Commodore 64 New Powersupply

I purchased an old Commodore 64 Breadbin style computer in December, and it didn’t come with a power supply. That is not exactly a bad thing as the old power supplies are responsible for killing a lot of C64s over the years. When those supplies fail, they often start sending to much voltage into the 5Volt line burning out many of the chips on the board. To see if it made sense to try to bring this old C64 back to life, I hooked it up with a 9Volt Ac Transformer that I had in my spare parts, and my regulated variable power supply. It sort of worked, it did need repaired, but that will be a post for another time.

I did manage to repair the Commodore 64, so it was time to make a proper and safe power supply for it. I took my 9Volt 1Amp Transformer (well 9.5Volt ) and picked up a new Mean Well RS-15-5 5Volt DC 3Amp power supply. I also picked up an enclosure, 4 conductor wire, and finally a proper DIN power connector from console5.com. The other items I had around, the IEC power jack, power cord, fuse holders etc.

I cut an opening in the back of the enclosure for the IEC power port. I also drilled the front for the outgoing power cord and installed a rubber grommet to protect the cable. I used my small drill press to start the holes then for the IEC being obviously not a circle, I trimmed out the rest with my Dremel and a hobby knife. The material the case is made of is reasonably soft and not too bad to work with. Just don’t try to drill or cut to fast, let the tool do the job.

The bottom of the case had some standoffs for mounting. I cut a piece of raw circuit board material to fit into the bottom. I then drilled holes to put screws into it to hold it to the standoffs. This let me have a solid base to attach the heavy transformer and power supply to without putting holes through outside of the case itself. I then mounted the Mean Well supply and the Transformer to the board and installed it into the case.

I really should have the mesh/screen grounded, that is not shown here though.

In the top I mounted a fuse holder, and later a power switch beside it. All of the exposed connections were sealed with Liquid Electrical Tape on the IEC port and the little bit at the base of the Fuse holder that wasn’t covered by the heat shrink for added protection if someone ever opens it up. I also cut out a fairly large opening for ventilation. I figured if I was going to open it up, I might as well make it worthwhile. I had a piece of screen from an old computer case and cut it down to fit and shaped it to bulge into the opening. I don’t know that much heat will be generated, but it certainly should have enough passive cooling going on with that much ventilation. The grill is pretty small, so the odds of anything falling in should be minimal. Also with all of contacts well insulated it shouldn’t be a problem. Something could get in the screw terminals on the Mean Well maybe. To put in the grill, I started by drilling in the corners for the opening with a Forstner Bit with my drill press to make the rounded corners of the hole. I then cut the rest out with the Dremel to get it close and then a utility knife and such to try to keep it clean and strait. It is slightly out of square, but still looks pretty good overall. Of course I did test the supply before attaching it to the Commodore 64.

Here is the completed supply after I added the power switch.

Here is the supply after I finished assembly on the Commodore 64.

It was a relatively simple project. It also was not very expensive overall. The Mean Well was pretty cheap I believe $10.00 with shipping. The next was the case which was around the same price. The 4 conductor wire I used is not very flexible, but even with what I purchased it ended up being more that $20, although I do have a good bit of wire left over. The wire is a stranded alarm system wire, it is only a couple strands and not very flexible. I would also probably crimp badly if it is wrapped up tightly. I figured if the wire becomes an issue, I will end up replacing it with a more appropriate wire. Overall I may have not saved all that much money making it myself compared to the cost of some of the units available theses days, but it certainly means more to me knowing I made it myself. There is not a Commodore 64 Saver circuit in it, but the Mean Well supply does have protection built into it. I did purchase a Commodore 64 Saver kit that I thought of possibly adding to the unit, but I did not have enough space in the case to get it in there. I did later build up the Saver kit, but the trigger voltage drifts with temperature changes. I don’t feel confident the Saver circuit would be all that reliable.

I’ve built a second Commodore 64 Power Supply and done some minor changes/additions. It is a near direct copy of the first model, with a few corrections to make some items easier or better, fuse placement etc.

Commodore 64 New Powersupply 2

1541 two to one

I recently picked up an old 1541 Commodore Disk drive for my Commodore 64. It was a bit ugly so I cleaned it up on the outside and inside before testing it.

I started by taking the case off of course as seen in the pictures. First I used some WD40 to break down the adhesive on the sticker on the top. Then I tried some Isopropyl Alcohol on the permanent marker, but it did not do much. I guess the marker was protected by the dirt.. I went on and used water and regular dish soap with paper towels and a toothbrush for the grills. From there I went to baking soda with a little water to make a paste to scrub the various black marks and the permanent marker with an old toothbrush. It didn’t get all of the marker but it make a big improvement. I then washed it all down with some dish soap again to get any remaining Baking Soda off the pieces. Once I dried it off, I took 91% Isopropyl Alcohol to the remaining marker, and it was able to take care of it just fine. The case is quite browned from the sun, but I don’t know if I will do anything about that.

Internally it was quite dirty too, but I did not think to take any pictures of it. Here is what it looked like cleaned up.

It looked far better and seemed like it may have been in working order. Unfortunately after I put a disk in it was unable to read it, although it attempted to. It turned out that the read write head of the drive was burned out. This is a very common failure on these Newtronic Mitsumi based drives back in the day due to corrosion in the heads or something. Based on the IC dates on the board it is a late 85 or maybe 86.

Above is a picture of the bad head pulled from the drive mechanism. The unit seems to operate normally in every other way, but new heads just aren’t available. With the head being a common failure I considered the odds of getting another Newtronics Mitsumi drive that had a good head as being a big risk. So I looked around for another 1541 listed as needing repaired that had the ALPS drive mechanism instead.

Well we need parts so..

The parts drive came in, it was reported as not working. It made a noise when plugged in but no lights on the front. I looked at the label here, and being in the US the “220V” just won’t work here. The drive wasn’t getting enough voltage to power the 5Volt electronics. It was getting enough to run the 12Volts for the drive motors though atleast to some degree. There may have been nothing wrong with this drive other than that. Still I picked this up for parts. The drive unit itself actually, as this is the ALPS style unit. The drive units are fully compatible, and it is just a matter of pulling the unit and putting it over into my other drive that had the bad head for the Newtronics drive.

220V on the left 117V unit on the right.

While I was in there I did look at the transformer sections. For the 220V there is a “red” tap connected to the fuse, and for the 117V unit the black wire is connected to the fuse. Both transformers are almost the same model number, and both have red and black taps, with the extra tap insulated. Even though they look about the same, minus the last few bits after the dash on the model number, they are different transformers. I did check if switching the Red wire for the Black one on the 220 Volt would change it over to work like the 117 Volt one, but it doesn’t. The only Voltage conversions I have seen on these drives involved swapping out the transformer, basically like I did. The transformer could be changed, also it would be possible to put in and bypass the existing regulators, or supply a proper voltage that can be regulated down by them.

This ALPS 220V unit has the same board model as the Newtronics.

Here is the board in the Newtronics drive, after I had installed the ALPS drive into it.

The boards are the same revision in both drives and appear to have been built just a couple years apart.

Here is the working drive after installing new Electrolytic Capacitors.

The main 6800uF capacitor was dented, so I picked up a set of new Electrolytic Capacitors for the drive from Console5.com. After testing it the capacitors I found one with a ESR of 40 Ohms, so it probably was a good idea to get them replaced. I also redid the solder at the serial ports and a few touch ups of connections that could have been a bit better out of the factory but were ok.

Here is the combined drive assembled. I did basic testing and the drive did read a disk and format a disk fine. I will look to do an alignment check shortly, but it looks like it should be finally working. I have since cleaned up the case from the 220V unit and swapped the converted 117V drive setup back into it. It is less “brown” overall, and doesn’t have a light patch on the top where the sticker was on this one. It did however have a large sticker on the right side, but still looks a fair bit better overall. The change of case doesn’t look significantly different in a picture so I won’t be positing a specific picture of it.

I have also looked over the board from the 220V unit. Someone tampered with it, I don’t think “repaired” is the proper term. I think they realized the 5Volt wasn’t working and removed it and reinstalled it (poorly), they pushed the traces off of the board. I repaired that and a capacitor they had pulled and very poorly reattached as well as one of the jumpers. I also touched up a few of the original solder joints that could use a bit of attention. I then cleaned the board and tested it. The board seems to operate fine, I didn’t do any extensive testing, but is did respond. I figure it is either working fine, or should be reasonable to repair. At this time I am only keeping it for a spare so I packed it up in an anti-static bag for safe keeping.

I am tossing the idea around of turning the extra 1541 chassis into a Pi1541 & Tapuino. I am not sure I feel right putting extra holes into an otherwise good case though. All of the controls would be on the 5.25″ Plate, but it would involve quite a few holes in the back of the case than are there now.

An interesting 1541ii – Cleanup, Figure out and Repair

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.

First these two loose wires coming out the back.

More Wires, an exposed EPROM, and sockets everywhere, and that interesting switch.

Some diodes on a 4 position slide switch.

Here is where the wires from the switch go. To the Device Select Switches.

Here is a close up of the slide switch and that EPROM, where the two wires in the back lead to.

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.

Looks like I found what the EPROM is. It was up in the motor on the bottom of the drive.

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.

Here is the nice clean hole. It may look a little oblong, but that is the picture angle.

Here is my new latching switch for the JiffyDOS mode toggle.

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.

Here you can see the board reinstalled and wires managed.

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.

Here is a view of the back once the board and case is all together.

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.