Accessing CIA chips in Amiga 3000 and 2500?

[HolySamosa]

First post here.  :-)  I'll try to follow up with a proper introduction in the Introductions forum.

Any suggestions on how to access the CIA chips in an Amiga 3000 without completely disassembling the the machine?

While I'm at it, also on the 2500?  I'm thinking perhaps I can access them after removing the power supply...

Thanks!
Jeremy

[Oldsmobile_Mike]

Welcome! Two totally different beasts. In the 2500, remove the cover, the drive sled (with PSU), done. In the 3000, make sure you have some finger bandages ready, and good luck.

Why do you need to access the CIA chips?

[HolySamosa]

Thanks for the reply, Mike!

I do have Band-Aids handy. :-)

As for why I'm trying to get to the CIAs, I have collected an A1000, A2500 and an A3000.  All of which malfunction in some manner, a couple of which may be due to CIA issues.  I was hoping that a little chip swapping between the three might help me diagnose the issues and perhaps get at least one up and running:

• The A1000 gives a dark gray screen at power on.  Doesn't get to Kickstart. Reading online suggests this could be a CIA issue.  I did try swapping the positions of the CIAs in this box with no change.
• The A3000 generally works, however it will lock up fairly often when trying to access the disk-- either floppy of hard drive.  Readings suggest this is a CIA issue.
• The A2500 hasn't been well cared for.  Can't immediately recall if it makes it to Kickstart, but it throws Guru Meditations.  Don't recall the order, but I did make note of these: #00000008.00202FDEm #00000004.00000000, #00000004.00202FDE, #0000000B.00001970.

Think I'm on the right track with the CIA swapping?

I lusted for an Amiga as a kid in the 80s and never could get one.  Better late than never, eh?  Now I just have to get 'em running!

Thanks!

[Oldsmobile_Mike]

Definitely! Better late than never. If you haven't already, I'd check those batteries in the 2500 and 3000 ASAP!  Also try reseating all the socketed chips, cleaning off any corrosion, etc.

[HolySamosa]

Haven't got a visual on the 2500 battery yet.  The 3000 battery is leaking and there is a small amount of corrosion in the surrounding area.  Doesn't look too bad.

[kjmann]

Get Those batteries out of them quick! The original barrel batteries are notorious for leaking and damaging motherboards. Whether they are leaking or not you should get them out quick before any damage (Or More Damage) is done. The Systems will run just fine without them installed, but the clock will reset every time you power down (No big deal there).

[motrucker]

I am not sure these are CIA problems. They could be, but these are not usual. The most usual is your mouse and/or joystick not working.
IIRC aren't the A3000 chips surface mount? The 2500 are easy to get at.
Have you tried running SnoopDOS? That can tell you exactly where the problem is. Very handy program!
Also, do make sure you get those batteries out of those machines, if there is ANY sign of leakage! Specially the A3000. A bad battery can easily kill the Mobo in an A3000.

[Oldsmobile_Mike]

Had to pull up a pic because I couldn't remember either. Appears the A3000 CIA's are socketed, all the way in the back, below the PSU and drive sled & whatnot. Swap them with the ones in the other systems, if the problem changes then you know you've found your culprit.

Pic:

http://www.bigbookofamigahardware.com/bboah/media/download_photos/a3000rev61mb_1_big.jpg

But batteries first!

[mechy]

Thanks for the reply, Mike!

I do have Band-Aids handy. :-)

As for why I'm trying to get to the CIAs, I have collected an A1000, A2500 and an A3000.  All of which malfunction in some manner, a couple of which may be due to CIA issues.  I was hoping that a little chip swapping between the three might help me diagnose the issues and perhaps get at least one up and running:

• The A1000 gives a dark gray screen at power on.  Doesn't get to Kickstart. Reading online suggests this could be a CIA issue.  I did try swapping the positions of the CIAs in this box with no change.
• The A3000 generally works, however it will lock up fairly often when trying to access the disk-- either floppy of hard drive.  Readings suggest this is a CIA issue.
• The A2500 hasn't been well cared for.  Can't immediately recall if it makes it to Kickstart, but it throws Guru Meditations.  Don't recall the order, but I did make note of these: #00000008.00202FDEm #00000004.00000000, #00000004.00202FDE, #0000000B.00001970.

Think I'm on the right track with the CIA swapping?

I lusted for an Amiga as a kid in the 80s and never could get one.  Better late than never, eh?  Now I just have to get 'em running!

Thanks!

on all of them, check and reseat all chips. Check power supply on the A1000 for proper voltages.
on the 3000 its likely a software issue, also could be a scsi termination issue. Even battery leakage that doesnt "look bad" can be bad. alkaline from the battery can seep into the inner layers thru solder joints and cause damage. I suggest removing the battery now! nuetralize the area with a acid(lemon juice,etc, clean it off with iso alcohol and dry it well.
The A2000 is hard to guess, reseat chips,check for battery corrosion near the roms and 68000,its a common problem. replace sockets that have corrosion in them if you want a stable machine. once the plating is gone on pins its not likely it will run stable over time. pull all cards/hard drive and see if it will boot to a good workbench disk.

i doubt any of the problems above had anything to do with cia's ...

[HolySamosa]

Thanks again for the advice.  Hopefully I'll get a chance next week to pull the motherboards from the A3000 and A2500 and unsolder the batteries and perform some other checks.  

I now have the A1000 powered back up and have a better description of it's behavior-- I'll start a new thread to keep things strait.

Thanks!