Philips NMS 8245 FDD keeps busy, disk offline

Supporter (4)

26-01-2021, 06:42

Hello guys,

For a year or so I've been the proud owner of a Philips NMS 8245, which unfortunately had a busted FDD. It's been sitting on the shelf for a while but I've been attempting to get the drive fixed in my spare time. A little background information below..

The MSX was put away around the 1990s with a Floppy inside, which I could only remove opening the FDD and removing it manually. There I also noticed a busted belt, where I got a replacement for from Bas. However, after fitting the new belt the MSX would still report disk offline and I could not hear the drive moving at all when attempting to read. I figured something else must've been broken and set it aside and searched for a new drive.

So I purchased a drive somewhere online (the Dutch Marktplaats), a Chinon FZ-354, which was specifically targeted at Amiga or MSX systems (being a true double density drive). It came with the regular 34 pin PC connector however, for which I got the Omega FDD adapter. Just yesterday I soldered the connectors onto the tiny PCB. I didn't solder the "RDY" contact (perhaps I should've?) and attempted to connect it to my MSX computer.

The good news is the new drive is actually spinning, so that's a minor win. :) The downside is it never stops spinning and the MSX still reports disk offline.

I immediately thought of the jumpers on the back of the FDD, here is an image of the back of the drive:

It has the following jumpers (for which I believe they mean the following after some web searching):
- DS0: Set as 1st drive (A)
- DS1: Set as 2nd drive (B)
- DS2: Set as 3rd drive
- DS3: Set as 4th drive
- MM: Motor on from motor on
- MD: Motor on from drive select
- DC: Disk change
- RDY: Ready
- TTL/C-MOS: ??

By default the jumpers were set to:
- DS0
- MM
- RDY
-TTL/C-MOS

Just like in the picture. I've tried without TTL/C-MOS and set it to MD rather than MM but that doesn't change the way the drive is always busy.

Any clues on what to check next or where I may have messed up? The MSX has no other mods.

If desired I can take some pictures of the end result tonight so you can see what the current situation looks like.

By Alexey

Guardian (2990)

26-01-2021, 12:42

If you set the RDY jumper, then you need to connect the RDY signal from the motherboard to the drive (solder a wire).

By Manuel

Ascended (17513)

26-01-2021, 13:26

So, try without the RDY jumper.

By AJSchat

Supporter (4)

26-01-2021, 19:15

Thank you for the replies. That was indeed the issue, well, partly. I stumbled upon this MSX FAQ which also mentioned the following:

Quote:

Drive doesn't work and LED of it keeps lit: you put the connector on the drive upside down. Reverse the connector and try again.

Flipping the PCB upside down and removing the RDY jumper fixes the issue, I was able to do a directory listing of an old floppy. Great!

This brings a new issue though, do any of you happen to know of any inverter I might be able to use in this case? I'd hate to buy another FDD and I'd like to keep the original cable intact if it is at all possible.

I've thought about using a regular floppy cable between this and the PCB but that would keep it just dangling somewhere in the case (worst case scenario), there must be a better solution.