Acorn Archimedes A3010 repair
I was very fortunate to get this vintage computer from my friend Eric. This Acorn Archimedes A3010 was producted in 1992 by Acorn Computers and was based upon an ARM250 RISC microprocessor. Right away I proceeded to connect the computer to see if it still was in a working condition.
The A3010 has 2 possibilities to connect it's video signal. One is though a 15KHz VGA connector and the other is a RF modulator. As I did not have a monitor that could display video in that range and my other choice was the TV modulator output. After a while of searching for the right frequency, which was 591.25MHz (channel 36) I got a black screen with a prompt that stated: RISC OS 4096K, Supervisor, *. So that was a good sign.
After giving the feedback to my friend, who was an expert on this computer as he has owned it for the past quarter century, he told me that it actually should boot into a graphical desktop environment and I should type *desktop. Unfortunately this resulted in an error File 'desktop' not found (Error number &D6). He also advised me to reset the CMOS of the computer by turning the computer on while holding the delete button. But it still resulted in the same error.
Now I knew that I had to open the machine up and see what is going on. I have seen some pictures of the Acorn cormputer motherboard where the CMOS battery had leaked and destroyed a lot of the circuitry, so I was anxious to know what was going on, expecting the worst and hoping for the best.
The case was fairly easy to open as it was held on the bottom with only 3 screws. After getting them loose I could get under the hood. The inside of the computer was very clean. I have also found a good video on how to open the Acorn A3010.
As addition to the steps in the video I needed to remove the SCSI adaptor that was plugged into the motherboard. This could be done by removing two screws on the side of the card.
Then the card could be lifted up as it was plugged into a stip of DIP connector header.
Next, I have removed the floppy disk cables and the metalic shielding. At this point you could notice some spots corrosion around the parallel port.
You could also see that the battery that was soldered onto the motherboard had a small leak. It had a strange white mesh and some of the SMD components had a green/blue mesh on them.
I took some close up shots and you could actually see that there were crystals formed on the metal parts of the components. Quite beautiful. As Eric was also involved in the rapair he sent me a link on what the crystals could be.
A part of the parallel port was also corroded.
I started to clean up the board with cotton swabs and isopropyl alcohol. I also applied heat to some of the SMD parts and replaced the tin on the connections. They parts were ok, but after probing some connections I found out that there were breaks in the copper traces on the board. I needed to repair them. First I had to remove the bottom shield that the motherboard was attached to. This gave me the chance to clean the rust on the parallel port.
After that I solder the wires that replaced the broken traces. Luckily there are schematics of the A3010 motherboard PCB available online and that helped a lot.
It was time to replace the battery. The CMOS chip on the board is the NXP PCF8583 clock and calendar with 240 x 8-bit RAM. According to the specs in can be powered in the range of 1.0 V to 6.0 V. The original Acorn battery is Varta V280R 1.2V Rechargeable NimH but it is not manufactured anymore. There are some good replaclemnts like Varta Mempac 3V6 150H, but they are rather costly. So I have decided to connect two AA rechargable batteries.
First I have unsoldered the old battery.
Then I have connected the two pack of rechargable NiMH batteries. Maybe with 5000 mAh it will be a slight overkill, but it should work fine.
I have also decided to clean the keyboard. The keys snapped off very easily.
I have put them in the dish washer and let them dry. I left the springs attached as after removing a couple of them I noticed that they were pretty hard to reinsert. Then I started to put the keys back.
They keyboard looked a lot better, but there was still some yellowish glow to them. In the future I am thinking of retrobrighting them.
Now it was time to test the computer. I have tried the power on + delete button combination and the Acorn booted up without any problems! Well.. now I had another problems. To start with I didn't have a mouse, then there was the RF modulated output, which wasn't that great and finally I did not have any software to run on the Acorn computer. Anyhow.. I was extremely happy after seeing the RISC OS 3 boot logo.
In the meanwhile I could start the Task window with Control+F12 and run ARM BBC BASIC V. It is considered to be the best implementation of this computer language ever created.