Another one lurches to life

Issue 2 apparently

I have got the Acorn Electron working!

I’m actually quite proud of this one. My diagnostic was that the fourth RAM chip was dead and I was spot on first go.

I’d ordered the RAM from China as it’s so hard to source this stuff locally. While waiting for it to arrive, I realised I’d ordered the wrong type! (I’d ordered 4116, AKA 16k x 1 bit instead of 4164, AKA 64k x 1 bit). I quickly placed an order for the right type, and despite a 2 week gap in my orders, the correct RAM arrived first. (I can still use the 4116 in my Apple II systems so it’s not a loss)

Just felt we needed another picture of the Electron.

When I got home tonight, I grabbed out the desoldering station, the soldering station, my home made extraction fan, some fresh solder and the RAM chips and got right down to it.

My process for desoldering is as follows:

  1. For normal desoldering, set the desoldering gun to about 380℃. I might seit a bit hotter for lead free.
  2. Mark on the underside which chip you need to desolder. Sanity check this. I have learned this from cruel experience.
  3. Wet the pins with the GOOD flux. I save the good stuff for desoldering and surface mount work.
  4. Add fresh solder to the pins. This helps break down the existing solder.
  5. Clean the desoldering gun between every 4 pins.
  6. Place the gun on a pin, then gently wiggle the tip back and forth until you can feel the pin moving. Then pull the trigger and keep wiggling. It should make a noise like a 6 year old with a straw and the last teaspoon of thickshake.
  7. Once all the pins are desoldered, get a fine screwdriver (I use a Jeweller’s screwdriver) to wiggle each pin. Each pin should move freely, or with no effort, it should ping free. Don’t force it! If you have to, add more solder to that pin and repeat step 6.
  8. Once all pins are free, gently try and remove the chip. I usually try fingers, and if that doesn’t work, I slide a thin screwdriver under one end of the chip and see if I can determine whether it’s just held in with friction or if there’s a stuck pin. If it’s a stuck pin, back to adding solder and more suction. Some pins (especially power planes like the ground or 5v pins) may need a bit of additional heat from the top side. Take it gently! We don’t want to lift pads 🙂

This methodology works well for me. I didn’t develop it myself, it’s the result of watching a lot of YouTube people, most notably Jan Beta, Noel and Voultar, plus feedback in various forums.

Once I had it desoldered, I reached for the sockets, only to discover I’d grabbed 18 pin not 16 pin sockets. Oh well. A quick trip to Jaycar was in order. (Hi Alice!)

Returning victorious with a few bucks worth of turned sockets in my hand, I soldered one in and cleaned off the excess flux.
(I know it’s odd having techniques for something as simple as cleaning flux, but I have developed one. First liberally douse the area in 99% isopropyl alcohol, scrub with a toothbrush, cover with a piece of rag, scrub through the rag with the toothbrush, repeat until clean)

I popped in the chip after carefully bending the legs to the right angle and turned it on and…

Aww yiss!

We have a BASIC prompt!

IC7 on the end is the one I replaced. Nice view of the ULA there too.

Now I had it all working, I reinserted all the screws and turned my attention to the tape deck. The connector that plugs into the Electron had unfortunately split due to old age, which meant it wouldn’t go into the socket.
This I fixed permanently by removing both halves of the metal shell of the connector itself, sliding on a piece of heatshrink material, returning the metal pieces, sliding the heatshrink over the metal shell and then shrinking it with my heat gun. They’re held in nice and tightly and the original plastic connector can be replaced without risk of further splitting.

Ready to test

After that it was a simple job to plug the cable into the tape deck, run the magic command to load the tape (CHAIN””) and press play. A few seconds later the game was loading and away we went. So excited!

Loading…

So what next for this system? Well, I might make an upgraded tape deck cable for it. My tape deck supports motor control, so I may as well add it to the cable I have. Further down the track I’ll probably buy an ElkSD64, which adds a virtual floppy disk and an extra 32K of RAM to this unit. It would make a nifty little games machine at that point.

We’re gonna need a bigger boat

Sweet!

So after the teaser last week, I was really happy when a donor who wishes to remain anonymous (Thank you! You know who you are.) sent me across another system for my collection. This one is a real doozy!

Ain’t she purty?

This is a Commodore PET model 4032. The evolution of the very first “real” computer produced by Commodore, and a direct descendant of the PET 2001, the first announced Personal Computer and a member of the “Trinity“.

This model comes with a whopping 32K of RAM, a 40 column display and a full keyboard plus numeric display. It comes with both an internal AND external tape “datasette” port as well as IEE488 compatible drive connectors.

They don’t build them like this any more.

Speaking of that, it came with a 2031 Floppy Disk Drive as well! I don’t have the special cable to go from the Commodore to the FDD, so I might have to make one up somewhere down the track. Or buy one of these.

I have not yet powered this on, simply because there’s so much to do before I can turn it on.

That post to hold up the lid is integrated! “Under the bonnet, son!”
  • The board will need a thorough clean and all the chips reseated. It’s filthy in there.
  • The PSU will need investigating to make sure the transformer is fine, the diodes are OK and the capacitors are at least somewhat in spec.
  • No idea where to start with the CRT. I’ll do a visual inspection at least.
There’s a computer under there.

Other than that, it looks to be in excellent shape. I’m really looking forward to getting this baby going, if I can. While mostly targeted towards business apps, there’s still games being produced for them today.

Quick Updates

I have one of the Microbees booting, having made a quick cable to supply power and video. In the end, I needed to reseat the top board and remove the corroded battery, and that was it!

Yay!
It LIVES! Later I put the cover back on.

Back on the 11th,I bumped my Atari STᴱ, it slid off the shelf and fell less than half its own length. Unfortunately the old brittle plastic has taken on the same material characteristics of enemy cars in the Fast and Furious movies, and promptly exploded! Seriously! it went into DOZENS of bits. I was still finding bits today.

Both upper and lower shell shattered.
This wasn’t even all the shards. I found a big chunk days later, and there were small enough pieces I didn’t even try to pick them up.
These just sheared right off.
This split as well.

I’ve patched it all up with plastic glue but this is no longer a “Pristine” system, alas.

I also have another system theoretically coming this week. I’ll post when / if I get it. I have learned to never trust I’ll get something until it arrives.

The New Haul

So that moratorium on buying new Computers? Yeah that’s totally gone. Look what I got!

Microbeeeeeees!

So I got an incredibly kind offer of a Microbee, with box, no less, and two more “spare parts” systems that were nearly complete.

The Microbee is another Z80 based system. Later models ran CP/M with disk drives but these are from earlier series systems. The system is built around two boards. The lower board has the CPU, video chip and I/O. The upper board has the RAM. Interestingly, in this case that consists of 16k or 32k of SRAM. Yes, SRAM, not DRAM. There’s also a monster Capacitor on board, so it can be turned off for “some time” and not lose the contents of the SRAM. An interesting design. EDIT: This is incorrect. That’s just for smoothing the power supply. There’s a battery (As I found when I opened the sealed unit) that backs up the SRAM.

There’s a key cable I’ll need to make for these that is a DIN 5 on one end and is cassette in and out on the other plus power plus Composite on one cable! Should be fairly easy to make up so I’ll probably be visiting my local Jaycar this weekend.

The main system
Count those 2k SRAM chips!
This is a 16k model

EDIT: I have a working unit!

I traded a system

Three guesses what this is from?

So while I wait for RAM for the Acorn Electron, I thought I’d see if anyone wanted to trade for some of my “spare” systems. I had an extra Atari STᴇ that I had already upgraded to the maximum 4MB of RAM, so I posted on one of my forums if anyone had a spare Amiga they wanted to swap for it.

One of the forum-goers was amenable and offered to swap an Amiga 600 for it. I readily agreed. A day later we had arranged the swap and I now own an Amiga 600.

I like this system for many reasons. Firstly, it’s pretty close to a “perfect” OCS/ECS Amiga, which gives it plenty of compatibility. Secondly, it’s VERY compact. While not having a numeric keypad can be seen as a limitation, the A600 is short enough to fit away where longer systems like the A500 couldn’t. (I’m currently working out if I can build some custom shelving for the longer systems like the 464 or the other STs). Finally, it’s quite a versatile system, capable of taking a HDD, extra “chip” RAM and even PCMCIA devices. Maybe I’ll finally test out that network card I have. 🙂

At the moment, it boots and waits for a disk that I can’t give it. I tried installing a hard disk, but had problems finding one small enough to actually work, without having to upgrade the Kickstart in it. While, down the track I am contemplating a Kickstart Switcher, I don’t have one right now. (I’m contemplating using a 27C160 EPROM, which is FOUR times the size of the normal ROM, and then putting on 3 different Kickstart images, plus a Diagnostics ROM all on the single chip)

Shortly after this, the RCD tripped.

I’ve ordered an adapter to allow me to install a Compact Flash card in instead of the HDD, and I have a suitably sized CF Card I can use.

I’ll replace the Floppy with a Gotek as soon as I order some more. That’ll have to wait for the tax return as that will involve ordering 5 drives, 5 OLEDs, 5 rotary encoders and 7 ultra small form factor USB sticks. That’s a big whack to get in one go.

I have also swapped out most of the yellowed keys for less yellowed keys, as the kind swapper had almost a full set of spare keys. I will, however, need to fake up a stabilising bar out of something suitable as none came with it.

This is an amalgam of a US Keyboard and a UK Keyboard. I’ll live.

Finally, while it supplies good voltages, the PSU currently trips the RCD occasionally, so I’ll want to replace that too. I plan to upgrade it with a MeanWell in the next few months.

I tested the voltages before I used the PSU. The cables and shell are good, and a nice Meanwell Switchmode only will set me back $50.

Oh and there’s potentially a very exciting system coming in the next few weeks. If it arrives I will be extremely happy.

The newest member of my Retro Family

So on Thursday, after receiving a very kind offer, I drove out and collected another system for my collection. It’s another Acorn, which means I now have three different Acorn systems.

Meet the Acorn Electron.

What a cute little Electron!

It was Acorn’s attempt to produce a “price reduced” version of then hugely successful “BBC Micro” family of computers. Much of the logic from the BBC has been reduced to a single integrated chip, the ULA. Unfortunately for Acorn, the ULA was delayed, meaning they missed a significant holiday season, and ended up late to the market.

Nevertheless, it’s an interesting creature, and this particular one came with the tape drive, all the cables and even a bunch of books, magazines, and even an example of an assignment that the previous owner had submitted as part of his studies. (He asked if I wanted it and I said “Yes!”. I often find these pieces of ephemera fascinating insights into the real world uses these systems.)

Having got it home and gone through all the bits and pieces, I started investigating the system. First up was some pre-flight checks. The PSU is an external “wall wart” unit with UK prongs. Luckily I had an adapter I’d purchased to go with my BBC Master. I cleaned the prongs and then carefully measured the voltages and got a nice steady 19V AC out of it, which is what I was expecting. I then found a composite cable and plugged everything together.

Unfortunately, on bootup, I was presented with slightly corrupted blocks, rather than characters. I tried both the RGB signal and the straight composite.

That’s not right.

A bit of Googling later showed no results, but I had enough experience with systems to know it’d be most likely one of three things. Clearly the CPU was running, otherwise the blocks would not be there at all. This means it’s most likely to be (in order of likeliness):

  1. A dirty /damaged ULA socket. The sockets for the ULA are rather unusual. The ULA is on a bonded ceramic carrier with many contacts exposed around the edge. The socket consists of a series of spring loaded pins that reach up and press against the matching contact on the ULA. Unfortunately in harsh environments, both the pins and the ULA contacts can oxidise and need cleaning.
  2. Bad RAM. RAM of systems of this age is notorious. This system uses the same 4164 RAM as the C64C, and I’ve had to replace quite a lot of that in my time.
  3. Bad ULA. The ULA itself may have failed. I was hoping it wasn’t this one, as this is a relatively “unobtanium” chip. Thankfully it’s also a fairly rare failure mode.

I started tackling the potential issues, one by one.

Guts!

Starting with the bad or dirty ULA, I popped open the system, carefully removed the clip that holds the ULA in place, and checked the pins and contacts. Both looked fine, but I carefully cleaned the contacts anyway, with an ink eraser, and a tiny amount of Deoxit.

Socket. So many pins!
The underside of the ULA. You can see where the pins dig into the gold contacts.

Unsurprisingly, it didn’t fix things. Seeing how clean it was, I didn’t expect this to be the fix. Oddly the only dirty component in the system was the keyboard connector, which showed some strange white corrosion. I removed this with some IPA.

What IS that stuff?

Next I looked at the RAM. I ordered some 4164 RAM chips, as I couldn’t find the 1 or 2 ones that I had left over from C64s. Initially I thought I was going to have to wait for RAM to come, but I thought about how the RAM worked and decided to just see if I could see any activity on the Data line on the RAM.

I dragged out my BitScope Micro, and after some false starts, got it hooked up to the Electron.

Checking the first RAM chip gave me what looked like regular data at about the right voltage. I moved onto the next RAM chip and the third RAM chip with identical output, However, when I got to the fourth (and final) RAM chip, I noticed an immediate difference.
There was simply no data coming from that last chip.

I’ll wait for the RAM to come, get a socket and we’ll see if replacing that RAM chip brings the Electron to life. If that does fix it, I’ll have to get some shots of some games on the system. Down the track I want to see if I can get a disk drive / joystick port expansion for the system.

Quick Atari 800 paddle build

So I survived running a convention, and wanted to ease back into doing some retro computing stuff. One of the projects that came up as a possibility was a pair of Atari Paddle controllers. I already have paddles for the C64, but they use different variable resistors, and so are incompatible.

(As an aside, while thinking about this problem, I mentally reviewed doing the project with a digital encoder, a digital potentiometer and a Pro Mini, as I could build a universal adapter for both c64 and Atari, but decided that’s a project for another day. In the middle of contemplation I found myself waking up at 3am and finding myself thinking “I wonder if I could design a digital potentiometer? Turns out I could indeed design one.)

Anyway, I already had some nice spinner tops left over, so it was going to be a quick trip down to my local electronics shop to pick up some bits and pieces. There were some out of stock so I ended up doing some substitutions at the last minute, but here’s what I got:

Originally I’d planned to terminate everything to a solder DE9 female and hide all the “gubbins” in the shell for the connector. Unfortunately they were out, this the change of plan.

I measured and drilled the jiffy boxes to make sure they’d be vaguely comfortable in hand. (I then had to revise as I wanted a push button where the box had a support, so I had to move the buttons down a bit)

I mounted the potentiometers and buttons into the box, cutting off the shaft of the potentiometer to the correct length with a hacksaw. This is easiest to do once everything is mounted.

I cut the cable into two lengths and fed it through into the jiffy box, stripped the end and soldered it onto the potentiometer and the fire button, making sure to record the colour codes of what wire was connected to what component. I made sure both matched, to make construction easier.

Bonus cable tie was in the wrong place.

I the cable tied the cable from the inside of the jiffy box, and added some heatshrink to the outside (I use two layers) to anchor the cable in place. 4 screws in each box secured the base, and then I used an allen key to tighten the spinner knobs to the potentiometer shafts.

Having finished the controllers, I moved onto the rest of the design.

I crimped the IDC cable to the IDC DE9 using my desk vice. I then stripped and crimped on 6 Dupont female crimps. These were so I could easily change any wires if I mucked something up. I had used 8 strand cable left over from another project so I just trimmed the connectors I didn’t need.

Next I got the veroboard (A scrap left over from another project) and soldered in all the sockets and pins. this was a straight through arrangement with 1 pin connected to 2 sockets. It just made it easier for the two connections that needed to be doubled up. Past me would have tried something ugly like crimping two wires onto one Dupont connector, but I have learned my lesson. I will, however, need to buy a LOT more female Dupont crimps in the not too distant future.

Next up was crimping on the Dupont male crimps to the wires from the controllers. At this point I put the female crimps in the 6 x 1 shell and attached it to the vero by the pin headers. I then worked out which wires needed to go to which connection and built up the 6 x 2 shell and male Dupont crimps until I had a suitable connector to drop in the socket at the other end of the strip of vero.

I took time at this point to make sure all the pins went to the correct place on the DE9. I have been foiled in the past by the order the pins come out on IDC connectors so I took it slowly, knowing that if I had to, I could always rearrange the Dupont connector order. They’re quite mechanically strong, but you can pop them out with the aid of a pin.

Dupont connectors FTW!

Once everything was checked I tested on the actual Atari 800xl itself, and it worked fine! After that it was a simple matter of closing up the junction box over the 3 cables and sealing it with a cable tie. A final change was to gently bend back the “ears” on the DE9 to make a better fit.

It took about 3½ hours all told, and that was not pushing myself at all.

Glamour shot.

What next?

While I wait for a bit more financial liquidity before I purchase some more bits and pieces, I’ve been contemplating what to do next. I’m in a strange place where pretty much all my systems work, one way or another. The Wizzard may need a replacement controller, but that doesn’t mean the main unit doesn’t actually work. It works fine. The Amiga may need me to finally get off my butt and laser cut the case, but it works fine. The Archimedes? Works. The Mac? Works.

Most of my systems are even mostly upgraded. I mean, I still need a bit here and there and I need about 5 Gotek units so everything has an actual Floppy Disk Drive and that means $$$ so that is on hold for now.

My next immediate repair purchase will be in a few days I’ll send some money so that I can get a new PSU (And spare CRT Tube) for my SX 64. That will be a nice unit to have working again, especially as this one is in excellent condition externally.

I’ll probably build a set of paddles for the Atari 800. Unfortunately Atari and Commodore paddles are ever so slightly different, which means I’ll have two sets of paddles. That job is really an easy afternoon interlude, rather than a full blown project.

I want to build an ACSI2STM when I get a chance. I’ve laid out a PCB but it’ll need ordering AND testing. I’m cheating by cutting down a DB25 to DB19 to make it fit the Atari.

As for new systems, well I’m still keeping my eyes out for either a reissue or second hand Microbee at a reasonable price, but I’ve not located one yet. One can hope eternal. I have seen someone trying to flog off 3 for $1300 AUD in an untested state. That’s just a little too rich for my liking.

Archimedes Addendum

Foreshadowing

In the last post, I mentioned that the only thing left to do was to make up a cable and I’d be done with the Archimedes.

Well, that turned out to be quite the project, didn’t it?

So the point of the cable is twofold. Firstly, it physically connects everything together and secondly it changes the drive number on the second drive, as I’d been unable to find any obvious jumpers to change the drive letter.

I had some lengths of ribbon cable lying around so I stripped out a length, and pared it down to 34 conductors. I used a permanent marker to mark one side as “pin 1” for some of the length and the opposite side as “pin 1” for the rest. (Archimedes floppy pin 1 is opposite to Gotek pin 1, for some strange reason)

I crimped on 2 of the 3 IDC connectors, making sure to get the connectors / connector notch on the right side, as well as having them the “correct” side of the cable to make it easier to insert. (There’s a bit of a trick here, as the strain relief actually flips the cable so you have to factor that in.

I then carefully separated the strands every 4 wires. for the length that was to go to the Gotek. This guarantees ground cables will stay together with data lines. I ended up with 2 sets of 5 in the middle, but I knew that was going to happen.
This was all done to make the floppy cable much more flexible.

Finally I trimmed about a 5mm section out of wire 1 on the Gotek side (wire 34 on the Archimedes side) as the Gotek doesn’t like a signal that gets sent down that wire and can burn the controller. Let’s not burn the controller. Honestly, I have read so many forum posts and the like getting to here, I don’t even remember where I saw that.

Now onto the other side of the cable. Following this guide (Part of a two part article which appears to be the only article out there on adding second drives), I carefully split the cable between wire 9 and 10, and 12 and 13 and added a twist and clamped on the final IDC connector. We’re done! (Or are we?)

I inspected my work, triple checked where I’d put the twist and mounted it in the Archimedes. The connector for the motherboard was the central one to make routing much, much easier. Everything looked neat and proper so I gingerly plugged one end into the Gotek and fired ‘er up. Well so far, so good. I could read and write to the Gotek OK.

Unplugging the Gotek and plugging in the FDD, nothing caught fire, which was a good sign. I went into the Configure app and added an additional drive. I inserted the Floppy and… No.

First up I got a Drive 10 Error and then “Drive Empty”. Maybe it’s that the other end wasn’t terminated in a device? Nope. Plug in the Gotek and neither device works.

Hmmm.

I check my guides. I check my cabling. I check my logic. I check my software settings. Nothing obvious I can see.

OK StarDot, my new friend. Can you help me?

Having posted my issue, someone else reports they weren’t able to get things working quite right yet either, using the guide I was working with so I start looking for another guide. I stumble onto this article (by searching for slightly different search terms) which has a reference to the actual model number of the internal FDD. And that gets me to a drive manual. Guess what? I don’t need to put the twist in the cable, as this model has a switch cunningly mounted on the side that sets the drive number!

It can’t be that easy, can it? I set the jumper on the floppy, (This entails removing the drive from the computer AND the mounting bracket) connect a straight through cable and… check! it’s working on floppy disk as Drive 1.

Oh gods! I pull the cable out, break off the strain relief bar, remove the end of the IDC connector with a pin, un-twist the cable, reclamp it and reattach it.

Oddly initially it works once and then starts doing “Drive Empty” errors, but then, as it’s now nearly 10pm, I screw everything back in and tighten everything, it just works perfectly. Huh! I have a two drive setup. Sweet!

Elite is coming off a floppy disk. PacMania is coming off an ADF via the Gotek.

At this point, for reasons I don’t quite understand, you need to access the Gotek before you access the FDD. Go figure?