I picked up this Commodore 1541ii drive this past week When I unpacked it, I was surprised by this little slot with a slide switch in the bottom front here. After opening it I found more oddities.

So this thing is a very interesting 1541ii. After seeing the EPROM I figured the wires from it were to switch between some alternate firmware and the factory firmware. It seems originally the wires likely ran out the vent holes in the side and the switch was taped to the side with clear tape. I guess it was removed at some point or fell off. When I turned over the Floppy drive itself, the JiffyDOS label had wedged into it so that sorted that question.

The interesting switch in the front appears to be wired as a 4 position Device selection. I haven’t seen such a mod, but it makes sense. This would make for easy device id changes without having to access the little switches in the back of the drive.

The drive also has every chip socketed. That is a lot of trouble to go to. The sockets are various types. I have never seen the odd tall ones before, the blue ones are pretty, but I haven’t had any of those either, although I have seen similar ones. With the standard black ones, several are cut down, which isn’t that uncommon. The chips are quite a mix of dates, the 6522’s are Rockwell chips not the MOS brand ones I expected.

Two other items that were interesting, the pins on the board that the floppy drive connected to were all bent backward a measured bit. Also the metal shield below the drive had triangles cut off the back. These modifications seem to have been done so that the “drive” unit could be pulled out without fully removing the front panel.

All of these things together indicate to me that this drive was very likely from a Commodore computer repair shop. I see no other good reason to socket every chip on the board, and the odd collection of sockets used seems to indicate it was done with what was on hand. I can see where that would be useful in a repair shop to quickly change the device number from the front, otherwise I don’t see much of a reason for that, the 1541ii already has easy to use switches in the back unlike the full sized 1541. The cut shield and bent back pins that made the drive unit easier to remove don’t make much sense unless you happen to be removing the unit a lot, so that may also indicate it as used in a repair shop as well.

I was somewhat surprised about it not being noticeably yellow. It was a bit dirty and had that clear tape and residue on the vent area on the one side. It cleaned up pretty well, although it has a fair number of scratches on it.

Cleaning

It seems to be figured out overall, so I cleaned up the case, drive and mainboard. It was mostly light dirt internally, but there were a few areas on the mainboard that looked to need a bit cleaning.

To cleanup the case I first peeled the old tape off the side. Then I just started off rinsing it down with water. I then used some Baking Soda with a little water on the wet case to make a paste and an old toothbrush. I figured I would work on the scuff marks first and that actually removed the last of the tape adhesive. The 1541ii has a nearly smooth finish unlike the original 1541s with their rough texture. Due to the relatively smooth finish there is the risk of scratching on the case with the Baking Soda, but this case was badly scratched to start, so I was not worried. I would have otherwise used something that wasn’t abrasive to start. While not very abrasive Baking Soda is a mild abrasive. The Baking Soda and water scrub cleaned nearly all of the dark marks from the case. I then washed the case with regular dish soap and a paper towel to get rid of any remaining Baking Soda. Next I dried the case parts.

From there I moved on to cleaning the mainboard. To clean it I used a ESD Safe black brush to knock away as much dirt as I could. Next I used some 91% Isopropyl Alcohol with cotton swabs, and again the ESD Safe Brush to scrub it. That cleaned the remaining old dirt pretty well. There wasn’t much flux on the board, even though the chips had all been socketed. It seems whoever did that cleaned the flux off at the time. There was only a bit around the power switch and serial sockets etc.

I moved on to cleaning the metal shield that the mainboard sets in, it was mostly dust it out and then I did clean it up with a bit of Isopropyl Alcohol. The odd device switch on the shield had some flux where it was soldered on When I cleaned that it seems the one side was only being held by the flux so it started to fall off. I fixed up that and resoldered it back to the shield. I also straitened out the shield a bit where those triangle had been cut off at the back to make it look a little better.

I then cleaned the drive unit itself. It had light dust in it which I removed with the brush. I cleaned the head again with Isopropyl Alcohol and a cotton swab. I also removed the top plate to get all of the dust out from the area the disk slides into.

Repair & Assembly

Well mostly this drive seemed to be in pretty good order except that missing switch and the reattaching of that device switch that started to come off during cleaning.

I had to replace the JiffyDOS switch. For that I used the drill press with a 1/2 inch Forstner bit. These bits do a great job drilling clean holes in plastic cases if you go slow. They can not be reliably used for this kind of thing with a hand drill though. I set the drill press for the lowest speed setting and go very very slowly. I take light shavings and light pressure. You can use a Step Bit, which are actually intended for thin materials like this though. If you go too fast it will melt the plastic and not cut it properly and will risk pushing through and cracking the case. If done properly you get a very clean hole.

Now that I had the switch installed in the case, I started to reassemble the drive. The drive was missing several screws, so it was time to pull out the spare screw bin and find some replacements. I replaced the three that hold in the mainboard. Once that was in place I soldered the wires onto the new switch. I then used some Kapton tape to secure the wires out of the way so they wouldn’t get pinched somewhere. You can also see that I glued the JiffyDOS label back to the EPROM, I put on a piece of electrical tape first in case the glue didn’t hold well.

Here is a full view of the board. It looks a bit neater than when I opened it up.

Another oddity is the Paperclip on the top of the latch arm. I couldn’t tell what the intention of it is. It puts very little tension on the arm. I think it may be to prevent the arm from flying too high if the front plastic part is not installed. It may be that it could snap something. I did adjust it a little so it rested right on the unlatch arm without adding any additional force.

I like how the new switch fits in pretty well and is not very obtrusive. I did fire the drive up after getting the board and drive unit cleaned up. It was working to read disks. I didn’t have a proper power supply though, so I just verified basic operation. The JiffyDOS switch also worked. I may post some more on this drive once I get the power supply finished up and do an alignment check and such. So hopefully she will still work then. I don’t have JiffyDOS for my Commodore 64 or Commodore 128 though. I may order it at some point if this Drive works out well.