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HornheaDD

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I bought a non-working MV1FS from Bill Berger (I was fully aware it has no video). But that's all I know at the moment. It's coming in the mail soon, and I'd like to find out what kinds of things to look out for with non-working boards to see if I can bring it back from the dead.

I bought it as a project. I am an amateur solderer, and just want to learn. It was $40 so if I never get it working, I'm only out $40. But if I can get it working, maybe I can learn to consolize it down the line, I dunno. I dont have it yet, should be here this week I believe. But I just wanna get a jump on trying to figure out what might be wrong with it and maybe get it running.

UPDATED: Got the board today and to my surprise it booted right up without any video issues. I think Bill must have been mistaken, because the issue is no sound, which I would possibly bet that its a simple(r) fix. Any ideas on this? I can take some pics of the board if need be, but at least on a cursory inspection, it looks like its all ok.
 
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HornheaDD

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Off work, so I decided to fiddle around. Here's what I know so far:

The volume pot will make a difference in what I 'hear'. Its just your standard speaker hiss, but it WILL change the volume if the pot is turned up or down.
Tried a JPN BIOS, as well as an older UniBIOS I have layin around (still got my old purchased one from Raz :)) and they did not make a difference. I dunno if that was to be expected, but it wouldn't hurt to try, right?
Going into the hardware test menu via dip switches, I was able to test the speakers, and I successfully heard the little "ooo" tone from the left, right and stereo selections. Doesn't that right there tell us that the board has working sound?

A cursory examination of the board shows that it's pretty damn clean for being ancient, and it doesn't look like any parts are broken. I tried it with an actual Neo cart, as well as the other Banana cart I have, and still nuffin.

Any ideas as to what might be the cause of this?
 

Rom1

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If you have sound in bios it means hardware is not that bad. It might be a bad sound ROM switching or bad traces to it.

Using Unibios check if the Z80 works correctly when using M1 from the cart.
Check all traces between M1 and motherboard.
 

HornheaDD

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Ill try that. It'll have to be after work, but I'll check it and report back. Thanks for the suggestion!
 

thegreathopper

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Pleased to hear Bill Berger is still selling, I bought loads from him back in the early 2000’s.
 

HornheaDD

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If you have sound in bios it means hardware is not that bad. It might be a bad sound ROM switching or bad traces to it.

Using Unibios check if the Z80 works correctly when using M1 from the cart.
Check all traces between M1 and motherboard.
Got off work and, I have to apologize, Im a little usure how to do what you mentioned. I tried it on the UniBIOS 3.0, as well as 4.0, the only thing that seemed like a test you mentioned is the GameCart Check screen. I didn't take a picture of mine, (I can if need be tho) but it basically looked like the one on the UniBIOS home page:

1648333238364.png


ROM Region and Bank 0 came up with an OK, but banks 1, 2 and 3 were 'not used.'

Is there somewhere else I can specifically test M1?
 

hatmoose

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Using Unibios check if the Z80 works correctly when using M1 from the cart.
Check all traces between M1 and motherboard.

I think rom1 was talking about the diagnostics bios and the companion z80 test cart?

You can download both the bios and the s1 test rom here.
http://smkdan.eludevisibility.org/neo/diag/
Or an updated one here
https://github.com/jwestfall69/neogeo-diag-bios

The diagnostic bios is easy enough, burn it to a suitable EPROM, buyicnow will supply the eprom and burn it if you want

Making the z80 test cart is a bit more complicated, I wrote about my adventures here
https://www.arcade-projects.com/thr...-diagnostics-bios-z80-test-cart-m1-bin.17651/
 
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HornheaDD

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Oh, I see. Someone in a facebook group did mention the diag bios, but unfortunately I don't have an EEPROM burner, so I'll look into buyicnow. Thanks for the heads up! I bought a logic probe to test like Brian Hargrove did in one of his vids. It was $20 so I figured why not.

Edit: Oh wait, it appears the test cart is required for those BIOS. :(
 

Rom1

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Diagbios test cart is indeed useful but i was talking about unibios jukebox.

When using the jukebox it switches to M1 rom on the cart. If sound system is unresponsive, it means a problem with cart comm'.
 

HornheaDD

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Diagbios test cart is indeed useful but i was talking about unibios jukebox.

When using the jukebox it switches to M1 rom on the cart. If sound system is unresponsive, it means a problem with cart comm'.
Oh I see, ok. Yeah I tried the jukebox, but heard no music.

Does that mean there's an issue with the cart connector?
 

Rom1

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Very probable there is an issue with connectivity.

Can be connector, broken trace, ...
 

HornheaDD

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Ok! Looks like I need to find a schematic of the board, get my magnifying glasses and see what I can find.
 

HornheaDD

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Small update, I tested the digital audio like the test from ArcadeComponents and it seems that the digital audio is functioning as designed. I got a logic probe today from Amazon and tested it, and I am getting the steady beeping and static like in the video. So that's a little progress there. I finally have some time to get my vision visor on and see if I can find any messed up traces.
 

HornheaDD

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Small update again. I was using this image to figure out what pins are what on the Z80:

https://wiki.neogeodev.org/index.php?title=File:Z80_pinout.png


So pin 27 goes to the M1. That side of the chip looked a little dirty so I cleaned it up, and ran my soldering iron across the legs to do a pseudo reflow (let it be known I am not a professional solderer. I would consider myself a beginner, not even amateur) and the legs looked a little better. Tried it, and still no sound. I figured that would happen lol but its worth a shot!

Here's my issue now - I cant seem to find where the line for pin 27 even goes so I can attempt to trace it :(

I don't have a macro lens on my phone so if I took a picture it would look terrible. But the pin 27's "leg" connects to the pcb, but it doesn't "travel." I cant follow it's trace because it doesn't seem to go anywhere. It sort of disappears into the PCB. It goes "down" into the PCB, if that makes any sense at all. I tried flipping the board over and I'm fairly (90%) certain I found where on the board the pin is, and from what I can tell it doesn't show up on that side either.

I found some schematics of the cartridge slot for the MVS boards so I could see if there was any continuity between the pin and whatever pin corresponds to it on the cart slot, but I unfortunately couldn't make out what the schematic labels were. The scans on NeoGeoDev are difficult to make out. I tried zooming in using an image viewer, but it didn't make much of a difference:

https://imgur.com/EKSDPtc

For all I know I'm looking in the wrong area, but as far as locating the Z80, I'm pretty sure I located it successfully, as well as the M1 pin (27). Does anyone possibly know what pin on the cart slot corresponds to Pin 27?
 

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i dont see why the neogeo would need the z80 M1 signal, it's mostly usesd for encrypted games on other systems.
M1 signals that the cpu is reading an instruction from memory, as opposed to reading data.
if i'm remembering it right.
 

HornheaDD

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i dont see why the neogeo would need the z80 M1 signal, it's mostly usesd for encrypted games on other systems.
M1 signals that the cpu is reading an instruction from memory, as opposed to reading data.
if i'm remembering it right.

Im at a loss man, you guys are talking about stuff that's way over my head lol. What do you think it might be?
 

Rom1

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At first you should verify for activity on the OE of the M1 ROM. You should also check U13 (hc32) activity, or simply change it.
Also, you should look at activity of Z80, both with and without cart. The reset and halt should be high, M1 pin should pulse, it's like AS on 68k. The IRQ should pulse too.
 

HornheaDD

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At first you should verify for activity on the OE of the M1 ROM. You should also check U13 (hc32) activity, or simply change it.
Also, you should look at activity of Z80, both with and without cart. The reset and halt should be high, M1 pin should pulse, it's like AS on 68k. The IRQ should pulse too.
That went completely over my head :/
 
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