Backup RAM on NEO-GEO MV1FZ

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arakissun

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Can anyone tell me where is located backup RAM on NEO-GEO MV1FZ?(with picture if it possible)
When I power on it say:

"Backup RAM ERROR"

I know for the other fixes about bad traces and battery,but when I start to repair the board I want to know and the location of SRAM
I search google but with no luck


Thank you
 
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arakissun

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Ok
How can I understand which of these two sram is not working?
It's not problem to replace both


Thank you
 
Last edited:
Xian Xi

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You can use a multimeter and check continuity from the ram.
 
channelmaniac

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Look for rodent damage (piss on the board and corroded traces) and check the R/W, OE*, and CE* lines on the SRAMs with a logic probe.

If those signals are missing you'll get BACKUP RAM errors....

Of course, it could be a bad RAM chip too. Post the full error message and we'll be able to tell more of what is going on.
 
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arakissun

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This is the error:



Backup Ram Error

ADDRES WRITE READ
00D00000 5555 B255


I replace the SDRAMs and will test it tonight


I want to know what means B2 and 55 in READ
Also who are the R/W, OE*, and CE* lines on the SRAMs
 
channelmaniac

channelmaniac

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The system writes a set of data to the SRAM chips and reads it back. If the data read doesn't match the data written then you get an error.

Look at it in binary instead of hexadecimal and you'll see what data lines are wrong.

55 = 01010101
B2 = 10110010

R/W* = read/write. The * signifies that it's active low. So when the line is high you can read the chip. When low you can write to it.

CE* = Chip Enable. The chip is enabled for reading or writing when this line is held low.

OE* = Output Enable. The data is output from the chip when this line is held low.

These SRAM chips are surface mount. If you don't know what you are doing then you'll severely damage the board when trying to replace them.

RJ
 
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arakissun

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Ок.I replace the chips but with no effect-same error
Yes,they are mount,and I can do this by myself.I have experience in this
Any suggestions?


Thank you
 
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Xian Xi

Xian Xi

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arakissun said:
Ок.I replace the chips but with no effect-same error
Yes,they are mount,and I can do this by myself.I have experience in this
Any suggestions?


Thank you
Click to expand...

Everyone says they have experience doing these things but these SRAM chips are very sensitive and you need to be very careful installing them as they can easily die when mishandled. They are very sensitive to static electricity as well.

If you replaced them properly and you still get an error then it's most likely a bad trace or corroded plate-through.
 
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arakissun

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What I need to check then?

One more
If I replace the original BIOS with UniBIOS?
I read that I cant bypass the test?

What chip EEPROM or EPROM I need to burn the BIOS?
The read_me file say:

"To burn the ROM,you NEED 27C1024 EPROM"


Ok,but the original BIOS is EEPROM chip

Thank you
 
Last edited:
channelmaniac

channelmaniac

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Get a logic probe and check the control signals like I said.

If the chip isn't bad then you have a bad trace somewhere.

The original BIOS isn't an EEPROM. It's a Mask ROM.
 
Xian Xi

Xian Xi

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arakissun said:
What I need to check then?

One more
If I replace the original BIOS with UniBIOS?
I read that I cant bypass the test?

What chip EEPROM or EPROM I need to burn the BIOS?
The read_me file say:

"To burn the ROM,you NEED 27C1024 EPROM"


Ok,but the original BIOS is EEPROM chip

Thank you
Click to expand...

Fix the RAM problem first before swapping in a new bios. Like RJ said use a logic probe to check the signal lines. Check if they are reading high or low and check it against the data he posted as to what state the RAM is in. If you get no signal then that trace/platethrough is bad possibly.


Can you post a pic of the chips you soldered in?
 
MKL

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Check the connections:

Code: 
MV1FZ  Backup RAM

RAM3

1	RAM4 (1), RAM1 (1), RAM2 (1), CPU1 (46), GU5 (33), SP1 (36), CN2 (24A)
2	RAM4 (2), RAM1 (2), RAM2 (2), CPU1 (44), GU5 (31), SP1 (34), CN2 (22A)
3	RAM4 (3), RAM1 (3), RAM2 (3), CPU1 (39), GU5 (17), SP1 (28), CN2 (17A)
4	RAM4 (4), RAM1 (4), RAM2 (4), CPU1 (38), GU5 (16), SP1 (27), CN2 (16A)
5	RAM4 (5), RAM1 (5), RAM2 (5), CPU1 (37), GU5 (15), SP1 (26), CN2 (15A)
6	RAM4 (6), RAM1 (6), RAM2 (6), CPU1 (36), GU5 (4), SP1 (25), CN2 (14A)
7	RAM4 (7), RAM1 (7), RAM2 (7), CPU1 (35), GU5 (3), SP1 (24), CN2 (13A)
8	RAM4 (8), RAM1 (8), RAM2 (8), CPU1 (34), GU5 (2), SP1 (23), CN2 (12A)
9	RAM4 (9), RAM1 (9), RAM2 (9), CPU1 (33), GU5 (1), SP1 (22), CN2 (11A)
10	RAM4 (10), RAM1 (10), RAM2 (10), CPU1 (32), GU5 (64), SP1 (21), CN2 (10A)
11	RAM2 (11), SP1 (19), CPU1 (5), U8 (18), GU7 (6)
12	RAM2 (12), SP1 (18), CPU1 (4), U8 (17), GU7 (7)
13	RAM2 (13), SP1 (17), CPU1 (3), U8 (16), GU7 (8)
14	GND
15	RAM2 (15), SP1 (16), CPU1 (2), U8 (15), GU7 (9)
16	RAM2 (16), SP1 (15), CPU1 (1), U8 (14), GU7 (11)
17	RAM2 (17), SP1 (14), CPU1 (68), U8 (13), GU7 (12)
18	RAM2 (18), SP1 (13), CPU1 (67), U8 (12), GU7 (13)
19	RAM2 (19), SP1 (12), CPU1 (66), U8 (11), GU7 (14)
20	U17 (2), Q1 (collector)
21	RAM4 (21), RAM1 (21), RAM2 (21), CPU1 (42), GU5 (20), SP1 (32), CN2 (20A)
22	GU1 (97)
23	RAM4 (23), RAM1 (23), RAM2 (23), CPU1 (43), GU5 (21), SP1 (33), CN2 (21A)
24	RAM4 (24), RAM1 (24), RAM2 (24), CPU1 (41), GU5 (19), SP1 (31), CN2 (19A)
25	RAM4 (25), RAM1 (25), RAM2 (25), CPU1 (40), GU5 (18), SP1 (29), CN2 (18A)
26	RAM4 (26), RAM1 (26), RAM2 (26), CPU1 (45), GU5 (32), SP1 (35), CN2 (23A)
27	U17 (8)
28	VCC


RAM4

1	RAM3 (1), RAM1 (1), RAM2 (1), CPU1 (46), GU5 (33), SP1 (36), CN2 (24A)
2	RAM3 (2), RAM1 (2), RAM2 (2), CPU1 (44), GU5 (31), SP1 (34), CN2 (22A)
3	RAM3 (3), RAM1 (3), RAM2 (3), CPU1 (39), GU5 (17), SP1 (28), CN2 (17A)
4	RAM3 (4), RAM1 (4), RAM2 (4), CPU1 (38), GU5 (16), SP1 (27), CN2 (16A)
5	RAM3 (5), RAM1 (5), RAM2 (5), CPU1 (37), GU5 (15), SP1 (26), CN2 (15A)
6	RAM3 (6), RAM1 (6), RAM2 (6), CPU1 (36), GU5 (4), SP1 (25), CN2 (14A)
7	RAM3 (7), RAM1 (7), RAM2 (7), CPU1 (35), GU5 (3), SP1 (24), CN2 (13A)
8	RAM3 (8), RAM1 (8), RAM2 (8), CPU1 (34), GU5 (2), SP1 (23), CN2 (12A)
9	RAM3 (9), RAM1 (9), RAM2 (9), CPU1 (33), GU5 (1), SP1 (22), CN2 (11A)
10	RAM3 (10), RAM1 (10), RAM2 (10), CPU1 (32), GU5 (64), SP1 (21), CN2 (10A)
11	RAM1 (11), CPU1 (65), SP1 (10), GU2 (13), CN2 (14B)
12	RAM1 (12), CPU1 (64), SP1 (9), GU2 (14), CN2 (15B)
13	RAM1 (13), CPU1 (63), SP1 (8), GU2 (15), CN2 (16B)
14	GND
15	RAM1 (15), CPU1 (62), SP1 (7), GU2 (16), CN2 (17B)
16	RAM1 (16), CPU1 (61), SP1 (6), GU2 (18), CN2 (18B)
17	RAM1 (17), CPU1 (60), SP1 (5), GU2 (19), CN2 (19B)
18	RAM1 (18), CPU1 (59), SP1 (4), GU2 (20), CN2 (20B)
19	RAM1 (19), CPU1 (58), SP1 (3), GU2 (21), CN2 (21B)
20	U17 (2), Q1 (collector)
21	RAM1 (21), RAM3 (21), RAM4 (21), CPU1 (42), GU5 (20), SP1 (32), CN2 (20A)
22	GU1 (13)
23	RAM3 (23), RAM1 (23), RAM2 (23), CPU1 (43), GU5 (21), SP1 (33), CN2 (21A)
24	RAM3 (24), RAM1 (24), RAM2 (24), CPU1 (41), GU5 (19), SP1 (31), CN2 (19A)
25	RAM3 (25), RAM1 (25), RAM2 (25), CPU1 (40), GU5 (18), SP1 (29), CN2 (18A)
26	RAM3 (26), RAM1 (26), RAM2 (26), CPU1 (45), GU5 (32), SP1 (35), CN2 (23A)
27	U17 (6)
28	VCC

The problem is related to RAM3. RAM4 is OK.
 
Hewitson

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So follow the circuit backwards from the RAM to the logic that controls it.
 
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arakissun

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What is the point,the connections are ok.Sorry for the questions but this is my first time experience with neo-geo mobo

One thing:
So when the connections i OK,then CS,OE,W/R are ok too?
 
Last edited:
channelmaniac

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Not necessarily.

You may have a broken trace on the other side of a chip causing a missing signal... or you may have a bad chip that isn't sending the proper signal to the SRAM.

This is why you need a logic probe. You may have replaced chips that didn't need replacing.

RJ
 
MKL

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If all the connections I've posted are OK (double/triple checked them??), then it could be the WE (pin 27) of RAM3. CE (pin 20) is in common to both RAM ICs and RAM4 is OK so it can't be that. OE (pin 22) is directly connected to GU1 (97) and you said it's OK. Then we are left with WE which is the output of an OR gate in U17 (74HC32). Check the inputs of that gate, in particular pin 10 that must be connected to GU1 (98).
 
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arakissun

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I bought Logic Probe but I'm not sure how to use it.
I see MEM and PULSE,also CMOS and TTL
How must be configure to check the signals ?
 
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arakissun

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I still cannot repair the error,so I think about to replace the BIOS with UNIBIOS.
Now when I replace it,is menu "HW TEST" will be turn on or turn off by default.If its turn "OFF" by default this mean that it will bypass the ram test and will star the board without remember the high score,BIOS setup-this is not a problem for me
I think this is the function of the backup RAM.Is that right?

And the other-If "HW TEST" is "ON" by default,this mean that the problem with starting will remain ,because the backup ram error will show up
In this case(if its "ON") can I edit ROM file of the UniBIOS and make change to start with "HW TEST OFF"
 
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