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System 16 motherboard


cal2

Question

:cool:Following the repair of the golden axe rom board, I am now on trying to repair the faulty system 16 motherboard.

 

The symptoms are:

 

- Bad scrolling

- No sound

 

I suspect the ram chips used to store the scrolling data, but not sure. Also, the AMP used the motherboard may be defective.

 

[update 1]

 

the UDP7759 reset line is stuck low. It should be high. Don't know yet what chip is involved in the reset of the UDP.

The amplifier is good. It simply has no sound to amplify from the YM3012, YM2151 and UDP7759...

Edited by cal2
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Always worth suspecting the RAM first. Are there any GAL chips on the board? I know there are half a dozen on my System 18 board but cant remember whats on a 16. I had weird issues on my Sega 18 which was solely down to the GALs being in the wrong sockets, correct chip type, but wrong contents for their location.

 

If you put the board into service mode you should be able to get it to test the onboard RAM for you, tho some of the tests are not very indepth.

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Thank you for the informations ! I didn't know there is a test mode on system 16. I quickly tested it before going to work this morning. Not very easy because the characters displayed are wrong, but I was able to run at least the program rom check and all are ok. I will run the other parts of the self test later and see if there is a problem.

 

However I am not certain this is a vram problem because when I put a finger on the rom board connector for the scroll data, the display changes and sometimes I can see the correct graphics... I suspect some glue logic chips are bad and some pins are floating which could explain why puting a finger on the connector changes the display.

 

Any idea how to find these chips ?

 

thank you,

david

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