Owner of a broken Arch.

This means your Archimedes is not happy.

So my purchases from AliExpress finally started trickling in, and, with some sockets from Jaycar I was ready to move forward with trying to fix the Archimedes.

This was very heavily assisted by the always excellent team over on StarDot.

Step 1: Burn off a set of Diagnostics ROMs to allow me to see where the RAM was failing. Everything else would rely on that first step. I downloaded the ROM images and fired up my trusty TL866II+ and burned the ROMs out. One ROM failed, but that was why I purchased them in bulk. They were cheap so no love lost there.

Step 2: Insert the ROMs in the Archimedes. My Archie had an ALA32 ROM expansion board so I very carefully removed it and inserted the ROMs in place. I had to change some jumpers on the motherboard, but it wasn’t too hard to find which ones. (Page 77). With that change in place and the new ROMs in the correct position (With the ROMs to the front of the board with the spare pins towards the back of the board) I was ready to fire it up.

Step 3: Boot up the Archimedes. It actually booted up, which was excellent, and displayed a ROM Diagnostics screen albeit with some corruption.

Well that’s better than nothing!

At this point it was late and I went to bed.

The next day I plugged in my keyboard adapter and fired up the diagnostics again. I pressed ‘2’ on the keyboard and let it run. (I had tried option 1 but I don’t think it liked not having a printer)

OK so we have some issues there

So reading that across I could see some bad chips. It took me a little while and some additional help from the team over on StarDot to translate this.

So first up &55555555 is Hexadecimal so we need to convert it to Binary, which is, unimaginatively a pattern of 01010101010101010101010101010101
We can see that the output we are getting doesn’t match that. We’re getting 010101010101000101010101000101?? (where the last two bits are flipping randomly)
This Archie is laid out using 32 pieces of 1 bit wide 1 Mbit RAM chips, laid out in a 1 to 1 fashion with the 32 bit data lines.
Further to this, the StarDot support team pointed out that on this diagnostic, the least significant bit is to the right.
(Keeping up? Good!)
Now, referring to the motherboard schematics, I was able to construct a chart with the bit pattern at the top (as it was coming out of the system), with the bit being tested underneath, followed by the actual chip number below that

0101010101010B01010101010B0101BB <- Output from Diag
33222222222211111111110000000000 <- Bit number (read down)
10987654321098765432109876543210
86868686868676767575757575757565 <- Chip number (read down)
57463524130291806857463524130291

So, reading down the columns, we see that Bit 0 (Chip IC51) is dead, as is Bit 1 (Chip IC69), followed by Bit 6 (Chip IC54) and Bit 18 (Chip IC61)

I then checked connectivity for every trace to the nearby resistor (All fine), the value of the resistor (All fine at 68Ω) and then from there to the inside of the CPU socket. (All fine).

It was also at this point I was advised that, despite all appearances, the carrier board was, indeed, socketed, so I didn’t need to remove it. Back in it goes. (Seriously! The “socket” I literally mistook for lightly soldered through hole plating. It’s amazing. I don’t want to think how much it must have cost)

Play “Spot the hidden socket”

Time to break out the desoldering gun. Chip IC61 and IC54 both came out without too much difficulty, but the other two were heavily corroded and needed desoldering and resoldering with loads of flux. Once they were out, the top pads were so heavily tarnished I honestly thought I’d killed the through hole plating! Thankfully a quick cleanup with a fiberglass pen revealed the underlying copper. I plated them with a bit of solder and dropped sockets in all 4 spots.

Initially I refitted the original RAM to confirm the faults stayed and weren’t related to, say, a damaged trace. After that, I replaced the “bad” RAM chips, one by one, and one by one the RAM issues went away. Also, the screen got less glitchy each time!

I will admit to a silly mistake at this point. I wasn’t paying attention, and thought one of the RAM chips hadn’t worked after replacement, until I looked closer and realised the “bad” bit had moved! It had passed the first part of the test and found a fifth potential bad memory location.

Less glitches. Changed “Bad” bit location.

Back to my cheat sheet and this time the bit pattern has reversed, suggesting this chip is held low.

1010101010101010101010101010B010 <- Output from Diag
33222222222211111111110000000000 <- Bit number (read down)
10987654321098765432109876543210
86868686868676767575757575757565 <- Chip number (read down)
57463524130291806857463524130291

Out comes Bit 3 (Chip IC70) and in goes a socket and a replacement RAM chip. At this point it actually passed all the tests, albeit with still having graphical glitches.

I tried the original ROMs back inside and it still only booted to a red screen.

Of course, the StarDot team came to the rescue again, by pointing out that I’d only tested the first 1MB. I needed to press “M” twice to expand the memory footprint to cover the full 4MB. So off we go again! Look! More bad RAM!

Lather, Rinse, Repeat.

Now it’s late at night, and rather than risk burning myself, I go to bed, fresh and ready for another attempt the next day. Out with the chip decoder…

10101010101010101010101010B01010 <- Output from Diag
33222222222211111111110000000000 <- Bit number (read down)
10987654321098765432109876543210
86868686868676767575757575757565 <- Chip number (read down)
57463524130291806857463524130291

So Bit 5 (Chip IC71)needs to come out. This one put up a real fight. I had to desolder, resolder and then desolder again each side at least twice, but I got there in the end. In goes the socket. In goes the RAM. I hope this is it. I’m down to my last 2 sockets and my last 4 RAM chips.

Fire it up and immediately it’s obvious something has changed. There’s no graphics glitches. It’s all clean. More importantly after about 30 minutes, it seems to have finished checking without any errors!

Wow that is a lot fuzzier than it looked on the phone…

OK. Out comes the test ROMs. In go the original ROMs. Change the jumpers. Turn it on and… I get a blue screen? What does that mean?

Then I remember you need to reset the CMOS on the Archimedes by holding down the DEL key on the keyboard. I do that and…

Whoa!

It works! It actually works! After all this effort by both myself and the team at StarDot, we got it working! I’ve played with the mouse and opened some of the built in apps and it seems to be working absolutely fine. I’m ecstatic!

I still need to replace a dead capacitor on the mainboard, but after that, it’ll be time to put it back in the case, connect up the HDD and see if it’ll do anything else. Hee!

I did a thing! (Mac SCSI)

It ain’t pretty but it works.

So now I have my Mac SE/30 all nice and stable and set up the way I wanted it set up, I decided it was time to play around with something I built a fair while ago.

Quite some time ago, ty tech patron (Hi Greg!), who has gifted me so much stuff over the years, also gave me a SCSI CD ROM to use. This was a bare drive, but I wanted to see if I could get it working.

To this end I ordered some Centronics 50 way connectors, some 50 way ribbon cable and some 50 way IDC connectors. I also dug out an old Dell SFF PC that my housemate had picked up from a throwout somewhere along the way.

I ripped out everything except the power supply from the case, and wired in a toggle switch. Using some leftover knockoff Meccano bits, (I have had far more fun from it than the kids ever did) I mounted the switch where the on / off button used to be.

I crimped on a Centronics connector and two IDC connectors on to the ribbon, making sure that all the pin ones lined up on the red pin. (Yes I have made a mistake in the past. Why do you ask?)

I then “mounted” the Centronics connector into a card slot spot at the back with whatever I had lying around. Close enough that it doesn’t fall out πŸ™‚

I set the CD-ROM up to be terminated, and on SCSI ID 4 (Where it should be anyway). It was then mounted in the Optic Drive spot in the case. After that it was a simple case of connecting the cable to the drive, the power to the drive and powering it on…
The drive ejected. The drive inserted. Ummm…

This was about the point the Mac PSU switch started arcing so that went on the back burner for quite some time. Then I hit some problems with System 7.5.3. But now the system is super stable, so I plugged it in and…. realised I didn’t have a single Mac CD ROM.

To the burner, Batman!

I burned a copy of OS 7.5.3 (Because I had it on hand) and it showed up! W00t! I have a CD ROM! 1991 me is envious as all get out.

Long term I plan to paint the whole case beige. That way it’ll match the Mac πŸ™‚

Where the Archimedes is at

Well, with the Archimedes, I’ve reached the point where I believe I’m stuck until I can get some ROMs burned with a RAM Test image on them.

What I have checked so far:

  • All RAM chips have power.
  • None are getting hot.
  • All lines to all chips are showing activity. (This took a LONG time)
  • The MEMC chip is clean and the socket for it is clean.
  • The system is consistent.
  • My keyboard / mouse adapter works well.

If I can work out which RAM chip is faulty, there’s a good chance the system should just boot. Unless, of course, the fault is somewhere else πŸ™‚

I used ‘ResEdit’ in anger today…

So I was having an odd problem where I couldn’t install System 7.5.3 on my Mac SE/30, which was driving me a little loopy. I joined a 68K Mac forum and they helped me solve the problem in seconds.

The problem is that I could no longer boot from System 7.5.3, which is the latest version of the software I wanted to actually run. I tried a HDD boot and a FDD boot. Both would lock the Mac hard and require a hardware reboot.

After MUCH fluffing around I asked on the forum where I was immediately redirected to this page. After a few seconds with ResEdit, I had a booting System 7.5.3 install. Yay!

Now to install System 6 and 7.1 followed by Dark Castle.

The Collection (As of 27/04/2021)

A quick document of what equipment I have, and what status it’s in, as of today.

Monitors

  • 2 x SVideo capable flatscreen monitos. Both support Composite, VGA, Component and SVideo. I use these for a lot of my older 8 Bit systems. They’re generic off brand.
  • ACER-V226HQL. These are capable of syncing right down to a 15KHz signal and have a rock solid picture.

Computers

8 Bit

  • Commodore Vic 20, with a smattering of cartridges. Now modded for SVideo
  • Commodore 64c x 3. 2 working, one needs work. JiffyDOS, Floppy disks, Cartridge emulator, FDD emulator, Printers. Uses SVideo for picture
  • Commodore SX64, DEAD. Needs the PSU rebuilt.
  • Commodore 128D, Internal FDD is unreliable, otherwise works fine. PSU rebuilt, Uses SVideo for picture.
  • Sinclair Spectrum 48k, with adapter to allow mobile phone to replace tape drive. Works. Composite only.
  • Apple IIeuroplus, with language card and FDD card. 2 x Disk ][. Works. Composite only.
  • Apple II+ clone. No ROMs.
  • Apple IIe with 80 column card and 128Kb RAM, Serial Card, Z80 Card and FDD card. Duodisk. Works. I also can use a Floppy Emu with this. Composite only.
  • Apple IIe clone. Works. No cards. Keyboard completely rebuilt. Composite only.
  • VTech Creativision. (Aka Dick Smith Wizzard). MultiCart. Right joystick has failed. Long term project to replace it. Modded for composite.
  • BBC Master system. Works. Gotek drive, SD Drive, ROM Upgrade, home made joystick, PiTube. 15KHz video cable.
  • Atari 800xl. Works. 256K RAM upgrade installed. SDrive Max drive covers tape and FDD emulation. Uses SVideo for picture

16/32 Bit

  • Apple IIgs. 8MB RAM expansion, Booti HDD, Duodisk FDD. I also can use a Floppy Emu with this. Works. 15KHz video cable.
  • Amiga 1200. Gotek Drive. Works. Needs a new case to be laser cut. Really need to get around to this. 15KHz video cable.
  • Atari 1040STfm. Gotek Drive. Works. I love this machine. 15KHz video cable.
  • Atari 1040STᴇ x 2, Both upgraded to 4MB RAM. 15KHz video cable.
  • Apple Macintosh SE/30. Upgraded to 20MB RAM, ROMinator II Atom, SCSI2SD, I can also use a Floppy Emu with this. Working on an external SCSI CD ROM but not having much luck yet.
  • Archimedes 440. Currently won’t boot out of BIOS. My big project.

Consoles

8 Bit

  • Nintendo Entertainment Center x 3. 1 works. 800 in 1 cart. Awaiting edge connectors for a second.

16 Bit

  • Sega Megadrive. MultiCart. Works.

32 Bit and later

  • Commodore CD32. Works.
  • Sony PlayStation 2 (phat) with HDD, Network adapter. Works.
  • Microsoft X-Box (original). 500GB HDD. Works.
  • Nintendo 64. MultiCart. Works.
  • Nintendo Wii. Works.
  • Microsoft XBox 360 x 2. Works.
  • Sony PlayStation 3. Works
  • Nintendo WiiU. No longer works, alas. I need to replace the optical disk drive on it.
  • Nintendo Switch. Works.

More Archimedes work

The purple is nail polish to protect traces I have cleaned. The green stuff around the RAM is… not good.

So I have been mostly busy getting ready for SwanCon, but I have managed to squeeze some Archimedes work in.

Firstly I attended a meetup of the local Amiga Users Group, which was awesome fun, and while there talked to a couple of other Archimedes collectors.

One individual, Steve, offered for me to drop over and we could work on it together. He lived close by so it was very convenient. (I also admired his extensive collection of retro computers, as well as his Ian Gibson artwork)

Pretty quickly we were able to determine that while it was booting, and getting past POST, it wasn’t as simple as “pressing DEL on the keyboard” alas.

Current working theory is that there’s a dead trace on the board around the RAM somewhere. I’ll have to bust open the logic probe and start tracing around the area to see if I can see what is dead. If it’s a RAM chip, I have replacements on the way. Alternatively it may be the CMOS, and I have spares of that coming too.

One good thing was that Steve and I were able to test my home made Keyboard connector with one of his Archimedes and it works fine. As I track down issues, I know I can, at least, rely on my keyboard and mouse.

Thanks Steve, for all your help!

I’ve been working on the Archimedes

So for the last week I’ve mostly been concentrating on something else but I have spent some time on the new Archimedes. It’s an Archimedes 440, one of the original family, but it has some upgrades installed. Most noticable is the CPU has been upgraded to an ARM 3 processor, and the OS ROMs had been upgraded to RISC-OS 3 as well.

First steps first, I needed to inspect what I had, and let me tell you, this system has seen some horrors.
Firstly, one of the daughterboards (Lovingly called “Podules”) had a Varta battery on it, which had reached “End of Life” and had dumped it’s gust all over the Podule. It’s a writeoff, but thankfully neither hugely important, nor significant. It also doesn’t appear to have got onto the motherboard, so that’s a plus.
Secondly, the batteries for the main board (which were off to one side) were standard alkalines and had, at one point, rotted and split. The case has sustained extensive damage, but thankfully, so far, it’s been surface damage I’ve been able to treat with vinegar, followed by distilled water, followed by isopropyl alcohol.

There’s also some damage to the main board and this is where I have been concentrating my efforts, so far. There were some tracks on the top that looked “dodgy”, eg attacked by acid. I have cleaned off any discoloured tracks back to copper, cleaned, checked for continuity and covered with “lacquer” (Eg nail polish) to stop further oxidation.

There is also extensive discolouring of the solder on the underside of the RAM are of the board. I tried to reflow it a bit but it’s quite stubborn.

At this point I decided I needed to “bite the bullet” and plug it in and turn it on. I had already stripped it down to clean and desolder, plus I had tested voltages coming out of the PSU.
I was greeted with a red screen. According to the super helpful people over on StarDot, this is actually a good sign! It means the CPU is booting. Next step was to plug the floppy drive in and see what happens. Oddly I got nothing. Further investigation showed a PSU with a low 12v line. This usually means a short somewhere. StarDot to the rescue and I carefully snipped out one of the capacitors (C37) which is apparently well known for going open circuit. The system can run without one smoothing capacitor for quite some time. Long term it’ll need a replacement.

So now I had a system that would start to boot then stop. The Archimedes has a very clever system of self diagnostics where it flashes the floppy light in a series of short and long flashes in sets of four. You can then feed these into a special web page that decodes the error.

As I wasn’t getting a full set of codes, I needed to do more work on the system. I cleaned contacts on the bottom of the RAM and cleaned up connectors on the CPU board and finally got it booting long enough to display a series of flashes.
They were:

βˆ™βˆ™βˆ™βˆ™
βˆ™βˆ™βˆ™βˆ™
βˆ™βˆ™βˆ™βˆ™
βˆ™βˆ™-βˆ™
βˆ™βˆ™βˆ™βˆ™
βˆ™βˆ™βˆ™-
βˆ™βˆ™βˆ™βˆ™
βˆ™βˆ™βˆ™-

Which, plugging into the POST error calculator gave me:
RAM control line failure
CMOS RAM checksum error
Self-test due to power-on
So we’re getting somewhere!

At this point I attempted to build a keyboard adapter that’ll allow me to plug in a PS/2 keyboard and mouse so I can at least get the past the CMOS error. It wasn’t too hard, and was based on a commonly available PIC processor so I had that built in a day.

I reassembled everything and tried it again and…

Nothing. Not even the red screen.

At this point I’m stumped. Something else has failed and it’s not even getting to POST. I’ll tackle the corrosion some more on the bottom of the RAM and see if I can get further but maybe I have killed it somehow?

The hardest thing is I don’t have anyone else in the state that can assist. These are rare systems and without a second system, I don’t even know if my keyboard adapter is working or not…

All in all, a bit of a frustrating outcome, but all part of the hobby I guess.

If anyone needs an Archimedes 440 Schematic…

Hi All,
The schematic I recently downloaded from the StarDot mirror of BBC Docs was split into two pages, which made reading somewhat challenging. I’ve combined the two pages, having deskewed and scaled the two halves to match.

EDIT: This is only Page 2 of the Schematic. Looking for Page 1.

EDIT 2: Much better ones can be found here. Thanks to the StarDot team for finding these for me.

What a difference a week makes

Foreshadowing

So on Monday night (after my last post no less) I was feeling enthusiastic, so I stripped down the Mac and gutted out the PSU.
I then removed the switch.
Let me tell you that it’s not as easy as I make it sound with such a simple statement.

IEC at the top, in situ. Below is the switch. See that goop on the switch? That’s not happy-making goop.

Firstly to get to the switch you need to remove the IEC socket, which is soldered into place, and has a weird resistor and capacitor combo soldered across the mains. I had to desolder the wires and loosen a lot of the solder on the capacitor, just to be able to bend everything enough out of the way that I could remove it.

Ugh! This thing!

Next, the switch itself was held in place with this heavy solid glue. I thought it was epoxy, at first, but it melted a tiny bit when I touched the soldering iron to it. I was able to soften it enough to remove by hitting it with some hot air for a few seconds. I was then able to pry off the glue and carefully pop out the switch. It was an extremely tight fit.

Once the switch was out, I could disconnect the connectors for the mains. That freed it up. Going on some advice from the Aussie Apple II users group, I opened up the switch by poking “something” (in this case the tip of some needle nosed pliers) down into the hinge section of the switch case, allowing me to pop open the switch and…

Eww.
More Eww

“Yep. There’s your problem”.

Thankfully Danny on the forum had already tracked down a replacement switch, which I have ordered, which should be here next week.

Meanwhile Greg (who has kindly donated many Apple things to me) contacted me to offer an authentic Apple IIgs keyboard he’d found in his collection. How could I say no?
I did offer him an Atari ST in return but he declined. He did, however, mention an interest in a Commodore 64, and considering his huge generosity in the past, I tried to return a part of the favour by swapping the keyboard for a refurbished C64c, joystick, multi-game cartridge and one of my scratch built c64 power supplies, as well as a cable. Hopefully this will bring him as much joy as his donations have brought me. Thanks Greg!

Keyboard for the Apple IIgs

But wait, there’s more! On the same day as I picked up the keyboard and dropped off the C64, a package all the way from Poland arrived. Aww yiss! It’s my next upgrade, the DDI5 for my Amstrad CPC 464.

So much potential!

This bad boy gives me a floppy drive emulator, similar to a Gotek, a second Floppy Drive connector and finally an additional 512k of RAM.

I had some initial problems, but, as I was able to quickly determine, this was simply because the connector was filthy. I ended up having to disassemble the system, clean everything with an antistatic brush, then polish the connectors with a sand eraser.

After that it stably booted and I was able to work out almost enough to start playing some classic CPC disk games. One demo I wanted to try wouldn’t actually work, and chatting on the Noel’s Retrolab Discord, Noel himself pointed out I was using the wrong command πŸ™‚

(For anyone following in my footsteps, the correct command to load the demo was
RUN”DISC
not
LOAD”DISC
)

As part of that discussion I got to trial his new CPC Diagnostics software, which demonstrated that, yes, my CPC now had 512KB. Awesome!

512KB is all that anyone should need, amirite?

Finally, yesterday, just before I was due to start my holidays, my newest Unicorn arrived! It was an Acorn Archimedes 440/1

So much potential. If only I can organise a Keyboard / Mouse.

As yet it’s almost completely untested as I simply haven’t had a chance to plug it in. I also need to organise a keyboard and mouse for it, as well as some sort of video solution. 15KHz monitor to the rescue!

More to follow, as I explore deeper.