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MVS 2 Slot Repair Help

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r67055

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Hi!

I want to ask for help.
I have a MV2F MVS PCB. I put any game card in it, it just shows a grid image.
I cleaned both slots. I checked the corrosion lines. but I found no signs of damage. I took out the Diagnostic Rom. I see all tests as good.
Does anyone know what I can do after this?


Thanks
 

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Perhaps try source some replacement slots / check the existing slots for damage on the pins.
 
maybe you can see something?

it would be a lot of work to change the sockets :((((

which one should I start the exchange with?
 

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this pcb was put away in a box about 2 years ago together with a 4 slot mvs. both were still working. I just took it out and both were faulty. inserted cards do not start. I don't understand what could have happened.
 
I cleaned the sockets.
I thought I'd check it out. but all pins are in contact.
I used the multimeter on both sides of the pcb.
 

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What I normally do in this situation is to use unibios with a known working cart inserted. At unibios's crosshatch screen there is an option to do the memory viewer, pick that then scroll down to address 000100. At that location on a working cart/board you should see "NEO-GEO" on the right as seem below

IMG_0474.jpg


If there is a data/address issue between the board/cart the NEO-GEO will be corrupt. What the corruption is can point to whats causing the problem.
 
ack said:
What I normally do in this situation is to use unibios with a known working cart inserted. At unibios's crosshatch screen there is an option to do the memory viewer, pick that then scroll down to address 000100. At that location on a working cart/board you should see "NEO-GEO" on the right as seem below

IMG_0474.jpg


If there is a data/address issue between the board/cart the NEO-GEO will be corrupt. What the corruption is can point to whats causing the problem.
Click to expand...
 
Thanks for the information.
I started looking at UNIBOIS 4.0 under "MEMORY MAP" yesterday. I didn't know what to look for, unfortunately there is no working board. I'll look again tomorrow.
so should I go to 000100... if I see the inscription "NEO-GEO", what does it refer to?
 
That "NEO-GEO" is part of the header on the program rom on the cart. Getting crosshatch with a cart inserted indicates there maybe a data/address issue for the board talking to the program roms of the cart. If there is some data/address issue it will likely cause that "NEO-GEO" string to be wrong in some way.
 
unfortunately, I could only extract data from slot 2.
if I put the card in slot 1, the screen is black.
If I understand correctly, there is something wrong with the mvs Board. What should I do now?
 

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If you compare the expected NEO-GEO with your LEM-EEM it points the were the issue is.

Code: 
       HEX          |  ASCI
-------------------------------
4E45 4F2D 4745 4Fxx | NEO-GEOx
4C45 4D2D 4545 4Dxx | LEM-EEMx
 ^    ^    ^    ^     ^ ^ ^ ^
Then converting the hex values into bits you can see the specific bit that is causing the problem

Code: 
 HEX |       BITS
------------------------
4E45 | 01001110 01000101
4C45 | 01001100 01000101
             ^
4F2D | 01001111 00101101
4D2D | 01001101 00101101
             ^
4745 | 01000111 01000101
4545 | 01000101 01000101
             ^
4Fxx | 01001111 xxxxxxxx
4Dxx | 01001101 xxxxxxxx
             ^

So looks like data bit D9 is stuck low.
 
Unfortunately, I don't understand the bits. Therefore, unfortunately, I don't know what you wrote means.
I don't have the knowledge for it.
I don't know where to start in discovering the error.
I started to check the D9 Data line, on the M68000, leg 60. It is not at a low level.
here I realized that we are not thinking the same thing.
:(
 
ack said:
You are almost there. The D9 data line between the cart slot and the CPU is not direct. It will got through the NEO-G0 to the left of slot 1. This IC is picking which of the 2 slots data lines will be passed to the CPU.

https://wiki.neogeodev.org/index.php?title=NEO-G0
https://wiki.neogeodev.org/index.php?title=File:Neo-g0_J4_pinout.png

I would also verify you are see the same issue with multiple carts. Its always possible the issue is the result of a bad cart.
Click to expand...
I have 2 test cards. both worked. both write the same code for 100 addresses "LEM-EEMx". the card is not at fault. I also started looking at the NEO-G0. is in contact with the CPU. Tomorrow I will replace it with another NEO-G0. We'll see what he does.
 
r67055 said:
I have 2 test cards. both worked. both write the same code for 100 addresses "LEM-EEMx". the card is not at fault. I also started looking at the NEO-G0. is in contact with the CPU. Tomorrow I will replace it with another NEO-G0. We'll see what he does.
Click to expand...
Before you swap I would verify continuity between the slots data lines and the NEO-G0. It could always been a corroded/cut trace.
 
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