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IBM PS/1 2168 restoration: Floppy drive replacement struggle

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First post, by fabiensanglard

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Hello all,

I am currently restoring an IBM PS/1 2168 (Mini-Tower). The floppy drive no longer detects disk eject so I am trying to replace it. I ordered a new one on ebay and it is not working. The light of the drive is always on. If I insert a disk, it continuously try to read. Note that the BIOS recognize it and there was no boot errors.

I wonder if the model I got is deficient or if I am the problem by not doing it right 😜 !

The original drive seems to be using a "regular" connection. See the photos:

The attachment original_top.jpg is no longer available
The attachment original_back.jpg is no longer available
The attachment cable.jpg is no longer available

The groove "guide" is on the back.

Here are the new drive photos

The attachment sony.jpg is no longer available
The attachment sony_back.jpg is no longer available

Any advice or suggestion would be appreciated 😀 !

EDIT: Now that I have looked at the photos side by side on this post, I noticed that the groove on the connectors are different. The original drive has it on the bottom while the Sony drive has it on the top. It is likely to be the problem (I have vague memories of the red side of the cable having to be facing the power connector).

Is there a name for this polarity? What type of drive or adapter should I use?

Reply 1 of 7, by analog_programmer

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Pull the plastic with grove from the connector and reinsert it reversed position, then reconnect the cable in reversed position.

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Reply 2 of 7, by fabiensanglard

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The plastic with grove (I assume you mean on the Sony floppy disk) is not coming out. I tried to pull on it pretty hard and it is not moving.

Reply 3 of 7, by DaveDDS

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On a floppy interface cable, typically every second pin is ground, this give
nice signal/noise protection as each real signal wire is separated from the ones
on each side by a grounded wire.

The way ribbon cables are made, this means that all the pins on one side are
ground.

Drive select is active low, so the light staying in usually means drive select
is stuck low - which happens if the cable is reversed.

On the cable, the end with the red wire which is the one closer to the twist
is the pin 1-2 end.

On the drive, there are typically TWO physical means of insuring the cable is
oriented correctly:

Note the missing pin at the lower-left... many (but not all) cables have
this pin "blocked" so that it cannot be inserted at the other end (where the
matching pin is present).

The "slot" 1/2way down the side of the housing prevents a matching "bump" on
the cable from being inserted the wrong way (actually it's the non-presence
of the slot on one side that prevents it) - unfortunately many cables don't
have the "bump" and can be inserted either way!

I also see on your SONY drive a /\ marker indicating where Pin1 should
go.

So it looks to me that with the drives in the position shown, the red wire
should be to the left, and the "bump" on the bottom...

(Note - depending on the mainboard connector, it may also be possible for the
cable to be reversed there)

Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal

Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal

Reply 4 of 7, by fabiensanglard

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the "bump" on the bottom...

Agreed but the drive will only allow the cable to go in "up" because the groove is "up".

Reply 5 of 7, by maxtherabbit

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The easiest fix here would be to just use a cable without the key

Reply 6 of 7, by DaveDDS

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fabiensanglard wrote on 2025-01-19, 01:19:

Agreed but the drive will only allow the cable to go in "up" because the groove is "up".

Based on the location of the missing pin, and the "slot" in the board, it looks to me like someone
has managed to pull the shroud off the pins and stuff it back upside down.

If you are able to do the same, that would be best, otherwise find a cable without the "bump" or
grind/cut it off the one you have... good luck.

Dave

Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal

Reply 7 of 7, by DaveDDS

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Also, looks like there's a metal plate on the bottom of that drive?

You might be able to remove the plate to expose the bottom and cut away where the "slot" should be
(fine wire cutters and/or a dremel .. just don't damage the pins)

Dave

Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal

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