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Fixing an Alcon/Slap Fight PCB

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Judder View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Judder Quote  Post ReplyReply Direct Link To This Post Posted: 22 Jan 2018 at 2:09pm
Originally posted by Mitchell Gant Mitchell Gant wrote:

Do you have access to an EPROM programmer and UV eraser? If so I'm working my way to making a test EPROM that could give a better idea of faults than the built in game test. myPinballs has been helping me test the test Thumbs Up

Definitely and yes if I can share that too that would be perfect!

More than happy to help test the test too!! Clap

Originally posted by Mitchell Gant Mitchell Gant wrote:

I think socketing RAMs like this is always a good idea, as long as you are confident you can do it without damaging the PCB and causing more faults.

Thanks, I'll have a look - I recently got a SMD Hot Air Gun reworking station which I'm yet to try but might be suitable for this - note taken about being very careful...

Originally posted by myPinballs myPinballs wrote:

It would be easier to quote ram and chip as per the board position if possible :) , as this is what the schematics use and how i and Mitchell have been identifying things. The rom names from mame are weird!

Not a problem - the colour proms are (and the weird order is also labelled on the board under the sockets)

ROM 20 - 12M
ROM 19 - 12P
ROM 21 - 12R

I'll talk through any other investigations using those 99X references too to make it easier :)


Edited by Judder - 22 Jan 2018 at 2:14pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote myPinballs Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2018 at 2:31pm
 I've been on quite a journey with my board since the last update.

So my board's video issue is now solved and i can now also (with the std game roms) get passed the zero screen and be presented with a text screen message, so i'm pretty happy right now! No more scratching around trying to rsolve the video sync issue or using the screen flip option to see what's going on.

Both issues of no visable image in std mode and also no text or characters on screen were both related to the same issue. What i worked out after hours and hours of debug is that there is another difference on my board to the schematics. Yes, another modification/slap right change is needed. I found that there was no write enable access to the foreground ram chips and when i traced it back i found some inverter gates and an or gate in the logic. Seems that the write enable line is buffered (possibly for timing needs) and as such looks like this. 



I can draw this up better if you cant decipher the change. The chip at 3D is also used in some logic for the screen flipping. (shown at the bottom of the schematic page)

I also found that this inverter chips was a Fujitu brand and i've had lots of issues with these chips dyeing over time (in many other boards). So much so that it is a known idea to just shot gun all Fujitu ics when you have a bust board!



Anyway, with regular roms i now reliably at power on get to this:




Edited by myPinballs - 25 Jan 2018 at 2:35pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote myPinballs Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2018 at 6:52pm
More updates. I solved my repeating text on screen issues. There was a broken trace on the board for the enable on 3H. Was hard to spot as traces on these boards aren't great quality. What are the other boards quality like? Some bootlegs i've had before are actually pretty good quality but not this one!

Now have this with regular game roms



I'm now at the point of trying to work out why the board is stopping at the ram check ok message and not reporting bad roms or rom check ok message.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mitchell Gant Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2018 at 7:37pm
Ahh, that's excellent progress there. Many thanks for spotting the extra gates in the write signal, no wonder I'm seeing so many problems getting test software to try to run on Tiger Heli when there are yet more hardware differences from Slap Fight.

That extra circuit looks quite crude and asynchronous, using the two inverters at 3D back to back to form a delay. Certainly something that could be very sensitive to timing if it were to be replaced by a more modern 74HCT device, or possibly even a same model chip from different manufacturers.

I'll check my own Alcon PCB later and also double check Tiger Heli to see if it's missing or not there too. 

PCB quality seems OK on my set, but I'll have a closer look now you've mentioned it. I have a single Alcon (Slap Fight) PCB and about 4 or 5 Tiger Helis in various states.

Multiplexer enable fault at 3H would certainly explain the repeating images!

I'll try and look at what could cause the test to halt after RAM CHECK OK if I get chance later.
Boy, is this a machine!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote myPinballs Quote  Post ReplyReply Direct Link To This Post Posted: 21 Feb 2018 at 4:13pm
Quick update on my board repair. I've now solved all the issues with it :) and played my first games a days or so ago. Awesome game.

I had a right journey with it!! Multiple issues on pretty much every section. In summary after getting passed the test screen i had to sort out:

No background tiles
Messed up background tile positioning
Messed up sprite drawing (block patterns)
Nasty sound hum
No controls!

Here are some quick vids of the board running :) Very happy

https://www.instagram.com/p/BfUIIumnYA7/?taken-by=mypinballs

https://www.instagram.com/p/BfYr_BmHOzP/?taken-by=mypinballs

Also found some handy test menus in the dip switch settings

screen test



Live updating dip switch page


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Post Options Post Options   Thanks (0) Thanks(0)   Quote myPinballs Quote  Post ReplyReply Direct Link To This Post Posted: 21 Feb 2018 at 4:19pm
I did some work on the dip switch area and the control switch line caps whilst is fixing some of the faults related to the AY-3-8910 sound generator ic at 11J on the sound/sprite board.

The original boaters had installed nasty dip switches that were too short and too long! Also the caps had all seen better days, so i replaced with MLCC instead of nasty cheap ceramic.

before


after



That brings my repair for this board to a close. On to the next:) I am continuing to help Neil and Alex out and also hoping to work with them to create a high score save solution to for this board set :)



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Post Options Post Options   Thanks (0) Thanks(0)   Quote myPinballs Quote  Post ReplyReply Direct Link To This Post Posted: 21 Feb 2018 at 4:41pm
Next i'm on the hunt for a Hellfire and or Vimana pcb. Some 68000 toaplan goodness :)
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Big Phil Quote  Post ReplyReply Direct Link To This Post Posted: 21 Feb 2018 at 5:26pm
Love your work, Jim!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Judder Quote  Post ReplyReply Direct Link To This Post Posted: 23 Feb 2018 at 3:27pm
I thought everyone might enjoy a few updates from my board testing and the new Test ROM that Neil has been working on

My board set seems to have it's problems with the top 'AUDIO' board - the one with the external connector on it for reference

Neil's Test ROM is clever enough to talk to all the sections of the RAM from the bottom 'CPU' board and identified that it was having problems trying to talk to the Audio RAM that is shared with the second CPU on the top 'AUDIO' board

The way to get the test to function is to dis-connect the board connector nearest the top 'AUDIO' Z80 and then the test can continue with a forced FAIL

Testing the Fujitsu chips on the top board, it turns out that the pair of 74LS138s 3-8 line decoders and one of the 74LS244s that do the memory addressing are failing so my next step is to finish replacing those and see if we get the test ROM to talk to that area of the Audio RAM as well

[and because everyone likes pictures Thumbs Up]



Interestingly the integrated boot test on the actual ROMs hangs at this point too, as it can't return from the RAM check, even though the first reported back result is a ROM test!

Here's the output from Neil's new Test ROM (you can change the colours to make it more readable by removing / adding the 3 colour proms on the top 'AUDIO' board





I'm sure Neil will be along soon with a better explanation of how his clever test ROM works (or will write a technical paper on it judging by the length of the emails Jim, Neil and I have been sending each other!)

More updates as I get a chance to finish the testing....
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