Z80 Error

Hit a dead end, I have no idea how to check these chips, think it's time to throw in the towel. Does anybody know of any repairers in the UK?

Failing that, what other MVS boards have the same dimensions as the MV1FZS? I have it setup in a crappy wooden box, so I would like something of identical size, so I can just slot it in and plug in the jamma connector.
Also, where's a good place to buy from, I bought this from ebay with 2 games thrown in for £60, yet looking around, just the board on it's own is over £100 at the moment!

Edit - I caved in, I've bought a MV1FZ, £60 delivered, maybe I could try to repair my old one, or just use it for spares.

It's most likely a bad T84C00AM-6 chip.
BB

DEL 707 said:

Hit a dead end, I have no idea how to check these chips, think it's time to throw in the towel. Does anybody know of any repairers in the UK?

Failing that, what other MVS boards have the same dimensions as the MV1FZS? I have it setup in a crappy wooden box, so I would like something of identical size, so I can just slot it in and plug in the jamma connector.
Also, where's a good place to buy from, I bought this from ebay with 2 games thrown in for £60, yet looking around, just the board on it's own is over £100 at the moment!

Edit - I caved in, I've bought a MV1FZ, £60 delivered, maybe I could try to repair my old one, or just use it for spares.

Click to expand...

at the monent the £60 you have paid is about average (sadly) on ebay
you can usually pick one up on one of the forums for around £10-15 less

Even though my new boards on the way, I can't let this go, was sat there at 1 am last night, by lamp light, checking for any obvious damage.
If it was completely dead, I could accept it, but with just a sound problem, it's starting to grate on me.

I was going to take it in to work to have a look at it with the boss' old osciloscope, but dragging my MVS and all it's bits to London on a train in rush hour wouldn't be much fun.
It looks like you can pick up logic probes for about 20 quid. Do they do the same sort of job?

Well the boss dusted off his oscilloscope, literally, and had a look at this for me. Checking out the Z80 RAM, which he believed would be the most likely suspect. He found that data line 6 looking a bit iffy, think it was pin16.

This was a *normal* datatine



This was data line 6



Which he thought was a bit weird.
Again, I have no experience in these things and it's he's 1st time looking at something like a Neo Geo. Is there anyway to narrow this down?

Failing that, how hard/expensive is it to get these parts, my boss is putting money on the Z80, which I'll just replace if it's cheap enough...

Wanted to reactivate my long-dormant account to bump this super useful thread and post a repair log. Thanks to all who contributed above!

The PCB was a MV-1FZ bought as non-working along with 3 other dead boards. It still had the factory battery (which still had 0.5V across it!) and no obvious signs of leakage, corrosion or burnt traces.

When powered it gave a backup RAM error, wrote 5555 and read 4255. One of the other boards was badly mangled from previous "repair" attempts so I replaced the high SRAM with a chip from this board - with no effect. Poking around with a logic probe I found a stuck output from the 74HC32 in the backup RAM area that runs the chip selects, and replacing this IC cured the RAM error.

On booting for the first time I was ecstatic to see the crosshatch screen for the first time! But when I plugged the cartridge slot riser PCB back into the mainboard and attached a cartridge, on all further power cycles it just gave a Z80 error. I guess the stress of being powered up for the first time in ten years was too much for it

Checked all the address and data lines from the sound maskrom to the 6216 and the Z80 and all were good. Didn't see anything unusual with the logic probe either. I reflowed the YM2610 and RAM + ROM just in case any crap bubbled to the surface but all the joints looked good. So as suggested here I desoldered the Z80 and found a huge amount of burnt-looking brown crud covering all the vias underneath it. Gave this a good scrub clean with isopropanol and then replaced the Z80 with the one off the parts board and it booted up successfully

So all praise to the gurus, and I finally have an MVS board that works immediately prior to going on holiday to Japan. This could get expensive

Thanks guys!

Stone