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AuthorTopic: My A2000 restore. Mobo Resocketing fun  (Read 51 times)

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Offline apsteinmetz

My A2000 restore. Mobo Resocketing fun
« on: July 06, 2016, 09:06:34 PM »
Apologies in advance that Google photos won't let me do in-line images.  Lots of PCB porn in the links.

I was pleased to get my old A2000 up and running with a new CF drive, as discussed here.  The rig worked but only because the accelerator card did.  When pulled it out and tried to boot with the stock configuration I just got a green screen. A cursory inspection showed corrosion around the barrel battery, of course.

I tried to pull out the battery and the both sides of the holder snapped off.  Well, now I can see the damage easier!  Obviously, there was corrosion around the battery but I didn't see any spreading around the CPU socket.

The next step was to pop out the CPU.  Uh, oh. Very pretty copper rust on some of the socket springs.  Surprised that the holes close to the battery were okay but, still the socket has to come out.  When I started poking the little spring clips they simply crumbled.. Ugly!  The chip pins had some oxidation on them but I simply scraped them off a bit.

Now I have been soldering since I was 12 but I probably haven't soldered since I was 12.  Taking apart old television sets to get out the giant capacitors for fiendish experiments was my specialty.  I am very grateful for the YouTube videos that gave me the confidence to take a crack at this.

De-soldering 64 pins is a pain in the butt, but a cheapo solder sucker is a miracle worker.  As the YouTube videos show, add a bit of fresh solder then pop the sucker on it.  At first, I didn't know how to purge the solder from the syringe so I started digging into the nozzle to get it out.  Yes, NOW I know that you push the plunger all the way down and a pin pushes it out.  Good example of how the obvious is not so obvious to a rank amateur.  After a couple hours, success!

Now let's look at what's underneath.. Nasty.  The holes closest to the battery have surface corrosion but seem structurally okay.  Again, using the helpful tips from those who have gone before.  I swabbed up the mess as best I could, first with vinegar then, after drying, with isopropyl.  Looks a little bit better  now.

From the photo it looks like some of the corrosion has bled across traces.  Most of that is an artifact of the lighting.  Still, I checked for continuity across all the at-risk traces and found none.  Then I checked to make sure there was continuity from the socket holes to where it's supposed to be.  All good.

Finally, I soldered in a new CPU socket and the coin battery holder from AmigaKit.  Boy, that was so much quicker than desoldering.  Like biking up a hill then flying down it.

Finally, let's pop in a 3.1 ROM and fire it up.  Yay!  Now to put in a "modern" 3.1 environment with my old desktop tools and audio/graphic workstation.

Thanks to everyone on the boards for sharing their experiences or I could not have succeeded!

Epilog: Back in the day before the crazy case mods became a thing in the PC community,  I blinged my A2000 case in my own modest way.  There is this spray paint called "Fleckstone" that gives a faux-granite finish.  I thought it looked way better than putty.  What do you think?  

P.S. Some extra tips that apply generally.  For noobs, by a noob.
1. file off the lip on the plastic power supply connector.  The connector holds firmly to the mobo without it.  That sucker holds on tight!  Slipping and trashing a capacitor when trying to pull it off is a real risk.  Multiple reconnections during repair and testing are much easier now.
2. Invest in a cheap USB microscope or make one yourself from an old webcam.  I could not clearly examine the traces without it.
3.  Apply flux from a syringe before soldering.  I am familiar with rosin core solder but applying flux separately was like night and day.  Soldering 64 pins was greased (literally) lightning!
« Last Edit: July 06, 2016, 10:36:29 PM by apsteinmetz »
-- Art
Amiga 1000 (mothballed)
Amiga 2000 2.04 + GVP 2000-030/4meg + GVP 2000-HD + Starboard 1meg + Microway FlickerFixer.
Amiga 1200 (repaired by ACILL)

Offline Acill

Re: My A2000 restore. Mobo Resocketing fun
« Reply #1 on: July 06, 2016, 09:24:15 PM »
Let me be the first to say WELL DONE!! I knew you could do it as long as you took the time and did it correctly. I am glad to see the A2000 is alive. Get those traces covered up with some solder mask, if you cant find that you can use some conformal coating, or clear nail polish even works. Its very important to get the bare copper covered.

Proud Retired Navy Chief!

A4000T - CSPPC - Mediator
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Offline apsteinmetz

Re: My A2000 restore. Mobo Resocketing fun
« Reply #2 on: July 06, 2016, 10:21:12 PM »
Thanks, Chief! You are an inspiration!  Thanks for the tip about covering the traces.
-- Art
Amiga 1000 (mothballed)
Amiga 2000 2.04 + GVP 2000-030/4meg + GVP 2000-HD + Starboard 1meg + Microway FlickerFixer.
Amiga 1200 (repaired by ACILL)