged right, and it still gives a z80 error.. also, I noticed that since yesterday (worked before that) the sound seems to go out after a few mins of running time, often when the screen is bright (white flashes etc). doesn't anyone have any ideas on this?
what other parts can return a z80 error (dirty cart/slot excluded), what to measure for, what pins specifically signal "z80 ok"? is this the right type of replacement chip: Z0840004P? it's supposed to be a normal Z80A (not B as I accidently wrote above).
Click to expand...
Are the two slot mobos double or triple layered (track sandwiched in the center)? I had Z80 error problems with a MVH-1 which had poor connection on the pins. Didnt realise it at the time but they have three layers of track, a rework around the Z80 fixed it :)
You could try the associated memory also.

<small>[ July 29, 2003, 02:08 AM: Message edited by: ttooddddyy ]</small>
 
A

Arakon

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seems to be the case.. bending the board a bit will sometimes make the z80 truly fail (no sound), while it works 95% of the time flawless with the 1B/1C bios, and almost always gives a z80 bios with normal bioses.. despite very randomly booting with them.

the real problem is, the neo-C1 chip is off by a good bit, while the other sound related stuff is close together.. it would take days or weeks to follow all traces. does anyone have a connection chart, i.e. pin x of the Z80 connects to pin y of the soundrom and pin z of the C1 chip? that way I could find the bad connection fairly fast.
 
ttooddddyy

ttooddddyy

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The continuity for the address and data buses on the Z80 checks out like this.

<a href="http://www.boomspeed.com/ttooddddyy/Z80pinout.doc" target="_blank">http://www.boomspeed.com/ttooddddyy/Z80pinout.doc</a>

A note on the different Z80 types.
Z80 has a max clock speed of 2.5 Meg
Z80A 4 meg
Z80B 8 meg

A Z80B will work in place of a Z80. But a Z80 may have difficulty keeping up to speed in a Z80B application. The MVS boards usually run a Z80A.

<small>[ July 30, 2003, 08:55 AM: Message edited by: ttooddddyy ]</small>
 
A

Arakon

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thanks a lot, toddy.. while your chart didn't directly fix my problem, it made me stumble over the last bad connection.. the board works flawless again.
while measuring your listed points (which all checked out ok, so I can confirm your chart), I noticed one point that didn't seem to have a good contact.. measured it, and it turns out there was no contact at all (it did have contact before I soldered the socket down, which is why I didn't re-check it later). the Reset pin of the z80 wasn't hooked up to the nearby neo-D0 chip, which resulted in this behavior (apparently the old bioses tried to reset the z80, and it wouldn't, so they error out.. while the asian bios doesn't look for a z80, so it worked).

damn, I think this is the most trouble I ever had with fixing a board.. thanks to everyone who helped out.

<small>[ July 30, 2003, 10:56 AM: Message edited by: Arakon ]</small>
 
ttooddddyy

ttooddddyy

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Do the MV2 slot boards have three layers of track ?

All I know is that 6 slots are only double sided, MVH-1 is triple track (think the other single boards are just double sided)

<small>[ July 31, 2003, 08:17 AM: Message edited by: ttooddddyy ]</small>
 
A

Arakon

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I'm not entirely sure, but going by the looks of it I'd say just two-sided.
 
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