Re: MFM drive gone nuts

From: Michał Pleban <>
Date: Sun, 20 Jul 2014 12:57:17 +0200
Message-ID: <>

> That's a Miniscribe 3650, I presume. (Or it's RLL brother, 3675)
> I sold many of them back in the 80's, and I'm quite familiar with
> them. It's been left in burn-in test mode.

The sticker in the front says it is a MiniScribe 3425, according to the
information on the Internet it's a 20 MB model.

> I THINK the first three jumpers have to be in place for normal
> operation - if one's nicked, it goes into one of several test modes.
> One is a "fanout" seek test, the other a random, another a sequential
> step test. it's been a VERY long time between drinks.
> Have a play with the first 3 jumper positions (the ones on the edge
> over the narrow edge connector).

Ah, I found them! They were well hidden under the platter and hardly
accessible. They are DIP switches, not jumpers, and changing the second
jumper disabled the seek test.

However, the drive is still not recognized by the controller - still all
operations result in a timeout. I played with switches 1-4 but none of
the configurations worked. However, the drive access LED is ON when the
computer tries to read from the drive, for what it's worth.

> But all is not lost - I could go through the whole process of checking
> the drive but this guide from Miniscibe is pretty comprehensive and
> though may not be specific to your drive model, it will be pretty close.
> **

Thank you, I have browsed through it. Unfortunately, all the procedures
described in it are for DOS so they are no help in reading the drive
from C900. As a last resort, I will try to dump the drive from a PC
side, but I am reluctant as to reformatting it because that would mean
destroying all Coherent data that may reside on it.

> On PC controllers, they should always be jumpered as DS1, and the cable
> twist makes the drive on the end (which should be terminated) drive 0.
> (only ONE DS jumper should be enabled at any one time.

That got me thinking. The drive is jumpered as the drive 0, but the
cable is NOT twisted. Does it mean that the drive should be jumpered as
drive 1?

The cables are terminated properly on the drive from what I can see.


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Received on 2014-07-20 11:00:02

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