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Irem M72 Dragon Breed PCB

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Monstermug View Drop Down
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    Posted: 18 Apr 2017 at 2:08pm
Think I got lucky with this fix. 

The problem I had was there was graphics glitches.  This board had been sent to Phil before so before I started working on it, I had asked him just in case he knew what might be the cause of it.  As I didn't expect him to reply instantly, I decided to do a bit of investigation myself.


As you can see the dragons tail is not missing but draw in the middle of the screen rather connected to the head.  In fact it was isolated to this middle section of the screen. 


Also some of the sprites characters were missing on the animated section of the dragon breed logo as shown above.  (Also noting that the missing sprites were in the same vicinity)

As I have heard, M72 boards are notoriously difficult to work on so I spent some time to analyse the problem as doing so could help me isolate the problem and save hours of chasing tails.


From the glitches I can see that it's definitely something to do with the sprite circuitry as background and foreground graphics are fine as shown above after the animated section of the dragon breed (sprite controlled).  Also in game background and foreground graphics looks fine.  Roms are unlikely to be the culprit here but as it was so easy to verify roms, I did this to confirm this to be true.

Next step was to isolate which boards were the cause of the problem.  Lucky for me I have many M72 games and swapping boards isolated the problem to the main board.


The big board in the middle is the main board.  It contains 6 customs chips with loads of buffers and other circuitry. 

Normally I would take my probe out and start probing the address lines of the rams but because the CPU was connected to the top layer board this was impossible to do.  I had thought about using some DuPont wires to separate the top boards but I didn't have enough of them!  It uses two 50 idc connectors which I didn't have any either.

I manually traced the Sprite roms back to Custom chip KNA72H010 914) @ C46 and this goes out to some buffers to a bank of ram @ C53-C58.  I deduced that the this custom chips replaces many of the addressing circuitry for the sprites and that the bank of rams were sprite rams.  I think this customs also controls some of the sound effects too.

Lucky for me these bank of rams were all socketed from a previous repair.  I knew not all of them were bad, maybe just one if not just a few, judging from the glitches I had observed from the start.  Swapping the main banks of chips around I got nothing until I started swapping out Rams @ C53/54.  These caused the glitches to change!


Got the dragons tail back but some other sprites corruption elsewhere. 

I didn't have any spare 6116 chips so I ordered some. 

At this point I got an email from Phil confirming it could be the ram (or custom chip that's at fault) so I was pretty assured that this was the fault.  Many days later (today) a bunch of 6116s arrived.


Put two new Rams in at location C53 and C56 (was previously located at C54) and got a perfect picture.  I decided just to replace all the ram as I have many 6116 rams now =)



Without any further glitches I deemed this one another successful fix!

Think I got lucky with this one being that it was not a custom that was the problem.   They aren't easy to get hold of and can be quite expensive to if you can find one. 

I'm a happy fella. LOL







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Post Options Post Options   Thanks (0) Thanks(0)   Quote Alpha1 Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr 2017 at 2:23pm
Awesome work dude!

I've got a dead Dragon Breed PCB somewhere I can send you if you want haha.
Wanted: Time Traveller, GALAXIAN 3 THEATER, 80's Namco & Taito games

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Monstermug Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr 2017 at 3:00pm
Originally posted by Alpha1 Alpha1 wrote:

Awesome work dude!

I've got a dead Dragon Breed PCB somewhere I can send you if you want haha.

Sure buddy can do.  Only if it doesn't have rust on it.  I don't do rust Ouch
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Maskman Quote  Post ReplyReply Direct Link To This Post Posted: 11 Nov 2019 at 4:05pm
Hi,

I own this game on M72, and my issue is no sprites, only backgrounds and sound. See the below video :

https://youtu.be/JxsQ9B8ALOc

Could you please help me to know where to check ? I’m not a specialist !

Thanks
Regards
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Monstermug Quote  Post ReplyReply Direct Link To This Post Posted: 11 Nov 2019 at 4:40pm
Check if the roms are good first.  May just need a good reset.  Check Ribbon interconnect cables.  If they are all good then it's either custom KNA72H010 @C46, buffers or the bank of ram C53 - C58.  You also have jail bars for the background too.  Break out logic probe and check address lines and enable lines.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Maskman Quote  Post ReplyReply Direct Link To This Post Posted: 11 Nov 2019 at 5:16pm
RAM NG 10, ROM OK ! How to reset ? Don’t have the doc.
I check the RAM on the bottom board’ and there is nothing weird, but don’t have a tester.
Don’t have tool for checking probe or address lines, don’t know where the are in the 3 boards !

I found this below for R-type

https://www.arcadefraidi.com/repairs/rtype-irem-m72/?unapproved=48&moderation-hash=e85842a088850aaf77b9f64bf7cf7b90#comment-48

Edited by Maskman - 11 Nov 2019 at 5:20pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Monstermug Quote  Post ReplyReply Direct Link To This Post Posted: 11 Nov 2019 at 5:45pm
RAM NG 10 are the sprites rams on the middle board.  So you have to remove the top board and you will find the banks of ram on the middle board.  But if you have no tools to repair it, I recommend you send it to someone who can.  It's an expensive game so worth it. Iirc they are 6116/2018 rams.  I've got plenty of those.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Monstermug Quote  Post ReplyReply Direct Link To This Post Posted: 11 Nov 2019 at 8:52pm
IC21, IC22, IC23, IC24, IC36, IC37, IC38, IC39 are the ones you need checking.  Luckily some of them are already socketed so you can try swapping them around to see if any graphics have changed.  The ones in bold are the same ram as the others.  Like I said you will need to probe them to find out which is faulty.  You can also try piggybacking the ones in bold to see if anything changes but you can't do that if you don't have any spare 2018/6116. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Maskman Quote  Post ReplyReply Direct Link To This Post Posted: 11 Nov 2019 at 9:08pm
Ok, thanks. How to probe, and which tool I have to use ?
What is the spare 2018/6116 ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Monstermug Quote  Post ReplyReply Direct Link To This Post Posted: 11 Nov 2019 at 9:27pm
tbh if u didnt understand that you should ask me or someone else to take a look at it for u. id hate to see the aftermath of you trying to repair a £400+ pcb.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Maskman Quote  Post ReplyReply Direct Link To This Post Posted: 11 Nov 2019 at 9:36pm
Originally posted by Monstermug Monstermug wrote:

tbh if u didnt understand that you should ask me or someone else to take a look at it for u. id hate to see the aftermath of you trying to repair a £400+ pcb.


It’s just curiosity ! I plan to let a specialist repair it !

Edited by Maskman - 11 Nov 2019 at 10:39pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Maskman Quote  Post ReplyReply Direct Link To This Post Posted: 13 Nov 2019 at 8:44pm
Hi,

I used the middle board of my "Air Duel", and the RAM OK, ROM OK !!! But stocked on it nothing happen

There something to do, like clear the Ram/Rom, something like that ?

Thanks





Edited by Maskman - 13 Nov 2019 at 8:54pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Monstermug Quote  Post ReplyReply Direct Link To This Post Posted: 13 Nov 2019 at 9:44pm
Then you have problems with either top or bottom boards as well.  You can't just swap roms around to test either.  There are jumper settings you need to configure as well.  it's different on each game.  

This is the jumper settings for Air Duel 



and these for dragon breed.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Maskman Quote  Post ReplyReply Direct Link To This Post Posted: 13 Nov 2019 at 10:02pm
Yeah ! The dip test was activated ! Now it working !!!
The issue is definitely on the middle board that need to be checked ! There is still the vertical line issue !

https://youtu.be/lEKRk_Pe_IQ
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Monstermug Quote  Post ReplyReply Direct Link To This Post Posted: 13 Nov 2019 at 10:48pm
....but I already said that Ermm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Maskman Quote  Post ReplyReply Direct Link To This Post Posted: 14 Nov 2019 at 11:11am
Originally posted by Monstermug Monstermug wrote:

....but I already said that Ermm

Yes ! Do you know how much doesn’t these RAM series cost ?
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