Pi1541 in 1541 Case & Tapuino – Part 3 : Schematics and a bit

I wanted to post the final Schematics for the Pi1541 Option B+SRQ and Bare Tapuino here.

Gerber Files for the board can be downloaded from here:

https://github.com/Markeno76/CommodorePiTap

Below is the Bare Tapuino schematic. It is basically a Tapuino using a bare ATMEGA328 instead of an Arduino Nano etc as the base. The ATMEGA is burned with the Arduino Uno boot loader. It can be programmed by pulling it or on the board. The required connections are available on the board by the Reset pin plus and other headers. That is why the Reset pin is there, to make that easier. I didn’t route a regular ICSP header though. It was hard enough to route this board for me, and I believe the other header with the required pins would have had to been unplugged for it to succeed. There has not been any firmware update for the Tapuino in a good while either. The design is a combination of the schematics from the Tapuino Github. The C2CON header is for the secondary Cassette for recording from it. I did not use that, although I do have the header in there on my board I have no connector anywhere to accomplish it. Because I am not using that feature, I really don’t need the 4052N on my board. That is what it is for. The 4052N can be bypassed by putting two jumpers in its place. The first jumper goes from Pin1 to Pin3 on it (Write Signal). The second bypass jumper goes from Pin12 to Pin13 (Read Signal). The Tapuino is a Tapuino 1.5 plus the Read and Write LEDs from the Tapuino Mini 1.02, and then using a bare Atmega instead of a Arduino Nano or Mini etc. I could not find schematics for the later Tapuino versions, I guess someone else made them to sell and has not released them. I didn’t care for a buzzer or speaker attached to hear the playback, so I was fine without that. I really do not have the Read or Write LEDs on my board at this time as they were added later. I might add them, but I am not sure it is worth the trouble. I would have to take my control panel apart to get them installed, my thought is to place some surface mount LEDs just behind the mesh. The other thing I would like is there was another firmware out there that had some “graphical” look to the Tapuino LCD display, I would really prefer that. I can’t find it anywhere, it was posted on a German blog I believe, but only pictures of it, no code etc.

The other note on the 4052N is that the 74HTC4052N does not work, but a 74HC4052N does work on the Tapuino.

Being a “Bareduino” base, there are other components on the schematic that are not typically on a Tapuino. That is because most are based on using one of the Arduino boards as a base. It was a good excuse for me to make a Bareduino.. I figured why waste an Arduino Nano or something like that if I was making a board anyways.

Pi5141 Option B + SRQ and TFT LCD Passthrough header.

The above is the Pi1541 Schematic. It is Option B plus with the addition of including the SRQ signals. They will be required for some updates to the firmware to take advantage of.

The TFT LCD Passthrough is probably less useful to most, it is actually a traditional Mini Din PS/2 Port. That is what my little 7″ Composite LCD came with as a connector. I decided to put it into the Tapuino. It was originally for use on my workbench to test my Commodore 64. It supports 2 inputs, the default is the one connected to the Pi’s Composite video output. The second input is out the back of the 1541 case and can be connected to the Commodore 64 Composite Video output. The board footprint and setup is actually setup so as to allow putting a Second Serial Din port side by side with the first one. If that was the case, then the TFTLCD header would be wired over to the back of the Serial port and the Serial Din would be installed instead of the PS/2 style Mini Din.

The 7″ LCD though lets me use this device as a stand alone device with the Pi, or with the Commodore as a reasonably portable LCD. There is also a jack on the back of the 1541 for an Audio Input with a switch beside it. If the switch is flipped toward the jack it will output the audio from the external jack to the internal amp and speakers, if it is switched the away from it then the audio is connected to the Pi’s audio output instead. This lets me play the Pi sounds through the internal speakers. The speakers are actually Mono, the rear jack is mono too. The Pi audio output is mixed down to mono with a resistor to prevent them back feeding into each other and damaging the Pi’s audio output. The alternate is that I can again connect up the Commodore 64’s Audio Output to the internal speakers.

The MicroSD Cards are both accessible from the front, the one on the left being the Pi’s card slot, which is extended with a MicroSD extender. The one on the right being the Tapuino’s card. This lets me remove them to add or remove files easily. The other thing it allows me is to swap the card in the Pi. I can then use the Pi for more things like running Raspbian on it, I can then output that to the internal speaker and the 7″ LCD. It can alternately access the HDMI Port on the side of the case (again with an extension going to the Pi itself). I can also put in a card with RetroPi on it, which again can run on the internal speaker and 7″ LCD or alternately output through the HDMI. I can then connect up controllers to the USB ports that are accessible on the side as well.

There are plenty of variations on the design possible. My point was to reuse this case I couldn’t otherwise make use of due to the failed read write head on the unit. The transformer I had left was for 220Volt input, so that wouldn’t have been of use to me either. I wanted to do something with it that would fit in with my C64, and there was just way to much extra space to not make more use of it. I liked the idea of doing a Bareduino project as well.

The Cassette cable worked out really well to. It is basically wired up as a passthrough Pin 1 to Pin 1 from the Din to the Card Edge connector. The Card Edge end is bolted into a DB15 (Gameport type not HD15 VGA (which is DB9 sized)) shell. I later painted it with a Green “Top” mark and lines and a Red “Bottom” mark so that I know which side should be up. I also inserted a bit of plastic to work as a Key into the slot in the connector. I had done that before and it fell out, so i wanted to have a visible mark as well. The wire is part of a very flexible Cat5 cable (yes old Cat5 not Cat5e) that I came across, I pulled out the extra 2 wires to make it more flexible as well. The ends have some heat shrink on them to build them up slightly and provide some strait relief.

Above you can see both the 7″ LCD and the little OLED on the drive face both display the Pi1541 output. So it can be used with or without the 7″ attached. The Pi controls are there on the left side, the 3 buttons and the 2 way momentary toggle switch. The Red LED is the Pi1541 activity light. The Green led on the left in the factory location is the Pi1541 power LED, it lets you know the Pi’s power is turned on. The other Green LED on the front panel is actually the Power LED for the internal audio amp. The Red tipped knob is the volume control and On/Off for the Audio Amp. The 4 buttons on the right are the Tapuino controls with the small LCD on the right being the Tapuino display. The Tapuino is powered completely by the Commodore 64 Cassette port. So the main power for the Pi does not need to be on for the Tapuino to work. That is partly why there are 2 schematics. There are two 5Volt power sources, the one that Pi uses is the internal Meanwell power supply where the Tapuino section receives the power it uses from the Cassette port, they are not wired together. They do share a common ground, which they share through Serial connection anyways.

I have used this unit for Raspbian as well as Retro Pie as well. My general intention is to use it just as a Pi1541 though most of the time. Originally I figured I would use it for Retro Pie a bit as well, but I have since built a Bartop Arcade to run Retro Pie instead. I really didn’t feel like disconnecting it from the Commodore desk and moving it to the living room to connect to the TV and such just to play some old games (other than Commodore games that is).

I have been thinking of putting a button on GPIO3 for a safe shutdown and startup button for the Pi when using Raspbian or Retropie like I did with my Bartop Arcade build. I just don’t at this time know where I would want to put the physical button. I could reuse one of the Pi1541 buttons, I could assign Safe Shutdown to another GPIO Pin that they happen to already be connected to. Still that would then not work as a wake up button as GPIO3 is the only one that will wake it.

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.