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Apple IIGS Rom 01 Repair


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Took a punt on a "untested" Apple IIGS machine off ebay a few weeks back and of course it was dead. I've always wanted to play around with vintage Apple II's which I remember we had at primary school. I have no interest in Mac's.

I really don't like how they name the boards based on the rom revision. Rom 00 and 01 are pretty much the same with 256k built in with a 1 meg rom. Rom 03 is a decent upgrade with 1 Meg on board and has 2 x 1 meg rom slots and is suppose to be 10% faster.

I missed out on the Apple RGB monitor so I made a IIGS to Commodore 1804s cable which works nice.

 

Symptom: Dead

Fix: The GS uses a 65C816 which is a 16/8 bit hybrid of the 6502, kind of like the 8088 used in early IBM's and Clones.

First I checked both the reset and clock which were fine, looking at the Data lines 2 were completely dead.

Sadly I had no spare CPU's but so I ordered several from China which still haven't arrived. Luckily The French fellow I bought a Rom 03 board from threw one in for me and it arrived last week. Replacing the CPU the machine sprang to life.

 

Do some reading about the machine it has a built in diagnostics which is nice. To access the diagnostics you hold down Apple open and Option on power up (I didn't even know what apple open was)

 

IMAG0912.thumb.jpg.3e7e63fe4299bfa2246abfb727e75607.jpg

Running the diagnostics I got this error which in the error list I found on the web means Ram data error as per below.

 

Sound Test:3

AA= 0C

DD= 01: RAM data error

02: RAM address error

03: Data register failed

04: Control register failed

05: Oscillator interrupt timeout

 

IMAG0913.thumb.jpg.b5c4c17de73c7587a2593f3be173c1bc.jpg

Ram used is 4464, I pinched one off a spare Turbo XT Motherboard and tried piggy backing on top.

 

IMAG0916.thumb.jpg.bd9000fc9188f3ff42d4bf795004f2e9.jpg

 

Ran test again and :)

 

More Apple IIGS repair logs to come including my Rom 03 board with battery corrosion damage, 3 disk drives I repaired and a Apple IIc 9" green screen monitor I'm currently working on.

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