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Author Topic: A4000D u212 gal  (Read 500 times)

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Offline gary2000Topic starter

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A4000D u212 gal
« on: November 18, 2017, 08:38:46 PM »
Would anyone know where I could purchase a programmed u212 gal 22v10b?


I thought I'd try and repair this board one more time. I probably should just put amibian on a Raspberry Pi and stop torturing myself though. :)
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Offline klx300r

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Re: A4000D u212 gal
« Reply #1 on: November 18, 2017, 09:35:22 PM »
Quote from: gary2000;833295

...
I thought I'd try and repair this board one more time. I probably should just put amibian on a Raspberry Pi and stop torturing myself though. :)


joy/ pain, peace/ torture...amiga/ emulation

I’ve literally cried when trying to get my 1200T/ Mediator setup working and rejoiced when she finally was humming...many many Amiga projects later and the cycle continues, you have to love something before you can hate it & love it again..ONLY AMIGA :laugh1::furious:
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Offline gary2000Topic starter

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Re: A4000D u212 gal
« Reply #2 on: November 19, 2017, 01:45:24 AM »
so true.:)

My original 2000 was easy to fix by buying an NOS motherboard years ago. The 500 did not have a battery to leak, except on the memory expansion.

But this...
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Offline wmaciv

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Re: A4000D u212 gal
« Reply #3 on: November 19, 2017, 03:08:48 PM »
@klx300r
 
 "you have to love something before you can hate it & love it again..ONLY AMIGA"
 
 Truth.  This need to be a sticky on every Amiga board...
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Offline gary2000Topic starter

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Re: A4000D u212 gal
« Reply #4 on: November 19, 2017, 05:45:49 PM »
They make PLCC28 To DIP 28 adapters, so maybe I will try one of these to program it, if I find the file.
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Offline gary2000Topic starter

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Re: A4000D u212 gal
« Reply #5 on: November 19, 2017, 05:50:43 PM »
By the way, this is what I have to work with...
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Offline Castellen

Re: A4000D u212 gal
« Reply #6 on: November 19, 2017, 05:55:19 PM »
Quote from: gary2000;833295
Would anyone know where I could purchase a programmed u212 gal 22v10b?




I can supply one - send me an Email if interested: http://amiga.serveftp.net


Out of interest, what's the fault you're seeing to reach the conclusion that U212 is bad?  The device is mainly generating column/row address stobes for the chip memory DRAM.  So if you're seeing valid clock and strobe inputs but seeing no column/row address stobes out (they should be there all the time regardless of what the A4000 is doing), then I'd agree it would be a U212 problem.

It's not that common for this part to develop problems.  In 20 years of repairing A4000s, I don't recall ever seeing U212 needing replacement.  That's not to say it can't fail of course.


Edit:
Just saw the photo (don't know why the A.org photo attachments only show as 'error' with IBrowse).  Obviously lots of corrosion damage, and missing pads at U212.  Did someone mistake a sledge hammer for a SMD rework station?   :hammer:

Unless U212 has been visibly corroded, it probably won't have a problem.  The missing pads can be fixed without too much trouble.  And given that there's not much left of anything real time clock related, I'd suggest leaving it out completely.  The system will run fine without U177/U178.  You'll need U976 working to some extent, as the system software looks at the two lower bits read from this to determine you have the AGA chipset.  Else you'll only get ECS screenmodes if you eventually get it booting.  And check that MDAT from U975 pin 13 is connected to where ever it should on Lisa, else if the input at Lisa is floating then it won't generate certain clocks and the system won't boot at all.
« Last Edit: November 19, 2017, 06:26:59 PM by Castellen »
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Offline gary2000Topic starter

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Re: A4000D u212 gal
« Reply #7 on: November 19, 2017, 11:47:58 PM »
Thanks for taking the time to look over the picture. Yes this thing is a disaster and I'm no expert, but have cleaned it up quite a bit believe it or not.

I don't believe it can start up without u212, correct?

May fix the pads and see what I can do with u212. Just want to give it some thought and may contact you for a new one.

I agree, it will never have RTC again, but that's okay.

The back of the board is just as pretty. At this point, I don't care what it looks like but we be thrilled if it could work in any capacity.  

Quote from: Castellen;833335
I can supply one - send me an Email if interested: http://amiga.serveftp.net


Out of interest, what's the fault you're seeing to reach the conclusion that U212 is bad?  The device is mainly generating column/row address stobes for the chip memory DRAM.  So if you're seeing valid clock and strobe inputs but seeing no column/row address stobes out (they should be there all the time regardless of what the A4000 is doing), then I'd agree it would be a U212 problem.

It's not that common for this part to develop problems.  In 20 years of repairing A4000s, I don't recall ever seeing U212 needing replacement.  That's not to say it can't fail of course.


Edit:
Just saw the photo (don't know why the A.org photo attachments only show as 'error' with IBrowse).  Obviously lots of corrosion damage, and missing pads at U212.  Did someone mistake a sledge hammer for a SMD rework station?   :hammer:

Unless U212 has been visibly corroded, it probably won't have a problem.  The missing pads can be fixed without too much trouble.  And given that there's not much left of anything real time clock related, I'd suggest leaving it out completely.  The system will run fine without U177/U178.  You'll need U976 working to some extent, as the system software looks at the two lower bits read from this to determine you have the AGA chipset.  Else you'll only get ECS screenmodes if you eventually get it booting.  And check that MDAT from U975 pin 13 is connected to where ever it should on Lisa, else if the input at Lisa is floating then it won't generate certain clocks and the system won't boot at all.
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Offline Castellen

Re: A4000D u212 gal
« Reply #8 on: November 20, 2017, 05:49:16 AM »
Quote from: gary2000;833347
I don't believe it can start up without u212, correct?



Definitely it cannot work without U212.  No idea exactly what it would do, but best case you'd get a green screen error as the initial ROM memory test would detect the memory problem.  You need some working chip memory for the system to run.  And there's no way the chip memory can work without column/row selection - which is the job of U212.

The part you have now is probably OK, unless it's visibibly damaged.
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Offline Acill

Re: A4000D u212 gal
« Reply #9 on: November 21, 2017, 02:38:16 PM »
If your not in a big rush I can repair those pads. I dont think I can get to it before the new year though with work travel and the holiday.
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Offline gary2000Topic starter

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Re: A4000D u212 gal
« Reply #10 on: November 24, 2017, 04:56:57 PM »
Thank you, I will keep you in mind. In my spare time I'm evaluating the board, as I have found acid has eaten away legs of other ICs.

This is such a poor candidate. As I look at it, I wish that I had acquired it sooner.
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