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Super Monaco GP Airdrive

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sega_man

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I have this game, sat in the garage for years. Now it boots to just lines on the screen. I've cleaned all the socketed chips but no change. The 5V rail is only showing 4.5v so was planning on removing the PSU & recapping, worth trying to adjust the 5V voltage first? The guy I know of who used to fix these boards no longer does, apparently the custom chips tend to fail & they aren't available :( Any help would be great! Thanks
 
yes, try adjusting to 5V to see if it helps but if the ps is really bad, it will quickly fail so I would do it disconnected from the board first to make sure it doesn't bump to 8v or something!
 
Good thinking! I'll adjust off the board 1st and see what happens. Wish me luck please ;)
 
OK, with no board I could get spot on 5V. With the board connected I got 4V, could only get this to 4.7V, do we think that would be low enough to cause non booting and lines all over the screen? Recap the PSU?
 
Well since you have the worthy deluxe version and you seem to want to make it live again, yes, changing the caps is a good idea. Will it solve the issue? probably not. but you won't know before you try right? Will 5v make it boot? I don't know either but if it's just that 5Volt, you could try a computer PS if you have one and see if it's 5v is good and if it's still not booting, you'll have saved on caps.

There's a bunch of other things you have checked right? fuses and all ? manual
 
Fuses are all good. I've tried another set of ROMs I had from an old board that died but that made no difference. As the game has an inbuilt test mode I could really do with knowing what is required for that to work? ie, would a bad RAM chip prevent the test mode from starting? I think all I can do is get the PSU supplying 5V and take if from there. Be a real shame if it can't be fixed :(
 
I've got the caps on order, at least when I know the power is good I can start! I did find this interesting info : -

Info

Is there anyone on here that could supply 2 EPROM's and burn this software to them for me? Or a company out there that does this service?
 
Hi Sega man.

I have some experience with X Boards and have had some success in repairing. Your first issue is to resolve the power supply problem as indicated by @Mrhide. These boards are voltage sensitive and 4.5v is no where near enough to get them to boot. The Sega Power supplies are only responsible for 5V with the 12V usually being generated by a regulator on the amplifier.

The Sega Power supplies are a good unit and worth repairing but it may be more than a few caps.

The test ROMs that you have linked to are excellent. I have repaired two boards using these ROMs so they are well worth a try if the power supply issue does not address the lack of booting.

I am very keen to see how you go with this machine. Keep us posted.
 
Hi, thanks for the reply @berty. When you say it may be more than the caps what else tends to fail on these PSU's?

Does the board also use 12v? I'll try & find a schematic so I can test that voltage too.

Also, the amp makes a loud hum through the speakers (was like that since the day I got the machine), like a mains hum, any pointers on that would be great!

Good to hear the test ROM's have worked for you, that will be my next step if after sorting the power it still doesn't boot.

Will certainly keep you posted, the help so far from this forum has been great :)
 
I forgot to say, when cleaning it all up I found another issue with the (air drive?) "driver board" (837-7005).

One of the components has corroded legs, marked NEC 2501 905. Of what I can find looks like this may replace it OK?

LINK
 
sega_man said:
Hi, thanks for the reply @berty. When you say it may be more than the caps what else tends to fail on these PSU's?

Does the board also use 12v? I'll try & find a schematic so I can test that voltage too.

Also, the amp makes a loud hum through the speakers (was like that since the day I got the machine), like a mains hum, any pointers on that would be great!

Good to hear the test ROM's have worked for you, that will be my next step if after sorting the power it still doesn't boot.

Will certainly keep you posted, the help so far from this forum has been great :)
Click to expand...

Any number of components in your power supply could be contributing to the low voltage under load. Capacitors are likely culprits but you may also have issue with diodes / rectifiers, large resistors etc.

The main board does not use 12V. So you can rule that out.

Your loud hum may be coming from the amplifier. Sega install AC noise line filters in all of their dedicated machines. It is uncommon for these to fail, but easily replaced. Your buzzing is likely due to failed resistor in your sound amplifier or some other component on the sound PCB. Rebuilding the amplifier and testing passive components like resistors will likely resolve the buzzing.

sega_man said:
I forgot to say, when cleaning it all up I found another issue with the (air drive?) "driver board" (837-7005).

One of the components has corroded legs, marked NEC 2501 905. Of what I can find looks like this may replace it OK?

LINK
Click to expand...

That NEC part is an opto-coupler which is a very common IC used for isolating inputs and outputs. You can purchase cheap testers (around $70USD) OR you can build a simple tester using a power supply, 1K resistor and multi meters. Recommend cleaning the legs with a fiberglass pen and de-oxit before you consider replacing.
 
Thanks again, I'm going to pull the amp boards out now while I wait for the other parts-see if there is anything obvious.

I can't find the NEC part anywhere in the UK? Would either of the ones I linked to be OK? One of the legs fell off when cleaning!

What's best to clean up the ROM sockets? Fiberglass pen? I tried IPA but it didn't get them nice & shiny, replacing all sockets would be a right PITA!!
 
Quick update, PSU is sorted and now has 5v at the board, it still just boots to random lines :(

Next port of call is the test ROMs. I'm thinking bad RAM or ROM?

20220731_115440.jpg
 
OK, big thanks to Gamesmonkey for sending me the test ROM's-VERY much appreciated! The results are in & I'm guessing it's not good news :(

According to the test custom IC's 37 & 41 are failing :(

The others appear to be RAM chips in the same area on the board, could the custom IC fail due to those?

I'm assuming the test IC numbers are correct of course, ie, they match the SMGP board!
 

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