Starting point

This Commodore 1541 floppy drive is in for some refurbishment. The floppy drive is part of a bundle of two drives, where the owner has previously informed be that both of them have various problems of reading. The idea is to try to use both of the drives as a source for parts to make one drive functioning. But we´ll see as we go along where this floppy drive takes. Old computer gear always give surprises - either good ones or bad ones.

From the outside the floppy drive looks to be in very good condition. There are some signs of use (and some dirt), but this is what to be expected after 35+ years of age. The front of the drive reveals that this is (most probably) an ALPS drive. This is a good sign. Compared to Newtronics drives the ALPS drives are more likely to have a working R/W head.

The front badge is partly loose, but it does seem to be undamaged as far as I can see. Only thing is that the metal is slightly bent, but that should be fixable. And... how cool is this... the plastic film covering the badge appear to be still on! I will leave it to the owner to decide if it should be removed or not. The yellowing is not bad at all, but I still think that it would benefit from some retrobrighting as part of the refurbishment.

But there is something which concern me a bit: there is a small rattling sound inside the floppy drive. Something is loose inside. It does not sound too serious, but it needs to be investigated.

Below are some pictures of the 1541 floppy drive before refurbishment.

Refurbishment plan

WARNING: Refurbishing a 1541 will require working on a device connected to live power (230 V / 110). Danger! Risk of electrocution!

To refurbish this 1541 disk drive the plan is to do this trough the following actions (some of them in parallell and different order). Actions in square brackets are performed if required.

STAGE #1: Cleaning, inspection and repairing

- Clean and (retrobright) the exterior casing
- Clean and inspect the PCBs (mainboard and motor unit)
- Clean the interior and lubricate moving parts
- Initial testing
- [Repair mainboard]
- [Replace drive belt]

STAGE #2: Replacing old parts and rewiring

- Replace electrolytic capacitors (PCB-motor unit)
- Replace electrolytic capacitors (PCB-mainboard)
- Reconfigure transformer input from 220 V AC to 240 V AC

STAGE #3: Testing

- Verify drive operation by testing the drive with normal Commodore 64 usage

STAGE #1:

Cleaning and inspection

Disassembly

To start disassembling the 1541 floppy drive the four Phillips 3 x 10 mm machine screws are removed.

With the four screws out of the way, the top cover is lifted away. The PCB, and parts of interior mechanics, are now revealed. There are some sign of dust and grease in here. I immediately notice that this floppy drive have probably been repaired earlier since a few of the glue logic ICs are in socket.

Remember the rattling sound? I don´t see anything immediately. No loose metal- or plastic parts laying around. But when I turn the floppy drive upside down, something falls out... which is a... eh? stone? See picture below and decide for yourself. Ok, not a huge rock, but a small 2 mm piece of something...

To remove the PCB from the drive mechanism seven screws needs to removed (3 x 6 mm Phillips). Note that there is a toothed lock washer on each of the screw. This is to secure that the PCB does not move while the floppy drives operates (the vibrations in a 1514 floppy drive are significant). There are five screws at the top side of the PCB and two screws mounting the voltage regulator heatsink at the side.

Before the PCB can be lifted, the six connectors need to be detached. WARNING: It is good practice to make a note on how these are connected. If these are connected in the wrong orientation, you are running a big risk damaging the R/W head, motor unit controller and the mainboard itself.

When the PCB is lifted away, the interior mechanics are revealed. And it looks very - VERY - good! I can not see any immediate signs of corrosion, and there is very little dust. There are some dust and grease, but it is really marginal.

Nearly there. The large interior metal tray holding the drive mechanics is fastened to the bottom cover with six 3 x 10 mm Philips sheet metal screws.

The interior tray is lifted away from the bottom cover and the cover is revealed. Also here, there is very little dust and grease.

The LED is removed from the bottom cover. This is done in three simple steps:

• The inner plastic ring is loosened

• With a firm push the LED is pressed from the outside towards the interior until it pops out from the LED bracket

• The LED bracket is pushed firmly from the inside towards the outside until it pops ut

The last stage of the disassembly is to remove the floppy drive mechanism from the inner bottom tray. The floppy drive is held to the metal frame with four 3.5 x 9.5 mm Phillips machine screws (two on each side).

As with the bottom cover, the inner metal shield is in fine condition. No signs of rust, and hardly any dust and grease. Also the transformer seems to be in good visual condition.

Exterior casing

"It´s time to take a bath!". The covers are not at all bad looking, but they would benefit from a good cleaning. So the covers are placed in mild soap water for about 24 hours.

After the long bath the covers are wiped with some isopropanol which removes the toughest dirt spots. The covers looks very nice after cleaning. NOTE: Signs of use, such a small cable burn mark and some lighter areas, are more visible after cleaning. These were previously covered by dust and grease. But they are not very visible in normal daylight, but here are the nonetheless. I am not entirely sure how much effect a retrobright will make, but I think I will do that anyway. Below are some pictures of the covers after proper cleaning - but before retrobrighting.

A trained eye might notice that the four rubber feet at the bottom cover are removed (by using a thin flat screwdriver). The reason for this is that these rubber feet will get like "meltet glue" from the retrobrighting process if they are not removed. Also, before the retrobrighting the metal badge is removed. This is not stritcly required, but since I will try to flatten the metal badge, and install some double sided tape at the back, it is easier to remove it. By using some hot air from a hair dryer, and some prying tools, the badge come off quite easily.

PCBs - Inspection and cleaning

There are two PCBs in the 1541:

• Mainboard with most of the logic

• A smaller PCB used to control the speed of the spindle motor

Visual inspection (mainboard)

This is a PCB No. 1540050 (Rev C) / MDK 25 HB mainboard. All the ICs are present, and there are no obvious signs of leakage from the electrolytic capacitors. But there are two things which needs investigation:

• Just next to pin #2 of UC6 (74LS00) there seems to be a small pitch of corrosion (?). I am not really sure what this is, and what caused it, but it does look like one or two traces surrounding UC6 are broken. But could this be intentional? That a small hole has been drilled at factory time? By reading the next to bullet points you can see why ask this question.

• Four of the glue logic ICs are in sockets (UA1, UB1, UC5, UD1). At first I thought that this was due to a previous repair, but I am not so sure any more. At the back of the PCB there are not much signs of repair work. Of course, the repair could have been done very professional, but you often see some signs of rework which I do not see.

• On the bottom of the PCB there are some bodge wires. Even if this might not look very professional I think that this might be from factory. Mistakes in the PCB design could easily have been corrected this way. NOTE: some of the bodge wires are connected to UA1 and UB1. So you could argue that this is actually re-work from a repair, but the solder points on these ICs does not give away any of such signs...

Below are some pictures of the mainboard before refurbishment.

A close-up picture of the cut/broken trace area around pin #2 (U6) below. I am starting to think that this is intentional, but I am not sure if this is done at factory or related to a later modification.

The reason why I start thinking that this broken/cut trace is intentional is that one of the bodge wires are directly soldered to pin #2 (UC2). See pictures below. Also, below is a close-up of the rest of the modification. Unless the drive fails during the initial testing I will leave it like this - assuming this is a fabric modification.

In the table below is a list of all the main chips installed on the mainboard. Note that it is normal that several of the chips were socketed at production time - so this is not a sign of rework.

Visual inspection (Spindle motor speed control unit)

The motor speed control PCB is found on the underside of the floppy drive together with the flywheel and drive belt. This is a PY117 revision of the PCB which is quite common. The PCB looks to be in good condition - it is somwhat sticky and dirty, but I can not see any sign of corrosion or damage.

There are two screws holding the motor unit PCB to the chassis (see arrows in picture above). These two are removed and then the PCB is lifted out from the drive. As seen from the picture below, this PCB is full of sticky flux residue. This is not a real problem, but it is good practice to clean this off. Anyway, the backside of the PCB looks to be in very good condition also. No sign of corrosion or other damage.

Both the front and the back of the PCB are cleaned with isopropanol on a Q-tip/tooth brush. Note that the front of the PCB does "look" sticky still, but it is not. I appears to me that the top of the PCB is covered with some kind of layer which makes it "look" sticky. Below are some pictures after cleaning.

Interior mechanics

This floppy drive is equipped with the ALPS drive mechanism which reputedly is more reliable than Newtronics drive mechanism. Not of the mechanism itself, but the R/W head is less likely to go bad.

Visual inspection

The drive mechanism looks to be in quite condition. There is the usual amount of dust and grease (and it is more dirty than it looks - pictures does not give it justice).

Banner picture credits: Medvedev