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Sega Outrun Sound Issue


Boots

Question

Hey guys, need some help with the sound on my Outrun.

When I turned it on yesterday all seemed good except only the background music and a few other sounds like the traffic lights were working.

All the speech and the car sounds are missing.

There is a slight crackle on the speakers that appears to coincide with the timing of the sounds.

 

I assume it's in the top board, not in the separate amp board as I believe the sounds are mixed prior to going to the amp??

Any suggestions?

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OK, so I think I have narrowed it down to one area of the board (see pic)

outrun sound.JPG

I removed the roms IC66 through to IC71 and no change, still only the music and the coin up, signal sounds working.

So I guess it is likely to be the 2015 RAM or the 74LS137???

Is there something I can check to confirm?

Help here would be appreciated I would like to get this going for my nephews for Xmas day.

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You have tried re-seating the socketed chips haven't you. Those and the individual board connectors were about the only things I ever had dramas with on Sega boards other than coke being spilt over the top boards in Daytonas and Sega rallys etc. You may also like to check the power supply voltages on each board. The voltages can vary between the boards and don't assume it is a sound issue. It may be a sound select issue on another board or part of the board. What happens when you put the machine into sound test mode?. Not sure if Outrunner had this though but in the other Sega drivers you could test individual sounds and speech phrases.
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You have tried re-seating the socketed chips haven't you. Those and the individual board connectors were about the only things I ever had dramas with on Sega boards other than coke being spilt over the top boards in Daytonas and Sega rallys etc. You may also like to check the power supply voltages on each board. The voltages can vary between the boards and don't assume it is a sound issue. It may be a sound select issue on another board or part of the board. What happens when you put the machine into sound test mode?. Not sure if Outrunner had this though but in the other Sega drivers you could test individual sounds and speech phrases.

 

Yep removed all the IC's and reseated

It does have a test mode and when you test the non-working sounds you just get a faint crackle so I assume it is trying to play the sounds.

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Check the 12 volts. On many power supplys, turning up the 5vDC robs voltage from the 12vDC supply. Segas use 12 volts for the sounds. If the 12 is to low, you may be needing a new power supply with a strong 5volts and healthy 12volts.

Checked voltages all good

I have some ram on order, looks like I will be digging that out when it comes in

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Well I am still stuffing around trying to sort this out. @Womble has been a great help with amazing patience and hopefully I am nearly there.

So far I have replaced the 2016 ram (IC91 & IC92), the 74LS137 (IC112) with no improvement.

Poking around the amp there seems to be everything ok there so there is not too much left except for the 100 pin surface mount IC90 and the 16mhz crystal.

Checking the crystal output to IC90 it reads as high with my logic probe and 5v with my multimeter, comparing this to the 40mhz crystal in the other section I get a pulse reading and around 1.1v.

Does this sound like the possible cause of it all?

 

[EDIT]

I just realised I misread the schematic, pin1 of IC90 is the crystal not pin100, checked pin1 and it looks ok.

Thought I had something there :(

Edited by Boots
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