Alps, Munich

#Sidecar

Sidecar Restauration, Part 3

In the third and final part, I am going to futureproof the Sidecar and finally test it. Will it work after all the hours and patience I put into the repair?

Gotek Drive

I probably only own a single 5¼" floppy disk, back from my time at school. However the Sidecar won't do much without floppies, so I decided to add a Gotek drive.

The modification must be fully reversible, and I also wanted to keep the original look of the Sidecar with its floppy drive. I designed a Gotek bracket for the expansion slot and a control panel with OLED display and encoder. The panel is screwed to the front air grille, so no holes need to be drilled into the case.

The Gotek bracket on the expansion slot. The control panel, ready for mounting. The control panel, mounted to the front of the case.

I made a new flat cable to connect the Gotek drive and the floppy drive to the mainboard. The Gotek drive is supposed to be drive A:, while the floppy drive should be B:. Both drives can be configured with jumpers, so there is no need to make a twisted floppy cable.

First Test Run

For the first test run I did not connect the Sidecar to the Amiga yet. If something on the Sidecar was badly broken, it wouldn't damage the Amiga that way.

So I turned on the power. The fan spun up, the power LED lit up, but nothing else happened. Well, since the Sidecar is not meant to work as a standalone PC, this is probably normal. At least there was no magic smoke and no smell of smoldering electronics. I took the opportunity to check the voltages, and they were all correct and stable.

Things looked pretty good.

Making a Janus Workbench

The Sidecar is controlled by the Amiga. It has no connectors for a monitor or keyboard. Fortunately, the driver disk can still be found on the internet. For installation, I first had to make a copy of the original Workbench 1.2 disk, and then run the installer from the install disk.

On my Amiga 1000 however, the installation failed because the RAM disk ran out of memory. My Amiga is equipped with the maximum 512KB of Chip RAM, so it was supposed to work. I tried it multiple times, but always got this strange error.

I gave up and set up a UAE instance of an Amiga 500 with Kickstart 1.2 and 2 MB of Fast RAM. On this machine I was finally able to complete the installation.

The installer is a bit strange and not based on the Amiga installer tool that came later. It is best to use the default options and wait patiently for each step to complete.

Test Runs and Fixes

My test configuration, with the Amiga 1000 and the Sidecar. It takes a lot of space. It's finally time for a real test run.

Connecting the two devices isn't easy and can damage the hardware if done wrong. First I unplugged the power cords from the Sidecar and the Amiga. Then I connected the Sidecar to the expansion port of the Amiga. It's a bit tricky to find the correct position, but the joystick and mouse connectors are a good orientation guide. There is no need to use force.

The Sidecar also has a power cord extender. I plugged it into the Amiga's power connector and made sure that the Amiga's power switch was turned on. Both devices can now be controlled with the power switch of the Sidecar.

CAUTION: You must never turn on power to the Sidecar unless the Amiga is already powered up. Otherwise you will damage your Amiga! You can avoid this problem by using the power cord extender and making sure that the Amiga's power switch is always on.

Now it was time for the truth. I booted the Janus Workbench I prepared above, but got a Guru Meditation during startup. I tried other driver versions and other floppy disk images I could find, but it always ended with the flashing red square.

Fortunately, the hardware registers are well described in the A500/A2000 Technical Reference Manual, Section 4.1. The description is for the A2088XT bridge board, but it is very similar to the Sidecar.

I quickly hacked some small diagnostic tools. They confirmed that the 128KB bridge RAM and the six replaced bus drivers were working fine.

I also found that the PC reset did not work. I only managed to actually reset the PC once. It played a chime and then actually accessed the MS-DOS disk I had in the Gotek drive. This means that the PC side was basically working, but the bridge board was having problems.

There are four PALs and three FPLAs on the upper board. The PALs have a specified memory retention time of about 20 years, which is long past. I remembered that the PALs on my MaestroPro were already having memory problems due to old age.

The fusemaps of the PALs can be found on the Amiga Wiki. I replaced the four PALs with modern ATF16V8C-7PU GALs.

After that I was able to reset the machine reliably. The Guru Meditation was also gone when I booted the Janus Workbench. But the Sidecar still refused to come back out of retirement. What I got now was a garbled PC screen.

No Guru Meditation, but the screen content isn't good yet.

But I was on the right track! There is also a single PAL (and two FPLAs) on the lower board. I replaced this PAL as well, and also replaced the ribbon cables that are connecting both boards. The original cables still looked good, but the wires may have been damaged or corroded, and replacement is cheap.

The Sidecar with the replaced PALs and new cables.

Next attempt. And finally, this time I was successful! I tested the machine for about an hour, formatted some floppy disks I bought somewhere, started Turbo Pascal. Everything worked reliably, and it was impressive to see MS-DOS running in one Amiga window and still have the full power of Amiga's multitasking to run Amiga software.

MS-DOS in one window, Amiga Workbench and Clock in other windows.

I was lucky. The PALs were easy to replace, as compatible GALs are still being produced today. The FPLAs can also potentially lose their programming, but there are no modern replacements. Mattis Lind designed a replacement board that uses a modern CPLD, but there are no corresponding JED files for programming them.

And there it is, my fully restored and futureproofed Commmodore A1060 Sidecar!

The Sidecar, fully restored, and with Gotek controller.

The restoration was much more difficult than I expected. There were many bad surprises waiting for me, and more than once I was close to giving up the project and storing the Sidecar away for later.

This beast is difficult to repair. First of all because of its size. The Amiga 1000 plus Sidecar was too big for the table in my tiny workshop, so I could not use my scope. Also there is not much use in running the Sidecar alone, so you always need a running Amiga 1000 for troubleshooting. Third, it's hard to find a place to put the Sidecar's PSU while probing the boards. The open nature of the PSU also poses a risk of electrocution if accidentally touched. All in all it was an interesting experience and I have learned a lot about Commodore bridgeboards in general and the Sidecar in special, but I probably wouldn't do it again.

Sidecar Restauration, Part 2

In the first part, I disassembled the Sidecar. In this second part, I will fix all the broken things and put the Sidecar back together in its original state.

Let's start with the mechanics. The floppy/PSU frame had some rust spots. I used a sanding machine to remove them all. Then I used zinc spray to protect the metal and restore the original look. The result was much better than expected. The frame now looks almost links new.

The PSU/floppy frame, coated with fresh zinc.

I got the overhauled PSU back. @DingensCGN, who already overhauled my Amiga 1000 PSU, did an excellent job again. He replaced all electrolytic capacitors and the power filter, removed the luster terminals and inserted a new pull relief. I also asked him to add a connector for a 12V fan. The original fan was a 230V model and was said to be awfully noisy. I never liked noisy computers, so I will replace it with a modern 80mm Noctua fan.

The overhauled PSU without the metal cage.

I'm always relieved to know that a power supply is safe to use, properly grounded, and won't damage the machine or electrocute me. 🙂

I was also lucky enough to find a Chinon FZ-502 at an online auction. This type of floppy drive type was commonly used in a Sidecar and would restore the original look of the front.

The PSU in its cage, and the new old floppy drive.

There is a metal shield supposed to be around the floppy drive, but unfortunately it was lost. It's not a required part though, and no one would notice it was missing once the case is closed.

Next problem: The legs of the power LED were broken off and the LED is stuck. I had no choice but to use brute force. I drilled out the LED and the plug that held it in place. I had to be very careful. If I drilled too deep, I would ruin the look of the front.

I then used a new standard rectangular red LED and 3D printed a plug to hold it in place without glue. The new LED is held firmly in place, but could still be removed by gently pushing it out from the front side with a screwdriver.

The LED is drilled out, fortunately without damaging the front. The new LED and the 3D printed plug. The replacement LED is ready to use.

The mechanical part is done. Time for the electronics.

On the upper board only a single electrolytic cap had to be replaced. But it took a lot of unsoldering work to remove the broken Zorro connector and the six bus driver chips. The original Zorro connector was held in place by two rivets, and I had no choice but to drill them out, slightly damaging the board in the process. I then washed the board thoroughly with IPA.

The upper board: cleaned, recapped, new Zorro connector, and the six driver chips seated in sockets.

There was also a tantalum capacitor, which I replaced with a new electrolytic one. This is not really necessary, but I don't trust old tantalums. They cannot leak like electrolytic ones, but they can catch fire or explode, causing even more damage to the board than electrolyte.

On the bottom board, there were ten electrolytic caps due for replacement. I also replaced the rusted piezo buzzer, which was a bit difficult because the new one turned out to be surprisingly sensitive to heat.

I don't like empty sockets, so I organized an 8087 FPU. Eight 41256 DRAM cells will upgrade the machine to the maximum possible 512 KB RAM. (The famous 640 KB can only be reached with a RAM expansion card.)

The installed Sidecar V2.06 firmware was the latest version I could find, so I just gave the original EPROM a new label, as the old one came off because the glue had dried out.

Lower board: Recapped, new piezo, new FPU, DRAM fully extended.

The board needs a new configuration after the change. Fortunately the original manual can still be found.

I also replaced all screws with new ones.

And finally, it's time for reassembly. Probably for the first time in decades, the Sidecar's case was closed again.

Lower board, back in the case. The reset line is reconnected. Floppy/PSU frame and upper board (below, not visible). The screws of the new fan are still missing. The restored Amiga 1060 "Sidecar".

Isn't she a beauty? 😍

That's all for the second part. If you've been following my article closely, you'll have noticed that I haven't turned on the machine yet. That's right. I avoid powering up old computers without at least having the PSU inspected, because there is a risk that (after decades of storage) the PSU is defective and could damage the machine or go up in smoke.

In the third and last part I will connect the Sidecar to my Amiga and finally find out if it works.

List of Capacitors

Lower board:

  • 2x 100µF 16V radial
  • 8x 47µF 25V radial

Upper board:

  • 1x 100µF 16V radial
  • 1x 47µF 25V radial (as replacement for the tantalum at C57)
Sidecar Restauration, Part 1

Front view of the A1060 Sidecar, but with a gaping hole where the floppy drive is supposed to be. I was lucky and got hand on a Commodore A1060 "Sidecar". This first part is about the teardown of the Sidecar, and the damage assessment.

But what is a Sidecar? When Commodore released the Amiga 1000, its graphics and sound capabilities were unmatched in that price range. However, because the machine was based on the Motorola 68000 processor, users were unable to run existing MS-DOS software on the machine.

The German Commodore factory in Braunschweig tried to solve this problem with the Amiga 1060. The machine was connected to the Amiga 1000 and provided a full IBM compatible PC. Although it was a standalone computer, it had no video and keyboard ports, but was fully controlled by the Amiga. Because it was connected to the right side of the Amiga, it looked like the sidecar of a motorcycle, which gave it its nickname.

The Sidecar came relatively late to the market, could only be used with the Amiga 1000, and was quite expensive. For this reason, only a small number were produced. I could not find any official figures, but according to Dr. Peter Kittel (an engineer at Commodore Braunschweig) only between 3,000 and 5,000 units were sold in Germany, and certainly even less worldwide.

My A1060 came with an open case top. The reason was that the 5¼" floppy drive had been removed, and a full-height hard disk drive had taken its place. It was so tall that it didn't fit in the case, and it was also surprisingly heavy.

The case cannot be closed for a reason. With the case top removed, there is a huge harddisk where the floppy drive is supposed to be.

Many screws were missing or oxidized, but otherwise the machine was in used but acceptable optical condition. The previous owner had added a reset button on the front, and a second D-Sub connector on the back (which later turned out to be a second floppy drive connector, for whatever reason).

I decided to take the entire machine apart for cleaning and damage assessment. My plans are to restore it to its original state, which also means removing the oversize hard drive and its controller board.

There is a frame that holds the floppy drive and PSU. I found a lot of strange rust on it, which looks a bit like moisture damage, but that wouldn't explain the shape of the stains.

A lot of rust stains on the floppy/PSU frame.

The PSU looked okay-ish. Luster terminals were used for the floppy power connector. Also the pull relief for the Amiga power cord was missing, instead I found a knot in the cord.

The PSU looks good, but the caps certainly need to be replaced. A knot as pull relief. Please don't try that at home!

I gave the PSU to an experienced technician at the a1k.org Amiga board for overhaul.

I also found that the pins of the power LED were broken off. The LED was held in place by a superglued plastic plug. It was impossible to remove without force. The replacement power LED was just hanging loosely in the case.

The power LED, with the legs broken off. I couldn't pull it out. The replacement LED.

Let's dig deeper. The computer consists of two boards. The lower board is the PC compatible, with three XT bus slots, a socket for the FPU, and eight sockets for another 256 KB of RAM. The upper board serves as a bridge between the Amiga and PC side. Both boards are connected by two flat ribbon cables.

At the first glance, the upper board looked dirty, but otherwise okay. On the bottom side there are a lot of bodge wires, additional resistors, and cut traces. At first I thought that this modification had been done by the previous owner, but then I found similar photos on the internet, so it seems to be a standard post-production factory fix.

The upper "bridge" board. The bottom side shows many hardware modifications.

Then I found that six 74HC245 bus drivers had been replaced with 74LS245 ones. The replacement was a little "creative". The old chips were cut off the board leg by leg, and the new chips were then soldered to the remains of the old legs. This was certainly not factory-made.

On the one hand, I was glad that the previous owner did not try to unsolder the chips, as he could have damaged the board. On the other hand, it looked very DIY, so I decided to clean up the mess later.

The driver chips, just soldered onto the board.

Replacing the 74HC245 with 74LS245 turned out to be a common fix to make the Sidecar more compatible with Amiga memory expansions. I decided to keep the 74LS245, but to use sockets so that it would be easy to undo this modification.

I also found that the Zorro connector was unfortunately damaged beyond repair. Two pins were broken off and another one was bent so it could cause a short.

Closeup of the damaged Zorro connector.

It was impossible to find a replacement 88-pin edge connector that could also be riveted to the board, but I did find a new connector of the correct size but without the rivet holes.

The lower board was even dirtier, but otherwise seemed to be unmodified and undamaged. The buzzer, however, was rusted, so I would have to replace it.

The lower "PC" board, dirty but otherwise okay.

In the end, there is a lot of work to be done:

  • Clean the case, remove the rust, replace all screws
  • Fix the power LED
  • PSU overhaul
  • Replacing all electrolytic caps, the buzzer, and the Zorro connector
  • Clean up the six bus drivers at the upper PCB
  • Find a new floppy drive

More of this in the second part of this article!