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Scramble bootleg not coining up

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Category: Technical
Forum Name: Tech, Maintenance & Repairs
Forum Description: Need Help? Ask Here
URL: http://www.ukvac.com/forum/forum_posts.asp?TID=360817
Printed Date: 17 Nov 2017 at 10:55pm


Topic: Scramble bootleg not coining up
Posted By: Lurch666
Subject: Scramble bootleg not coining up
Date Posted: 13 Nov 2017 at 4:39pm
I've decided to start a new thread since this is just going to be about my scramble boot.
In the thread below I covered how I got this board in a working condition:
http://www.ukvac.com/forum/promskung-fu-master-and-scramble_topic360085.html" rel="nofollow - http://www.ukvac.com/forum/promskung-fu-master-and-scramble_topic360085.html

However I only had the jamma adaptor wired for power and video.
I have added connections now for coin up,player one start and the speaker so I could test the sound but it will not coin up.
I have also set the dip switched to free play and tried the service mode but neither of those work either.Even with the dip set to free play it still says credits:0 at the bottom of the screen.

The board is also unstable.To get it to boot up I have to increase the 5V line to over 5V then bring it down to as low as it can go (about 4.5V).
Then I have to power cycle it and it will run but after about 5 mins it starts to glitch then crash.It refuses to run on anything over 4.5V
I'm thinking this is something to do with the electrolytic caps but wanted to test the sound first.
I have probed pin 37 if the 8255 at 1E that receives the coin up signal and its going low as it should.The other pins seem to be active as well.
The other 8255 at 1D isn't showing much activity but I don't know if that's normal if the game isn't actually being played.
Swapped the Z80 with a known worker and that made no difference.

Going to keep looking but any suggestions would be welcome.


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You rang......?



Replies:
Posted By: andrewsm
Date Posted: 13 Nov 2017 at 6:08pm
Hey, Ive seen many 8255 chips with faulty ports. Try replacing chip for starters.

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WANTED: Any Nichibutsu stuff, Pre Jamma Fan. scrap nichibutsu table
http://www.arcadetester.co.uk" rel="nofollow - http://www.arcadetester.co.uk


Posted By: Lurch666
Date Posted: 13 Nov 2017 at 7:23pm
Thanks for that.
Ordered some 8255s but the ones in the UK were a bit too expensive so I get 5 from china for about £6.
Will update when they arrive (unless I figure something else out before then).


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You rang......?


Posted By: philmurr
Date Posted: 13 Nov 2017 at 8:20pm
You could try swapping the positions of the 2 8255’s and see what you get. Although the 8255 at 1D does drive the protection so the game may just crash depending on what version of software you’re using.


Posted By: Lurch666
Date Posted: 14 Nov 2017 at 9:47am
That's a good idea but both need desoldering.I was hoping to just desolder one and swap it with a new chip to try and get out of doing both but I might do both anyway.
But first I have had another idea.As mentioned in the other thread I got amidar running on this but it was coining up,starting a game and constantly pressing fire.I was puzzled at this behaviour as I have non of the buttons wired up.
Now I know that the 8255 are programmable I'm thinking the version of the games are programming them wrong.I will go back to trying other versions of the scramble roms (there are a few I haven't tried yet) to see if I can get a version that runs and coins up.


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You rang......?


Posted By: Macro
Date Posted: 14 Nov 2017 at 1:39pm
I don't think they are programmable in the sense of MCU's - they don't execute any program code. It just means you can change which set of IO ports are being used under program control - the CPU only writes one byte at a time.

If it runs for a little while, I'd start by checking for any hot chips (some chips, like the SRAM for the sprite buffers run hot anyway, but most others should not) - n.b. be careful, using your finger seems like a good idea, but some chips (I still remember a Pentium 90 where the heat sink fan had failed) get hot enough to burn your skin!



Posted By: Lurch666
Date Posted: 14 Nov 2017 at 6:18pm
Maybe programming was the wrong term to use.I'm guessing that it's like an arduino where the inputs and outputs can be used for various things that are defined by the code running on the board.
Maybe one version of scramble expects the coin up to send pin 37 of the 8255 low where another version expects player one joystick up to put pin 37 low.

Actually typing that has given me the thought that if I send all of the non power/video pins of the (non) jamma edge connector to ground maybe one of them could cause a credit to appear.


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You rang......?


Posted By: Macro
Date Posted: 14 Nov 2017 at 6:38pm
certainly worth trying coin1 / coin2 and service - all should give credits (depending upon dip switch settings) - or just put it into freeplay!

Dip sw.
--------     
    1  2  3  4   5  6  7  8   Coin  Play
-----------------------------------------
    -  -  -  -                 1     1
    +  -  -  -                 1     2
    -  +  -  -                 1     3
    +  +  -  -                 1     4
    -  -  +  -                 1     5
    +  -  +  -                 1     6
    -  +  +  -                 1     7
    +  +  +  -                 2     1
    -  -  -  +                 2     3
    +  -  -  +                 2     5
    -  +  -  +                 3     1
    +  +  -  +                 3     2
    -  -  +  +                 3     4
    +  -  +  +                 4     1
    -  +  +  +                 4     3
    +  +  +  +                 Free Play



Posted By: Lurch666
Date Posted: 15 Nov 2017 at 4:54pm
My scramble manual (the one available on the net) has dip 1&2 off for freeplay but have tried it both ways and it still says Credits:0.
I'm presuming it says free play when the dip switches are set correctly.I can't check on mame as the free play option seems to be missing (0.188).
Also tried grounding one by one all the other pins on the 8255 (that handle player movement,fire and all the other buttons) but got no sign of life.Since the dip switches also work through this chip it's looking duff unless I have the wrong version of scramble but:

Spent a day of erasing and flashing eproms (why does this one need EIGHT program roms) and this is what I found.

The roms named s1.2d to s8.2p that appear in most of the versions of scramble in mame are all identical and produce the boot loop where I get the grid then the score appears at the top,the grid clears except for the squares level with the scores then it goes back to the grid filling the screen again.(there's a video of it near the end of the first page in the last thread).

Stearn scramble set1 roms scrambles.zip 2d-2p just gives me garbage.Does not even get to the grid.
Stearn scramble set2 roms scrambles2.zip 2d-2p gives me the boot loop again.

scramble (bootleg) scram2.zip roms r1.7f1-r5.1l gives screen of characters moving that looks like a test pattern then 'BAD ROM'-checked all the roms including the sfx roms but couldn't get past this.

Scramble (bootleg on galaxian hardware) scramblb.zip scramble.1k-scramble.3j gives just a grid.

Scramble (bootleg?) scrambleb.zip roms 1-8
Bomber (clone) bomber.zip roms 1.3l-8.3a
Strafe bomb (clone) strfbomb.zip roms 1.2c-8.2p
All run but will not credit up.

So either I have a super rare bootleg that doesn't have the correct roms on mame (doubt it) or I will be doing a LOT of desoldering soon.




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You rang......?


Posted By: PaulSwan
Date Posted: 16 Nov 2017 at 3:34am
From the pictures on your prior thread, it appears you have the MU-1 top (with a Zaccaria serial number) and a Konami original bottom with Stern ROMs. At least your set is mismatched in that respect.

Zaccaria officially licensed both Scramble & Super Cobra and I've seen them run either Zaccaria boards or Konami. I'm not sure what game might have been on an MU-1 set with a Zaccaria label. Possibly some other game, maybe Amidar.

If you haven't already, check the underside of the boards for wire-strap hacks that might indicate a conversion. There are hacks that move the interrupt pin and shift the ROM addresses around for other games.

Paul.


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ZZZ


Posted By: Lurch666
Date Posted: 16 Nov 2017 at 10:33am
The only mod is the one near the dip switches on the smaller board.there are a load of yellow and orange wires that I thought were standard but I have just googled some images of the same board to find those appear unique to mine.Will now have to check the schematics to see what they do.Thanks for the info dude.

EDIT:After a quick look it seems that those wires just tie the player one and player two controls together so both can use the same joystick.

I have desoldered both 8255s but got a bit clumsy with the first one (1E) and it didn't survive.
I tried the other one at E1 once I removed it but no difference but that one could be faulty as well.


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You rang......?


Posted By: obcd
Date Posted: 16 Nov 2017 at 8:08pm
The 8255 chips have different modes of operation, but likely they are set to generic io which means the cpu has 3 registers that read the status of the 3 I/O ports. If the cpu writes to it, it can set the bits of the I/O ports high or low. Those chips are pretty basic as they are rather old.



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