Missing Pressure Pad (and Shield) from 400K Floppy Drive

[RedJacketPress]

I've been servicing the 400K drive from my Macintosh 512K -- the drive spins and ejects (and the load and eject mechanism feels great), but it won't read any disks -- it spins up and ejects a disk almost immediately. I think I might have found the reason why -- the felt Pressure Pad is missing, and I suspect the heads aren't making good contact with the disk surface. (I did a bit of disassembly hoping I might find it in the drive, but no luck there.)

(The Shield is missing, as well, though perhaps that was a change made during manufacturing? This drive is from 1985.)

I haven't been able to find a source for replacement. I'm fairly confident I could 3D print a useful piece, though I'm not sure what material to use for the felt pad that wouldn't inadvertently damage the disc surface. (Though come to think of it, a 400K drive would only read one side of the disk, so perhaps that doesn't matter as much?)

Any suggestions of where to find a replacement or where to find the design for a replacement or what to use as a replacement?

Thanks!

 

[bibilit]

This part is often missing, if the drive is stuck and carrier in the upper position, trying to insert or remove a disk will push the felt out of position.
IIRC you can use a similar part from an Apple II drive… or find a faulty drive (not easy i know)

 

[pfuentes69]

This topic interests me...
I want to replace mine because is in bad shape and I was thinking that maybe I can use the tool to make holes in the leather belts and make a new felt pad... Or maybe with some patiente cut one with scissors.
I was planning to cut it from one of these adhesive felt pads that are used to put in the chair legs...

 

[mg.man]

Unconventional, I know... but I've done this with a Q-Tip on a few drives...

As they say... desperate times...

Besides, for a 400k disk the upper surface doesn't really matter. I'd just advise caution and avoid inserting a valuable 800k disk!

 

[cheesestraws]

Yeah, I too had some success with the top of a cotton bud

 

[mg.man]

I too had some success with the top of a cotton bud

I promise I won't do the above to the 400k drive I owe you!! I really need to get that sorted!!

 

[pfuentes69]

Unconventional, I know... but I've done this with a Q-Tip on a few drives...
View attachment 43234 View attachment 43235
As they say... desperate times...

Besides, for a 400k disk the upper surface doesn't really matter. I'd just advise caution and avoid inserting a valuable 800k disk!

Great!
It's equally ugly than brilliant!

 

[mg.man]

It's equally ugly than brilliant!

...and easily / cheaply replaced whenever you feel the need!!

 

[mg.man]

FYI, I usually use a scalpel or brand new utility knife blade to carefully trim away the lower cotton... otherwise there's too much there and the 'tip' sits pretty high. Also... the paper-stem ones seem to be a perfect fit! Aren't the plastic stem ones illegal in the EU now anyway?

 

[RedJacketPress]

I'm confident enough in the health of the Mac to order (and assemble) a Rominator, so I'll probably just boot from the ROM as a matter of course. But I would like to have a working Floppy Drive.

How does the Q-Tip stay in place? Is it a tight fit?

 

[pfuentes69]

Aren't the plastic stem ones illegal in the EU now anyway?

Yep, now these must be paper-based...

 

[cheesestraws]

I promise I won't do the above to the 400k drive I owe you!! I really need to get that sorted!!

In case the ghost comes out of the haunted one to get you? :-D

(sorry, I shall stop derailing this thread now)

 

[mg.man]

How does the Q-Tip stay in place? Is it a tight fit?

It is... certainly the genuine J&J "Q-Tip" (Cotton Buds here in the UK) ones are a nice snug fit.

 

[CC_333]

the paper-stem ones seem to be a perfect fit! Aren't the plastic stem ones illegal in the EU now anyway?

Yep, now these must be paper-based...

I don't care much for the plastic-stemmed ones anyway, so I'm not super sad to see them go. I find them too thin and bendy to work with.

The paper-stemmed ones are much better.

c

 

[WillJac]

I not sticky felt feet and cut out very small round pieces but had to double it in to knees and stick it on. It works. One piece was not enough pressure why I had to double it.

 

[RedJacketPress]

The Q-Tip-as-Pressure-Pad solution worked well, and was relatively easy to implement. I got the Mac 512K to boot from the a System disk, though it got only as far as a blank desktop before it encountered System Error 15 -- I'm thinking this is probably a further issue with the 400K drive, perhaps a failure to access a particular part of the disk? (I did clean the heads, but I don't know that I have the time or the patience to work on alignment issues.)

In any event, I have a Rominator on the way, so I'll know soon enough if this is a problem outside of the drive!

 

[WillJac]

You can also try recap the floppy. JDW has a good video on this and mouser carts to get the caps. I did all my 400K drives. I have not done the 800 or higher once yet.

 

[RedJacketPress]

That's also an option. I think when I get the Rominator sorted out and installed, I'll connect the drive outside the case and try to get a sense of what it is or isn't happening.

 

[LaPorta]

I never even knew they made any with plastic tubes...

 

[Juror22]

I wish that someone had seen my post and had mentioned the Q-tip idea, when I asked about this a few months back. I went out and spent WAY too much to get one of these pads.

I'll connect the drive outside the case and try to get a sense of what it is or isn't happening.

That's how I tested the last one 400K drive I bought. (I hooked it up to my external case's cable)