Re: Troubleshooting the disk drives in a 8296D

From: Nicolas Welte (
Date: 2004-12-06 10:34:57

Hallo Marko,

Marko Mäkelä wrote:
> a 901885-04, an EPROM labeled 251474-01B, and a 74LS04.  According to
> information composed by Mr. Levak, the 901885-04 is 6530-47 for Micropolis
> drives.  The drives are from Matsushita, Japan.

My drive uses the same EPROM, but a different 6530. Anyway, any 6530 from a 
dual drive can be used, because the ROM is replaced by the EPROM.

> What about the write protect sensors?  I figured out that the wires are
> red, white and a twisted pair of orange and black, connected to the 24-pin
> connectors on the analog board as follows: pin 1=red, pin 2=empty,
> pin 3=orange, pin 4=black, pin 5=white.  I also noticed that the drives have
> index hole sensors, but I forgot the colors.

They even have track 0 sensors, but they're not used.

It seems the WP sensors aren't connected to an IO chip at all, but to UD9 
which then inactivates the WE signal directly. (If I hadn't said so already, 
my copy of the 8250LP schematics isn't very readable).

> Do you have a 251121 rev. B analog board?  If you look at it so that the
> power connector is at top left and the R/W head connectors are at the top
> right, then which R/W head connector is for drive 0 and which is for drive 1?
> I have tried swapping them without success.  I'd like to make sure that they
> are connected properly before trying something else.  The two 24-pin connectors
> are easier to get right, because the drive LEDs are connected to them.

drive 1 (left, viewed from front) is connected to P1 (right as viewed by you)
drive 0 (right) is connected to P2 (left)

The 24 pin connectors are P4 for drive 0 and P5 for drive 1. On pin 1, there 
is a red cable, and pins 2,23 and 24 are empty.

The other connector, P3, which goes to the logic board, is connected somewhat 
weird, because it wasn't meant to be used with a ribbon cable, but with a 
direct plug. It's this way in the 8250LP, where the analog board sits between 
the two drives, under the logic board. So the ribbon cable is split into two 
and there are two single row connectors at the analog board. Just make sure 
the red cable goes to pin 1 on both ends.


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