Topic: Amiga 1200 Repair Log  (Read 3998 times)

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Offline Womble

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Amiga 1200 Repair Log
« on: August 08, 2014, 11:59:48 AM »
A bit of a break from Arcadia but much the same kind of work involved...

My regular search for interesting faulty stuff on eBay threw up a gem last week, a faulty Amiga 1200 unit.

WTF? - a 130MB 3.5" HDD bodged inside instead of the correct 2.5" HDD on an official caddy? It was held in place by two strips of bent metal and was resting on the motherboard on a bit of roughly cut plastic sheeting. The PC style molex connector power leads were bodged onto the inside of the power connector. All in all pretty nasty.

So, to get a baseline test it was stripped back to a bare bones A1200 to rule out hard drive faults and accelerator card issues.

Sadly it was still dead, no signs of life on the screen, even the noise from the HDD when it was still installed was just the standard HDD spin up and head noises, no signs it was being used by the system.

So I checked the voltage levels first then went back to the board inspection and quickly found the prime candidate for the fault.

Pin 13, i.e. the third pin in from the left is missing all the solder, this is what happens if you touch up old solder joints without using flux, the solder gets sticky and clingy and you end up dragging it away from the joint on the iron. Pin 12 isn't much better but it is still attached, pin 13 is just resting on the pad, which may work for a while until oxide built up at the touch point.

As soon as I applied the slightest pressure to this pin the system booted to the "insert disk" screen.

So the joint and all others on the two messy 74LS245 chips were tidied up to complete the fix.

With the hard drive reattached it booted into workbench happily.

Heres the official caddy and drive from a 1200 and the one they had crammed in.

Both my 2.5" HDD and the 3.5HDD are pretty loud, the current draw from the 3.5" drive causes some image instability when it is accessing data, which is a design flaw on the board that I could rectify, but with a CF card the current draw will be minimal so the problem will likely vanish anyway.

Anyway - a quick reassemble and time for a full test...

...with the title of choice for all my 8 and 16 bit repairs when possible...

...Treasure Island Dizzy!!

All in all a damn fine eBay score!!
« Last Edit: February 16, 2017, 08:09:58 PM by Womble »
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Offline AndyRCM

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Re: Amiga 1200 Repair Log
« Reply #1 on: August 12, 2014, 05:17:38 PM »
Excellent . . . nice work mate. Good to see a repair done correctly. :)

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Offline Panther

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Re: Amiga 1200 Repair Log
« Reply #2 on: August 17, 2014, 02:42:08 PM »
Lucky find with that accelerator !!