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IBM PS/2 35sx floppy strange error 604

sumariane

New Member
Joined
May 12, 2022
Messages
9
Hi everybody, I just bought an ibm ps/2 35sx. Unfortunately it’s floppy doesn’t work and I’m aware of the fact it could be its old capacitors.
So I decided temporarily to get a standard floppy adapted following some examples on internet, so that I could at least use the starter disk. Only problem is that whatever drive I use, even an old ps/1 floppy, it throws error 604 at boot. I’ve already modded the Dallas etc chip. With its original drive this doesn’t happen, it’s very weird.
i forgot to say that this error comes after 162 and before 163, which are normal because I’m not able to configure the pc. I tried to find documentation about this error but it only says “non-media sense error”.
Has anyone any idea?
 

whaka

Experienced Member
Joined
Feb 26, 2021
Messages
62
Location
France
hello,
mean the diskette type can't be detected. can't sense if DD or HD, ED if 2,88 drive
i don't really understand why you get it, as standard drive usually are media sense, but maybe not very recent drives ? or something in the wirering ?
it's not critical, you can perfecly use it. but if for any reason you decide to format a 720k floppy, you'll need to specify it, otherwise it'll be treated as HD floppy.

edit : and i confirm for capacitors on the original drive, specially true if it's an ALPS branded.
depending how corrosion had worked... you may have more or less work to do.
spindle motor is working ?

edit bis, to be a bit more precise on 604 error.
it's an ibm weird thing. some ps/2's don't required media sense capable drives, but at some point in ps/2 life, they decided to add it...
some ps/2's don't require it, some as the 35 need it, or it spit on you 604...
so, even with some ps/2's or ps/1 drives, you can get it. check if drives you use have the switch to detect floppy type.
 
Last edited:

sumariane

New Member
Joined
May 12, 2022
Messages
9
Hi, thanks for the reply. Ok probably using a standard more modern floppy drive I have to give the ibm some sort of signal that I’ve inserted a 1.44 floppy. Unfortunately It is critical because even if I press f1 and it boots on the hard drive, I can’t use the floppy, it gives me a generic reading error.
tried the original which is a Mitsubishi Mff355c-mq1 with two smd capacitors near the motor which might need replacing. The motor goes slightly up and down a bit with an excursion of about 5mm and then it stops But it doesn’t give me the 604 error.
 

whaka

Experienced Member
Joined
Feb 26, 2021
Messages
62
Location
France
604 shouldn't be a probem past F1. i never had issue with that.
except you need to specify to format command what kind of format you need, or it treat DD as HD floppy, that's all.
so there's probabely another problem elsewhere.

maybe it can be due to the flat dallas. i know PS/1 2011 is unable to use his floppy drive (except for dir command...) with a dead battery.
once you get a good battery, all come back to normal. i can't tell is the 35sx act the same, but maybe...

are you sure you didn't drill too far in the dallas ?
i got a 55sx where the first owner did the mod, but he drilled too far... and killed the chip itself, giving strange problem as random reboot/freeze.
 
Last edited:

sumariane

New Member
Joined
May 12, 2022
Messages
9
Yes and you’re right about the floppy not working in the ps/1 , the catch 22 is that in the ps/2 you can only run the setup from a special starter floppy, that’s why I’m stuck. What I might do is swap the ps/2 Dallas with the ps/1 one and see if that changes anything.
The thing is I thought the mod was ok because the errors 161 changed in 162 so I assumed everything was fine with that chip. And still doesn’t explain why with the original drive I don’t get this error 604. These machines are a mistery …
 

whaka

Experienced Member
Joined
Feb 26, 2021
Messages
62
Location
France
you don't get the 604 with original drive, because he have the switch and circuitry to sense if floppies are DD or HD.
so if you're sure of your dallas mod, check if the drives you used have the switch (the PS/1 drive don't, for sure)
 

sumariane

New Member
Joined
May 12, 2022
Messages
9
Ok so I’ve tried swapping the Dallas chips and didn’t change much except an error while doing The memory count. Your answer would explain why I get this error, I assumed that ps/1 floppy drive was quite similar to the ps/2 ( the model I own it’s only a year older than the ps/1 2011) but obviously it isn’t and also the newer model I’m trying. What I did with the new 2000’s drive was getting rid of 5 and 12 volts and grounding the pin 4 as explained in other videos and websites and powering the drive with an external cable but no luck with that, it’s like my ps/2 is different from those other models.
 

whaka

Experienced Member
Joined
Feb 26, 2021
Messages
62
Location
France
to get rid of the error, you need to be sure the drive you actually use have the switch for sensing HD/DD.
then, maybe check the pinout, maybe there's another wire to jump or something like that for media sensing to work.

here are the various ps/2's motherboard floppy pinout : https://ardent-tool.com/floppy/Pinouts.html#40p_Edge
i actually have a 35sx too, but don't remember which connector is used, i belive it's a 40 pins, but only 34 are wirered.

but anyway, as i said, 604 error won't block you for using the drive.
i used non media sense ps/2 drives in my 35 without issues, except 604, of course :D
 

sumariane

New Member
Joined
May 12, 2022
Messages
9
Hi, the other drives don’t have any switch, I think the cable adapter I made is not wiring some pins like you said. I assumed I just had to ground pin 4 and divert the power but then I saw some videos where they connect some even pins to the +5 v, through some resistors so that might be causing that error.

the ardent tool website is really good, I looked at it but unfortunately it doesn’t specify what wiring is needed for very ps/2 models, which apparently varies a lot.

the fact that you’re able to use floppies even though you get error 604 makes me think that maybe there’s something else wrong with my ps/2, maybe the controller.
And that would be it. What kind of adapter are you using?maybe you could send me the schematics so that I copy it.

anyway thanks for your help I’ll make more attempts and if I manage to solve I’ll post it also to help other users that have got the same issues.
 

NeXT

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Joined
Oct 22, 2008
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6,733
Location
Kamloops, BC, Canada
The more I think about this, the more I'm reminded about the issue I had in my Model 80 when I later got it working.
The drive seemed to operate fine but even after a recap it still would not detect a floppy in the drive. The alter high density drives have physical contact switches for both detecting id there is a disk in the drive and for detecting the media density hole. These tiny little switches I've found with time crud up a bit and don't make contact when they should close. They aren't too hard to open and spray in contact cleaner, just delicate.
 

sumariane

New Member
Joined
May 12, 2022
Messages
9
Thanks for the info, I wonder if these switches are also found in my original mitsubishi drive. I think first thing I'm going to try a recap because adapting a modern floppy sounds like a dead end.
 
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