MV-1FZ Z80 Error - Where do I start?

[MrSandman]

Hi!

After endless hours of fun, my other MV-1FZ eventually broke down during game play: first the sound stopped playing, then I got a Z80 error message.
Now I get a plain Z80 error message when turning on the mobo.

Apparently *any* of the following components could be the cause for this:
Z80 CPU, 6116 SRAM IC, SM1 ROM, YM2610, or a Neo Chipset IC.

1.) I hope I have correctly identified the first 4 components (please see attachment below)?

2.) I don't know which Neo Chipset IC it is being reffered to (there are several); also rather than replacing all components, I wanted to just replace the bad one - but how do I figure that out?
I have a multimeter (VOLTCRAFT VC130 Digital-Multimeter) but where am I supposed to measure and what reading should I get?

3.) If I have correctly identified the first 4 components, then 2 of them are SMD (the Z80 and then SM1 ROM).
My soldering Iron is a very plain one, good enough for soldering wires to the JAMMA edge connector, but do I need a special tip for SMD soldering or special solder?

I am thankful for any suggestions.

Best regards,

Norman

[Rossyra]

It's pretty unlikely you will find be able to find a bad IC using only a multimeter.
But before you go there, start with the basics, do you get the test grid with no cart in? Is the cart and slot clean and making good contact?
Do you have a UniBIOS? This will allow you to skip faults in the sound system and at least get a game to boot, might help narrow down the cause.
Look for any broken traces or corrosion.
The FZ has a coin cell unlike earlier NiMH barrel-shape batteries, but may be worth checking for any PCB damage around there too.
channelmaniac is the Neo-Geo repair expert, but he's not around all that often.

[Hewitson]

If you look carefully at the NEC chip under the YM2610 you can see SM1 ROM written on it. Everything else looks correct.

Of course all components might be fine, maybe you have a damaged track on the board. I would suggest investing in a cheap logic probe.

[PrincessPrinPrin]

It could be something as simple as a bad contact between the main board and the slot board. Make sure the slot board is well pressed into the main board. If that doesn't help, start by checking the continuity of the Z80 connections (this is best done with the plastic cover off):

MV1FZ CPU2 Z80


01 A11 GU6 (13), SM1 (25), CN1 (28B), CTRG1 (54A)
02 A12 GU6 (14), SM1 (4), CN1 (29B), CTRG1 (55A)
03 A13 GU6 (15), SM1 (28), CN1 (30B), CTRG1 (56A)
04 A14 GU6 (16), SM1 (29), CN1 (31B), CTRG1 (57A)
05 A15 GU6 (17), SM1 (3), CN1 (32B), CTRG1 (58A)
06 CLK GU2 (101) 4MHz, U2 (5)
07 D4 GU1 (80), IC3 (6), SM1 (18), RAM11 (14), CN1 (13B), CTRG1 (55B)
08 D3 GU1 (77), IC3 (5), SM1 (17), RAM11 (13), CN1 (12B), CTRG1 (54B)
09 D5 GU1 (81), IC3 (7), SM1 (19), RAM11 (15), CN1 (14B), CTRG1 (56B)
10 D6 GU1 (82), IC3 (8), SM1 (20), RAM11 (16), CN1 (15B), CTRG1 (57B)
11 VCC VCC
12 D2 GU1 (76), IC3 (4), SM1 (15), RAM11 (11), CN1 (11B), CTRG1 (53B)
13 D7 GU1 (83), IC3 (9), SM1 (21), RAM11 (17), CN1 (16B), CTRG1 (58B)
14 D0 GU1 (74), IC3 (2), SM1 (13), RAM11 (9), CN1 (9B), CTRG1 (51B)
15 D1 GU1 (75), IC3 (3), SM1 (14), RAM11 (10), CN1 (10B), CTRG1 (52B)
16 INT IC3 (56), R42
17 NMI GU6 (29)
18 HALT
19 MREQ GU6 (38)
20 IORQ GU6 (39)
21 RD GU6 (35)
22 WR GU6 (36)
23 BUSACK
24 WAIT CPU2 (25), R41
25 BUSREQ CPU2 (24), R41
26 RESET IC3 (33), GU2 (169), GU6 (34), GU3 (129), CN1 (44A), CN2 (42A), CTRG1 (18B), CTRG2 (35B)
27 M1
28 RFSH
29 GND GND
30 A0 IC3 (60), SM1 (12), RAM11 (8), CN1 (17B), CTRG1 (43A)
31 A1 IC3 (61), SM1 (11), RAM11 (7), CN1 (18B), CTRG1 (44A)
32 A2 GU6 (30), SM1 (10), RAM11 (6), CN1 (19B), CTRG1 (45A)
33 A3 GU6 (31), SM1 (9), RAM11 (5), CN1 (20B), CTRG1 (46A)
34 A4 GU6 (32), SM1 (8), RAM11 (4), CN1 (21B), CTRG1 (47A)
35 A5 SM1 (7), RAM11 (3), CN1 (22B), CTRG1 (48A)
36 A6 SM1 (6), RAM11 (2), CN1 (23B), CTRG1 (49A)
37 A7 SM1 (5), RAM11 (1), CN1 (24B), CTRG1 (50A)
38 A8 SM1 (27), RAM11 (23), CN1 (25B), CTRG1 (51A)
39 A9 SM1 (26), RAM11 (22), CN1 (26B), CTRG1 (52A)
40 A10 SM1 (23), RAM11 (19), CN1 (27B), CTRG1 (53A)

[thegreathopper]

Bin it and get another it's not worth your time.

[Rossyra]

That was my first thought, if the one of SMDs does turn out to be dead, it's bin fodder.

[MrSandman]

Checked traces (corrosion etc.) but they all seem to be ok.
Cart was plugged in firmly (played it until mobo died).
Cleaned PCB with q-tips (just sudt came off).

I feared that I'd have to get another one - hoped this could turn out to be an easy fix though (oh well.... ).

Thanks anyways for your efforts and suggestions.

Edit: no cross hatch screen without cart (straight Z80 error), no UnioBOIS, cart well connected (was playing when mobo died), no damage around the battery area either; checked channel maniac's repair log before posting, great read but beyond my skills.

[Hewitson]

That was my first thought, if the one of SMDs does turn out to be dead, it's bin fodder.

Rubbish... They're very easy to desolder with chip quik or even by creating a big solder bridge around the whole IC.

[Rossyra]

Always flying in with the corrections or some other useless crap Hewitson...

I'm not making comment on the ins and outs and techniques or any other **** of replacing SMDs. It's a ten-a-penny MVS mobo. If the SMDs are dead it's bin fodder [to the the average owner, which I'll hazard a guess fits the description of the OP.]

Where will he get a replacement IC? Another mobo? Brilliant.

[MrSandman]

...to the the average owner, which I'll hazard a guess fits the description of the OP...

Yup, fits.
Will will keep my "rubbish fodder" for first-time repair practicing at some later time and return to the suggestions for more advanced MVS owners .

Anyways, thanks for your help guys.

Norman

[MrSandman]

Where will he get a replacement IC? Another mobo? Brilliant.

Hi,

Actually, I do have another (dead: VRAM error) mobo and taking one of the above mentioned ICs from that mobo and replace the bad one on the other mobo was my first idea - that's why I wanted to figure out which of the ICs was bad.

You don't seem to be convinced that that's a good idea. Is it only because a MVS mobo is cheap or are there other difficulties involved?

Thanks

[davewellington]

There's a level of expertise as well as setup required to be able to correctly diagnose and replace an IC/SMD. Preferably you have a multimeter, oscilloscope, eprom programmer, desoldering and soldering equipment, and a supergun style setup, along with a lot of patience and a willingness to learn. If you've got that, then hook up your MVS and start checking the CLK, RESET & HALT signals on the Z80 CPU.

If you don't, and you don't want to invest (an oscilloscope for example will cost 200 quid or so), then it's just easier to get another motherboard and move on.

[Rossyra]

Where will he get a replacement IC? Another mobo? Brilliant.

Hi,

Actually, I do have another (dead: VRAM error) mobo and taking one of the above mentioned ICs from that mobo and replace the bad one on the other mobo was my first idea - that's why I wanted to figure out which of the ICs was bad.

You don't seem to be convinced that that's a good idea. Is it only because a MVS mobo is cheap or are there other difficulties involved?

Thanks

Well having a spare is part of the battle you don't need to worry about. If you were in a position of searching for one, you may as well have been looking for a working one. For all anyone knows any parts mobo could be worse. Replacing SMDs is fiddly with a basic iron but definitely doable if you are a competent solderer. There are good guides to doing it on YouTube that make it look easy, but it still requires practice to get perfect. those chip quik kits cost as much as a mobo btw (in the UK), not exactly cost effective for one repair, but maybe you'll get more use out of it, or can find a cheap source somewhere.

At this point you have 2 dead mobos so I guess have nothing to lose. you still have the issue of finding the fault though. Coming at it from a standing start, the costs sure mount fast hence my 'bad idea' vibe. Good luck with your repair.

[MrSandman]

Again, thanks for the help .

Will in the near future invest in the right equipment and keep the dead mobos until then.

[Hewitson]

Always flying in with the corrections or some other useless crap Hewitson...

At this stage the most likely culprit is the z80 itself. Suggesting to bin a board because of a 2 quid part is nothing short of ridiculous, if everyone had your attitude 99% of MVS boards would be in the bin.

[purplec]

Think you get a good z80 from a game gear, which are cheap as chips.

[Rossyra]

Always flying in with the corrections or some other useless crap Hewitson...

At this stage the most likely culprit is the z80 itself. Suggesting to bin a board because of a 2 quid part is nothing short of ridiculous, if everyone had your attitude 99% of MVS boards would be in the bin.

99% of MVS boards would be in the bin? Now that's talking rubbish I stand 100% behind what I said, no guarantee it's the z80, he needs equipment to test and find the faulty the part, and probably an SMD kit to facilitate replacement - all of which will cost money too. More cost and time effective to replace the board, maybe even sell the faulty board to someone with the tools already at their disposal.