Continuing Adventures in RetroComputing (Repost)

(Originally posted on LinkedIn May 18th, 2020)

Based on a picture from WikiMedia: https://commons.wikimedia.org/wiki/File:Apple_II_Plus_Inside_Microsoft_80_Column_Card_Closeup.JPG

As I have posted here before, my current hobby is fixing up old computers. Some of this involves working with components and tools not easily available at your local walk-in electronics store. Some of these can be covered by the “usual suspects” such as RS Components and Element 14, (My preferred suppliers) but some of these can only be purchased from obscure suppliers, often in China.

As you can imagine, recent global events have slowed the supply chain down dramatically, but things are finally starting to trickle through.

As a result, I was finally able to tackle my Apple II+ recently, having finally received my 4116 DRAM chips. The Apple II used 3 banks of 8 of these to generate the first 48KB of memory, with an additional bank of 8 on a “Language Card” (So called because they were needed to run additional languages such as PASCAL) to bring it up to a compliment of 64KB.

The whole point of this was to get the whole shebang ready to run a serial link back to a PC so I can copy across floppy disk images.

Unfortunately I still have an intermittent issue with memory corruption, and it’s really annoying. I am in a “chicken and egg” situation insomuch that, if I had a working system, I could get diagnostic disks made which would help me to resolve the issue, but as my system doesn’t work, I can’t get the disks, which means I can’t find the problem…

(Insert joke about holes in bitbuckets)

I’m not giving up, however. My current plan is to pull it all out of the case and check key busses with an oscilloscope. See if I can isolate out where things are “going bad. I’m also tempted to get a EPROM programmer, as many of them will also test 74 series logic. I may also see if someone on the various Apple forums are willing to burn me a couple of Diagnostics disks.

If that fails, I might just have to buy another Apple II to use to help me fix this one!

Here’s a list of what’s already been found and fixed:

1. Many chips with significant oxidation on the legs. They looked like they had been steeped in strong tea with a browny black patina. Cleaned with a sand eraser and their sockets cleaned with electronic contact cleaner. This improved things a lot, and got me to the point where it’s semi-stable.
2. Custom cable constructed to connect from the Floppy controller to the Floppy drive. I had to customise both the cable and a connector. Apple used a 19(!) pin D connector, which I worked around by getting a 25 pin connector and pulling 6 pins out with pliers.
3. On the Language card, replaced ALL the 74 series logic chips with new ones. Also replaced the ribbon connector between the card and the motherboard. This was, once again, a custom made part.
4. Identified and replaced all 4116 memory chips. I believe all the ones I was using are good components as I “swap tested” them, but it was cheap to swap out all of them, so now they’re identical. I did find several bad ones.

Retrocomputing News (Repost)

(Originally posted on LinkedIn Feb. 6th, 2020)

(Image from Wikimedia, used under a CC license – https://commons.wikimedia.org/wiki/File:Acorn_BBC_Master_Series.jpg)

Well, I continue to collect old computers and consoles. It’s a fun hobby and exercises skills I don’t get to use at work as much any more.

The pleasure of starting with a beat up old system and getting it working properly is a real buzz, and lets me practice both practical skills (Such as soldering) and analytical skills (Such as fault finding).

Currently the collection is getting along nicely.

I have the following computers:

1. A Commodore Vic 20 (5k RAM, 1MHz 6502)
2. A Sinclair Spectrum (48k RAM, 4MHz Z80)
3. An Apple II europlus (48k upgraded to 64k, 1MHz 6502) – I have replacement RAM on order for this beastie. Until then it tends to “barf” whenever I try to load a disk needing more than 32k.
4. 4 x Commodore 64 (64k RAM, 1MHz 6502) + an assortment of peripherals, such as disk drives, printers and such
5. A Commodore 128D (128k RAM, 2MHz 8502, 4MHz Z80, Integrated FDD) – Sadly this machine needs more work as the power supply trips when I turn it on
6. A BBC Master System (128k RAM, 2MHz 65SC12) – This is so new, it’s still on it’s way to me
7. An Atari 1040 STfm (1M RAM, 7MHz 68000) – Upgraded with a Gotek Floppy disk emulator, a nifty gadget that allows you to use a USB stick to pretend to be a floppy drive.
8. A Commodore Amiga 1200 (2M RAM, 14MHz 68EC020, AGA Graphics) – This one is waiting for me to get a chance to laser cut the case. I have extensively customised this one, as it had been “hacked” before I got it. This taught me a lot about circuit board design as I designed and ordered my first commercially manufactured PCBs for this system. This also has a Gotek.

I am also building up some “classic” consoles too:

1. 2 x Nintendo Entertainment Systems – Neither work currently but I know why. I just need to actually buy the part to fix it.
2. A Sega Megadrive – I’ve been trying to get decent RGB Video out on this for MONTHS, but it’s manage to elude me so far. I’m not giving up yet though. A new week, a new version of an RGB cable.
3. A Commodore Amiga CD32 – Oddly this one can be very easily upgraded to be a full blown computer comparable to the Amiga 1200 above. So far I’ve resisted the urge.
4. A Sony Playstation 2 “Phat” with an added hard disk and network card.
5. An original XBox. (Dear Microsoft, calling your THIRD XBox console the “XBox One” was a dick move. Seriously. Do you know how hard it makes getting info about the original?)
6. 2 x Nintendo 64. Mmm. Tetrisphere was such a masterpiece.
7. A Nintendo Wii. The optical drive has died so I use an external HDD instead. Much more convenient.
8. An XBox 360. Eh. It was cheap.
9. A Playstation 3. I bought this new. It was shiney when I got it. A particularly nasty weekend doing far too much overtime payed for it.
10. A Wii U. Kids got it as a Christmas present, when they were no longer very new. I like Breath of the Wild on it.

I also have a Raspberry Pi setup as an emulator to cover those systems I haven’t yet collected. If you are only casually interested in the old systems, these come highly recommended!

Once I have the Beeb, there’s not too many “must have” systems on my wish list, not counting the occasional “Unicorn” system out there that I’m unlikely to ever get.

I still want to get an 8 Bit Atari, such as the Atari 800XL, and I am actively searching for a Microbee, either in kit form or an original. (These were used in Australian schools in the 80s). I’m also likely to buy a Harlequin 128k kit (Emulating the later Spectrum 2+). Finally once I have all those I’ll probably start looking for an Amstrad CPC 128.

As for consoles, I’d like to add a Sega Dreamcast and a Super NES. However I keep my eyes open for the disturbingly rare Dick Smith Wizzard. (AKA the CreatiVision) The latter is definitely veering towards “Unicorn” status.

Quick retrocomputing update (Repost)

(Originally posted on Dreamwidth Feb. 3rd, 2020)

NES are still cranky.
Apple ][ has RAM on it’s way. It’s on a slow plane from China. I found a small machine-code memory test I could type in but it’s a pain to have to type it in each time so I plan to swap out banks at a time and isolate that way.
I made a ST to VGA cable and it works an absolute treat! So pretty!
I have ordered a BBC Master (the big brother of the BBC Micro), which gives me only two of the major 8 bit families to collect: The Amstrad CPC family and the Atari 800 family.

A boy can dream… 🙂

RetroComputing adventures (Repost)

(Originally posted on Dreamwidth Jan. 8th, 2020)

Oh Hey! It’s been a while.
Just a quick update.
So:
Both my NES are now dead. Doesn’t seem to be the edge connector, although I’ll be buying a new one of those to make sure. I figure I should be able to get one or both working once I have a day to work on them.
I now have a MegaDrive. Still haven’t worked out how to get any decent video out of it. It shouldn’t be this hard! It supports RGB out of the box. I may have to bite the bullet and get an OSSC and a decent SCART lead for it. That does feel like a path that leads only to darkness.
I have an XBox 360. Not a bad bit of kit. Games are cheap.
I have upgraded my PlayStation2 to being a “Phat” and have added in a HDD and a network card. It needs some TLC but is nearly ready to redeploy.
One of the C64s has failed but in good news I’ve located a source of replacement power switches.
I’ve also purchased an Atari 1040STfm. It’s got a Gotek drive in it, so I’ve purchased the “upgrade” components so I can convert it to use a small screen and a rotary dial. They’re on their way.
Finally I have an Apple II europlus. Cranky computer! I’ve done a fair amount of work on it. It works some of the time but not all of the time. It’s quite feature complete, but I’m battling to get the reliability up to the point where I can start actually doing things with it, like, booting off a floppy disk. Unlike most of my systems that support some sort of diagnostics card / board / ROM, this model doesn’t seem to have any of that. I’ll keep working on it. Tempted to trade it up for a later model with better inbuilt stability.

Quick Post: I am feeling rather chuffed with myself. (Repost)

(Originally posted on Dreamwidth Jan. 10th, 2019)

So if you’ve been reading this a while you’ll know I bought 3 dead C64s. I managed to get one working by cleaning the power switch. (Cleaning the switch also got the next two working closer to full completion). The second one I got working by taking the RAM out of the third, which was showing symptoms much worse than the other two.

The third one was just sitting there, taunting me with a black screen and nothing else.

I did some research and it turns out the fault was likely to be one of 3 chips. Two of those chips were pretty reliable and also insanely expensive to replace, so I ordered the third chip (The PLA) on a whim and some new RAM. (Apparently, yes, you can buy new RAM for C64s. Who knew?)

All those parts arrived today.

I then took my “good” C64 (the middle one) and socketed it’s PLA. (I had already socketed the RAM chip). This allowed me to test the new components in a known good machine. The new parts all worked fine.

So I socketed up the third machine and tried the RAM and PLA in there. It worked first time!

So now I have FOUR working Commodore 64s. This is 4 more than I had this time last year 😀

(Big shoutout to Shrydar for allowing me to buy his old parts for an excellent price)

Even More Retro goodness (Repost)

(Originally posted on Dreamwidth Dec. 22nd, 2018)

So the Pi1541 arrived and I am amazed how useful it is. It’s not 100% compatible yet, but gets better every week. I LUFF it.
I’ve built the PSU for the 1541 floppy drive and that drive is currently formatting up disks in the background.
The C128D monitor is fixed, but I need to build a stand for it as otherwise I won’t have any desk at all. I also need to replace the failed switch with a working switch I just found.
I’ll need to order parts for the second 1541 PSU and C64 PSU. I’m really tempted to build a “pure” C64 PSU as per Greisis Workshop
After that it’s probably time to rejoin Artifactory, except for the small issue of their laser cutters being out of action AGAIN.

More retro goodness (Repost)

(Originally posted on Dreamwidth Dec. 7th, 2018)

Well, let’s see. I’m a LOT better at all this stuff. I have the A1200 booting, and more! It has:

• A proper LCD monitor that supports the wonky frequencies the Amiga uses (15KHz vertical refresh).
• An SD to HDD adapter, with an 8GB SD card in there pretending to be a couple of hard disks.
• A keyboard adapter allowing me to use an old PS/2 keyboard with it.
• A mouse adapter that I designed and made that allows me to automagically change to a joystick in the same port.
• A Virtual Floppy drive (Works from USB thumbdrives full of disk images) that I flashed the firmware of and added all the extras such as
  • An OLED screen that shows me which image I’m using.
  • A pizeo speaker that simulates the buzzes and clicks of the original.
  • A rotary selector that makes disk choosing easy.
• A design for a laser cut case to hold it all, only pending the Artifactory fixing their damned lasers again.

I also purchased a batch lot of Commodore stuff and now have:

• A Commodore 64 (More on this later)
• A Vic 20 (With a whole bunch of carts)
• An SX64 with what appears to be a dead PSU
• A Commodore 128D. This is a “Work in Progress” as it has a problem. I’ve recapped it but it fails when I plug the PSU back in. Basically I need to take it to the Artifactory and plug it into the bench PSU.
• 2 Floppy drives, one of which definitely works, one of which needs some more love.
• 2 Printers(!) that I’ll need to gove some love to once I have everything else under control
• A C128 Monitor which has a loud scary crackle.

I had to build a new PSU for the C64 and Vic20 as the “stock” ones are notoriously bad. They have a nasty “fail to high voltage” that’s really efficient at cooking chips. This was an interesting challenge but I got there in the end. I’m always a bit squirrelley around AC voltage. 

I then purchased a job lot of dead Commodore stuff. 3 C64s and another FDD plus a joystick. This was for a fraction of the price I paid for the batch job above, but that was cos it was all failed stuff.

So initially I plugged all three C64s in one by one and documented the faults. Two had a problem where I got monitor sync and nothing else. One had zip. Nada. Nothing.
Doing standard fault finding I found the first two had no DC voltage and the second had no AC voltage. Turns out the switches on C64s have an effective lifespan of about 20 years… These were 1986 models. 
I had to desolder the switches, which turns out to be one of those understatement things like “And then the atomic bomb exploded” as Commodore must have hated their service technicians. There is an RF shield that’s soldered on to the motherboard. I manged to desolder the RF Shield through a combination of my soldering iron on maximum and using a set of dental picks as prys. Once THAT was off my desoldering station made quick work of the switches.
I desoldered, cleaned, greased and assembled and suddenly 2 of the 3 were booting! The third was now getting sync.
Of the two booting ones, one was perfect. It’s now in my stack of “working” gear waiting for a recapping. I’ll probably sell one of the working ones.
The other was showing rainbow garbage, an issue consistent with bad RAM. This led to more purchases.
I next purchased a couple of cartridges (Dead Test, 60 in 1) and some bits and pieces.

My next project was to build a pair of paddles for the C64. Unfortunately I haven’t had a chance to test them yet.

I used the Dead Test to confirm which chips were bad in the dead RAM c64 and I decided to use the OTHER dead c64 as a parts donor (As it was showing fatality on one of the key chips)

I have, however, been unable to desolder the RAM off my sacrifice board! I’ll try again this weekend if I can but it’s more challenging than I would have expected. After half an hour I’ve manged to get ONE of the chips to sit at a jaunty angle and that’s it.

Still to do:

• I need to build a pair of 1541 ii PSUs. I have the parts for one but will need to order more bits.
• I need to recap all of the c64s
• I need to build more PSUs for c64s
• I need to get to the Artifactory and test what’s wrong with the c128D and get it working!
• I need to get my c128D monitor to the guy who has offered to have a look at it.

Stuff “in the mail”

• Utility cart (Including Fastload, Freeze and loads more stuff)
• Pi1541 (This is an awesome doodad you plug into a Raspberry Pi and it emulates a Floppy Drive.

World of Retro (Repost)

(Originally posted on Dreamwidth Jul. 11th, 2018)

What have I been up to? Well, a bit of this and a bit of that. Picked up a new hobby, BTW.

What’s that? You wanna know more about my new hobby? OK.

So after watching many YouTubers playing with classic computers I decided I wanted in. I’d recently acquired an Amiga CD32, which I got recapped (It was all SMT so I wasn’t going to do it I can tell you) so I had a foot in the door. I built a new PSU for it and I had a working console but I wanted MOAR!
At Swancon I asked around and a friend came to the party as she had a few more systems gathering dust. (I won’t name her to respect her privacy) This netted me an N64, a NES and, most interestingly a Sinclair ZX Spectrum.
Meanwhile I ordered an Amiga 1200 off AmiBay in a semi-working state (Don’t ask how much it cost. I’m mostly using it for parts.) which took three months to get here.
I have had some leave recently, so in a flurry I have:
Recapped the NES and the Spectrum
Purchased a new PSU for the Spectrum.
Replaced the cartridge connector on the NES <- At this point it was working.
Converted the Spectrum to use Composite out rather than TV Out. <- At this point the spectrum was booting.

The Spectrum needed much more work.
Although it was booting, the keyboard was unreliable. It was in an aftermarket case which meant I didn’t need to deal with the notorious membrane. This took me ages to fix as it was multiple issues overlapping. Firstly, all the contacts were corroded. This was solved with some contact cleaner, a bamboo chopstick (They make excellent “soft” contact cleaners) and some strips of cardboard. Secondly, some of the wires on the keyboard connectors had poor solder joints. I desoldered / resoldered them and that fixed that. I needed to also trim the edge of one of the connectors to ensure a better electrical connection with the motherboard. Now I could boot and type.
It took me a while to work out exactly HOW to load a game, and I didn’t have a tape deck in a working state. I solved this issue by using my Android phone, a piece of software called “TeeZiX”, and an eeevil custom made cable. Now I could even load games.
This is the point one of the key buttons on the keyboard stopped working. Thankfully I was able to resolve that with some contact cleaner.
I was loading games! I was even playing them! W00t!

My next step is to wait until next month so I can afford to buy another PSU to hack into the Amiga 1200. I think at this point I should be able to get it to boot to the “Insert Disk” screen (I hope). I’m not sure how I’m going to proceed from there to be honest. My big challenge will be getting bootdisks ready to boot the Amiga to the point where I can format and install an OS. The Amiga uses a non-standard floppy disk format (880K) that I may need to build a USB to FDD bridge just so I can write out the disks from images.

So that’s kept me busy.

Oh, and if you happen to have an old C64, C128, or an Amstrad CPC machine you no longer want / love, let me know 🙂

First Post

This is a brand new blogsite. I’ll be bringing content across from other sites as I go forrward.

So what are we doing here? Well, I had content scattered across thing such as e-mails, websites and even LinkedIn. None of it was in one place. This page will consolidate all my musings and experiences with RetroComputing.