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View Full Version : LC floppy drive constantly thinks there's a floppy in it



olePigeon
January 1st, 2010, 01:22 PM
I have an original LC. When I connect a floppy drive to the computer, it constantly thinks there's a floppy disk in the floppy drive even when there isn't. It'll keep prompting me to Initialize or Eject; Initialize gives me a read/write error, Eject doesn't do anything.

I tried connected several different Apple floppy drives and using different cables, but it has the same result. I even tried using the other floppy drive port on the left side of the machine, that also resulted in the same behavior.

Anyone have any ideas what might be causing this? :confused:

channelmaniac
January 1st, 2010, 05:56 PM
Sounds like the IWM chip has gone south.

olePigeon
January 2nd, 2010, 11:19 AM
I have a second LC motherboard that doesn't boot that I can use for spare parts. Do you know of a reliable way of determining which chip is the IWM chip? I can probably use the chip from the other motherboard, assuming they're the same part. I tried following the leads but I'm just not certain.

channelmaniac
January 2nd, 2010, 07:33 PM
It's been a long time since I've worked on an LC... Look at the silkscreen writing on the board and see if the chips are labeled with their names.

olePigeon
January 2nd, 2010, 09:06 PM
Well, the large obvious chip next to the floppy port is:

VLSI 344S0061-A / VC2982-0002 Below the chip, on the motherboard it reads: UJ1 SWIM+

I did a Google, and according to Apple's developer tech note for the LC II, "Floppy disk: one internal 20-pin floppy disk connector. One 1.4 MB Apple
SuperDrive with Super Woz Integrated Machine (SWIM) interface is standard." Seems like my best bet, but I wouldn't mind a second opinion (I'm not ugly! :P)

channelmaniac
January 3rd, 2010, 01:59 PM
That's the chip...

olePigeon
January 3rd, 2010, 05:19 PM
I'm out of my league, here. I can't even stick my soldering iron in there without being forced to remove the VRAM and DRAM holders, plus an unfortunately placed capacitor, and the floppy port plug. If I remove all of those, I can finally get to the chip, but it's one where the pins curls in on itself. I can't even use soldering wick on it. At this point, if I'm lucky, I think I'll just buy a 3rd motherboard and hope there's nothing wrong with it. :/

channelmaniac
January 3rd, 2010, 07:20 PM
If you have another motherboard with a good SWIM chip I can swap 'em around. I offer that kind of repair service.

It's a PLCC type chip if memory serves me correctly. (pins curl under)

olePigeon
January 3rd, 2010, 08:39 PM
I appreciate the offer, but the cost of shipping and labor would outweigh the cost of just getting another machine.

Edit: Come to think of it, maybe I will invest in a decent hot air gun. Do you have a suggestion for a brand and/or ballpark price? I found a this (http://cgi.ebay.com/SMT-SMD-Hot-Air-Desolder-Rework-Station-Welder_W0QQitemZ200357778023QQcmdZViewItemQQptZLH_ DefaultDomain_0?hash=item2ea6411267#ht_8122wt_1002 ) on eBay. Seems OK but I have no frame of reference, I've never bought one before.

channelmaniac
January 4th, 2010, 11:43 AM
I don't use hot air, but rather hot iron to remove and replace. Hot air requires solder paste which has a limited shelf life and is a PITA to use.

Using a hot iron with a cut conical tip and some liquid rosin flux is MUCH easier to use.

I have a PACE MBT-250 solder/desoldering station with enough irons to do everything but the real wide TSSOP or chips in BGA packages.

glitch
January 31st, 2010, 06:37 PM
Oh, I hope you haven't removed the SWIM yet! If you haven't yet recapped your LC, that's most likely the problem. I repair old Macs as a hobby/side business, and I've never found a LC, LCII, or LCIII that didn't have leaking electrolytic capacitors. They cause every imaginable problem: wobbly/scrambled display, intermittent boots, the "Falling Bomb" sound through the system speaker, random floppy problems, et c. The surface mount electrolytics Apple used in the machines of the time were of inferior quality, and to add to the problem, a system powered on at full load after many years of sitting on a shelf will stress the caps harder, as they're probably in need of reforming.

You should immediately open your LC and check for corrosion or something that looks like partially evaporated cola, especially in the analog area near the back corner, opposite the power supply. Clean any off immediately: in addition to causing electrical problems, the leaked electrolyte also destroys PC board traces, causing them to erode or detach from the board substrate. Wash the area using isopropyl alcohol and Q-tips. You should then replace the electrolytics with new ones: a lot of people recommend tantalum caps, but I like to use aluminum electrolytics so the rebuilt motherboard looks like the original. You can get the replacements from Mouser for less than $10.

When you remove the old caps, don't try to desolder them: there's a good chance the traces' attachment to the board isn't great from the leaked electrolyte. I use sharp, close edge cutters, and cut the caps off near the board. A quick swipe with the soldering iron removed the bit of the cap pin still on the motherboard. Soldering the new caps is usually easy with a traditional iron, just make sure to use a fine tip.

olePigeon
February 2nd, 2010, 12:42 PM
I ran my motherboard through the dishwasher for a few minutes (no soap, no dry cycle.) Even the rust around the caps was gone, looked new. I'm letting it dry out for a couple days before I give it a try. If it still doesn't work, I'll try replacing the caps. My local surplus store has surface mount caps for 2 of the 3 types on the motherboard for a nickel a piece. They don't have the 3rd one (the really tiny one.)

I didn't think to try and clip off the capacitor. My other motherboard I tried to desolder and tug gently with some pliers, and the contact just came right out. :(

glitch
February 2nd, 2010, 01:37 PM
I had the same experience with the first LCII motherboard I recapped -- many of the pads pulled up, which led me to discover the electrolyte was separating the traces from the board. Since then, I've always cut them off. I've got a peanut can partially full of bad capacitors from Apple computers!

If you can't find the little capacitor -- I'm guessing the 1 uF @ 50 V -- send me a message and I'll send you one. I buy them in whatever quantity gets me a price break, since I recap a fair number of these boards. They're used infrequently, so I've got a pile of them (still haven't used up the 50 I initially bought!).

You can also dry the board using a hairdryer, set for high speed and high heat. Building a tin foil reducer around the mouth of the dryer will accelerate the air, which is more effective at dislodging water droplets from under ICs and sockets. Just don't make the opening of the reducer too small, or you'll overheat the hairdryer. There's a real tool for that job, which is nothing more than a hairdryer that's meant to deal with the increased heat, but it's not worth buying one for just one project.

fred3rd
February 2nd, 2010, 07:08 PM
If you have an extra mb maybe swapping them would cure it.

olePigeon
February 3rd, 2010, 08:43 AM
I'm already using the extra motherboard. :P