Apple II Disk Repair - On The Cheap!

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woogie's picture
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Joined: Dec 20 2003
Posts: 263

(Reprinted from parts of a "II Alive" magazine article)

"I own an Apple IIe with two Apple Disk II drives. One day
recently I found it necessary to remove and re-install the
drives. Shortly after hooking everything back up, I attemp-
ted to save a file to the second drive. At once, the power
supply burped, the computer crashed, and the drive started
to smoke!

I hit the OFF switch in a flash. I looked inside my comput-
er and noticed that I did not properly hook the drive to the
20-pin connector on the controller card. I pulled all the
cards and did a system diagnostic. System OK. I put the
Apple II disk Controller card back in (after disconnecting
Drive 2) and powered up again. My first drive booted normal-
ly, but had developed an inability to write.

I called the service dept. of my local Apple Dealer and ex-
plained the problem. They told me that I need an analog
board for each drive, which would cost me about $89 each.
(OUCH) Sun Remarketing's price for the card was about the
same with a trade-in.

I decided to try and fix the drives myself. I removed the
four screws on the bottom of Drive 2 and slid the cover off,
wincing at the smell of cooked silicon, and noticed that one
74LS125 was cracked. Several others looked damaged as well.
The circuit traces and wiring looked fine in both drives.
I decided to investigate the availability of these chips
and just replace them, if possible.

My trip to Radio Shack was disappointing-their prices for
chips were more than I anticipated. Remembering my JDR
Microdevices Component catalog, I was pleased to find all
four chips listed. JDR's prices are as follows....

74LS125....Quad-3-State Buffer.............$ .39
MC3470.....Floppy Disk Read Amp............$1.39
CA3146.....Hi-Voltage Transistor Array.....$1.19
ULN2003....Darlington Transistor Array.....$ .69

At those prices, I ordered the chips and a few spares for
both drives. When I received the chips, I carefully pulled
each chip, taking careful note of each chip's orientation,
and installed the new ones. With great care, I reassembled
the drives, connected them to the interface card (being
careful to hook everything up properly this time) and held
my breath as I thumbed the power switch.

I booted the drives and put them through a series of tests.
To my great relief, they are fully functional again. They
work like new and my total cost was under $20. I was lucky
that these were older drives and the chips were not soldered
in as they are in the newer drives. (Even so, someone who is
handy with a desoldering tool could save even thoses.)"

............................................................

I thought this would be a helpful article for those who are
trying to save/preserve their older Apple II series computer
hardware. I have a few of these tech articles floating a-
round here that I saved from "back in the day".

This magazine is no longer in print. I do believe that some
back issues are available on some of the Apple buy/sell
threads and sites. The magazine had many useful articles on
hardware maintanence and software programming. It's a shame
that it has disappeared.

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Pease's picture
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Joined: Feb 11 2004
Posts: 30
Tech Info File

Thanks for the article. I'm putting this into my Tech Info file in case I need to repair my Apple II stuff. I have an Apple IIc and a
Apple ][e. Are you going to reprint any other tech articles? I think this would be a great thing for those who are working on the older computers because nobody supports them anymore except small user groups and this forum.

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I love old Apples!