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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: Holley on September 18, 2004, 10:03:44 PM
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Good news is today I got an A2000 free, thanks to a very nice chappy who advertised it on Amibench :-)
It's got KS 2, 1Mb ECS, 'HardFrame' SCSI card with 50Mb Quantum harddisk. Also got a Philips Scart monitor, two mice, very nice (yellow, but hardly used) keyboard, a wierd A5 serial scanner, and a pile of disks including a fun Morph program.
(before you ask it's just a nice old A2000, not a mint boxed prestige flagship model with military grade CPU :-D)
Anyway, the bad news is that while trying to coax the 2nd floppy into action I caught a fraid power lead on the PSU case :-( A small spark ensued, and while it carried on working fine for the moment it didn't reboot (and hasn't since).
The power is perfect on 5 and 12 volts, and the ground is good. The harddisk powers up fine and the floppy light comes on when I pop a disk in, also the video recieves a blank signal.
So, any suggestions as to what I've cooked? I have a rough but working A500+ that I can raided for spare chips if need be ... help!
(I was just looking forward to bunging in a 1Gb harddisk and CDRom, and getting stuck in :-()
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Let me understand this, you were working on it when it was on??? How did you short it out again?
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The 2nd floppy power plug was hanging on one ground wire without the plastic clip on the back, the other 3 wires were close to it, I'd just moved the ok power connector from one drive to t'other and tried moving the floppy cable a couple of times (it looks like the cable is duff and only works on the first un-twisted connector, and the 2nd floppy drive is broken as well).
Obviously none of this with the power on!
Anyway, I was trying different combinations and powering on in-between, on the last time I did it the broken power connector was flopped near the PSU and one wire touched it.
When I first openned the case I saw the wires and thought 'must get that insulated soon' ... d'oh! - should know better :-?
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The power is perfect on 5 and 12 volts, and the ground is good. The harddisk powers up fine and the floppy light comes on when I pop a disk in, also the video recieves a blank signal.
What color/colors do you get on the screen ? These colors can tell you if there is a problem. I would first check all the voltages at the motherboard connector. There are files on Aminet that tell you what the bootup colors mean, and also what the voltages should be on the motherboard connector.
Ed King
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You could have damaged a CIA chip, Paula or Gary, and as luck would have it they`re socketed so you can swap the ones from your A500 to test them.
Other than that, there`s a load of 74xxx logic between Gary and the floppy connectors that could have taken a hit.
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Ed - Nothing comes up, it's just a black (or very dark grey) signal.
Doobrey - Time for some trial and error then ... I'll get busy tommorow, starting with the CIA!
I've never been any good at remembering which bits of the chipset were connected to each other, so thanks for the tips :-)
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The power supply into the motherboard has a number of seperate inputs, including a seperate +5V and +5V_user.
It would be worth checking all voltages on the connector CN400. Details on the schematic, which you can find here:
http://amiga.serveftp.net/schematics.html
I can't remember if the A2000 had fuses on the motherboard or not, but chances are one of these might be open circuit?
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That site also has the pinouts here (http://amiga.serveftp.net/HardwareBook/connector/power/amiga2000power.html).
I've checked 'em, they're all fine, even the tick :-) +/- 5v is at 5.15 (including the 5v user) and +/- 12v is at 11.95. There's no fuses on the motherboard.
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Yay progress :-)
Replaced the CIAs & Paula (no change), then Gary, and it now boots from the harddisk or to the regular purple / floppy screen if the SCSI card is removed.
Neither floppy works though :-( But I'm tired and it's time for bed ...
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Well, had it working fine with an external floppy (no spare working internal one), but with it's guts all over the place. Bolted it back together and now it only boots to white with no harddisk activity.
Aaargh!
Ho hum, time for more trial and error ... later ...
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Sounds like a lot of effort in trying to revive it. I don't think id worry to fix it, but to maybe use it for parts for another Amiga 2000. If you want to be a true amigan, then keep working on it till it works! :-) :-D
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Not really a case of wanting to be an Amigan, just not wanting to waste a fixable Amiga - there's enough of these in landfill already!
Looks like Paula is no longer getting power, according to the Aminet A500/2000 troubleshooting FAQ this probably means a 1 Ohm resistor labelled R200 is burnt out. Time to order some stuff from RS (might as well get some clock batteries while I'm at it!).