Nintendo Vs PCB Repairs

[Hooligan93]

Hi everyone,

Awhile ago I bought a lot of 3 Vs boards untested.  I built a Jamma adapter ( no inverted video circuit though) to test boards. All boards were not working when used with a verified SMB Pak with the right PPU and CPU and verified Roms with eprom programmer.

The first board (MDS-04-CPU) started up with a blank screen.

Second board (MDS-05-CPU) Started with a blue screen.

Third board (MDS-02-CPU) Started with a yellow screen. Lots of corrosion on this board as well.


The first board i decided to fix first as it was in the best condition and the pcb version was the same as my working board. Tested Voltages all good. Reset CPU and PPU a few times. No luck. Reflowed sodder on CPU and PPU sockets. Still no luck. Replaced Sockets with dual wipe sockets.

BY this time I bought another PPU and CPU with tennis Roms. The  Tennis roms were corrupt so burned Tetris instead. Tested good on known working PCB. Put these into test board. Test board booted up into Tetris but was resetting about every 5 seconds and had corrupted graphics. Spent about a week tracing and testing data lines from the Roms and Ram with no luck. Was frustrated and put SMB back in with the dummy CPU and it came to life with no graphics problems.

Put back in good board and it stared giving problems like the test board. Re-verified roms checked out good on all. Swapped PPU with SMB worked no graphic corruption but colors were different.

In the end I believe swapping the sockets was all that was needed. Read somewhere if daughter boards are used then removed, the pins are larger then regular CPU pins and cause sockets to make poor contact with PPU and CPU.


I will update this thread as I work on the other 2 boards.

[LovelyCoCoNuts]

Some great info here. Thanks for sharing

I have a vs board i got in a lot as well. So nice to know.

Is there a schematic for a video invertor circuit?

[Hooligan93]

There are some DIY instructions and schematics to build a video inverter board on Mike's Arcade.

https://www.mikesarcade.com/cgi-bin/spies.cgi?action=url&type=info&page=mixedbag.html

But, if you get the Jamma adapter it is built into it along with an audio amp. I like the one from Cambridge arcade as it has a video switch to allow you to play both sides of a Vs board with one monitor, and its $10 less then Mikes adapter. This is the one I'm going to get eventually for my bench test rig.

http://cambridgearcade.dyndns.org/?q=node/38

[Hooligan93]

UPDATE

I got my second Vs board (MDS-05-CPU) up and running.
When i powered it up it would show a blue screen and out of sync.
Checked voltages they were all good.
Checked CPU reset pin all good was staying high.
Checked clock line on CPU seemed good.
Checked Data lines and they were all chattering away or so i thought.
Started to check data lines on program Roms all good, but no activity on graphics Roms. The read write pins stuck high all the way to the CPU.

Wasn't sure what to do so decided to tackle the sync issue. Thinking this had to do with clock signal traced it back to the CPU. Found at pin 31 a timing signal is outputed to 5E which was a 74ls04. I just happened to have one loose so i piggybacked it. I got picture but still out of sync. All the data lines on the graphics roms were now chattering away.

Now I knew the only thing left was the sync, and it was at 1L another 74ls04 grabbed one off the corroded board and piggybacked it on 1L. Screen went white. looked at chip it was a 74F04. swapped it with the one piggybacking 5E and the board came to life.

Pulled the bad chips off but accidentally pulled off 2k instead of 1L. Doh. Socketed 1L, 2K and 5E. Put 2k into 5E just to see if it works and it was bad as well but only affects second side of Vs board.

Wow 3 bad 74ls04 on one board and nothing else wrong. Something must have happened on the clock line out of the CPU in the past.

FYI I found 2 faulty 74ls04 off the corroded 3rd board (MDS-02-CPU). These chips may be a really susceptible to failure on these boards.

[Aztarac]

I agree about bad 74ls04's on these boards.  I had a board that was missing all the moving sprites on one side - turned out to be a bad 04.

What are your thoughts on this issue I'm having:

Revision 4 board - The left (main) side of the board (looking at it with the edge connectors on top) is displaying a white screen, however, the game boots up and will 'play'. You can start a game and hear the game sounds as the joystick and buttons are used. The right (sub) side of the board works fine.

Posted this to KLOV as well, but just got a response to check the connector and wiring, even after I explained in the thread that there are no issues with the wiring, power supply, monitor, etc.  I have 2 other boards that work just fine in the game.

[Hooligan93]

I am by no means an expert on this, shout out to Adam excelent PCB repair videos.

If game is playing blind, then I would expect The CPU, PPU, Roms, and Ram are all good.

I would start looking at the video section of the schematics. 1P and 3P (LM324 op-amps) and 2P and 4P then the transistors at Q13, Q14, and Q26(should see middle leg pulsing), If still nothing only part left is PPU legs 14,15,and 16 or damaged trace in between.

Good luck let us know what you find out.

[Aztarac]

Thanks for the guidance - much appreciated!!  I'll do some testing and let you know what I find.

[Hooligan93]

Update

Started working on second sides of boards.

Working board works on both sides.

1st board MDS-04-CPU right side working, left side blank screen
2nd board MDS-05-CPU right side working, left side blue screen.
3rd board MDS-02-CPU Have been using for parts to fix and test the other boards. Have some parts ordered to replace.

Started working on MDS-05 board, put set of roms (pinball) PPU and CPU in left side of board with SMB in the right side. Didn't work at first then realized i had put a dummy CPU in swapped it out with a RP2a03E came to life for a minute but was out of sync then went to a blue screen. CPU is not resetting seems like video signal is leaving the PPU so may have problems in the op amps and or sync signal. Switched video to right side of board and is working but no sync. Pulled CPU out of left side no change, pulled PPU and video came back to right side of board with no sync problems. One step forward two steps back. Out of 74ls04 and LM324 will have to wait for parts to come in.