I was shocked at what was keeping this Acorn Electron from working (Acorn Electron Repair)
ฝัง
- เผยแพร่เมื่อ 28 พ.ค. 2024
- It's time for an exotic (for me) repair of a very interesting 8-bit computer from the makers of the BBC Micro. This Acorn Electric is dead and let's see if we can bring it back to life!
Part 1: This video!
Part 2: • This Acorn Electron wo...
0:00 Intro
0:52 Unboxing
4:33 Background and details on the Acorn Electron
12:24 New modern power supply
18:25 Troubleshooting and repair
46:27 Converting the Electron to NTSC
-- Links
ATX4VC PSU:
github.com/dekuNukem/ATX4VC
Acorn Electron:
en.wikipedia.org/wiki/Acorn_E...
BBC Micro:
en.wikipedia.org/wiki/BBC_Micro
BBC Literacy Project Archive:
clp.bbcrewind.co.uk/
4corn Acord schemtics and service manuals:
www.4corn.co.uk/articles/diag...
PlayUEF: (for loading projects over tape)
github.com/8bitkick/PlayUEF
Adrian's Digital Basement Merch store:
my-store-c82bd2-2.creator-spr...
Adrian's Digital Basement ][ (Second Channel)
/ @adriansdigitalbasement2
Support the channel on Patreon:
/ adriansdigitalbasement
-- Tools
Deoxit D5:
amzn.to/2VvOKy1
store.caig.com/s.nl/it.A/id.16...
O-Ring Pick Set: (I use these to lift chips off boards)
amzn.to/3a9x54J
Elenco Electronics LP-560 Logic Probe:
amzn.to/2VrT5lW
Hakko FR301 Desoldering Iron:
amzn.to/2ye6xC0
Rigol DS1054Z Four Channel Oscilloscope:
www.rigolna.com/products/digi...
Head Worn Magnifying Goggles / Dual Lens Flip-In Head Magnifier:
amzn.to/3adRbuy
TL866II Plus Chip Tester and EPROM programmer: (The MiniPro)
amzn.to/2wG4tlP
www.aliexpress.com/item/33000...
TS100 Soldering Iron:
amzn.to/2K36dJ5
www.ebay.com/itm/TS100-65W-MI...
EEVBlog 121GW Multimeter:
www.eevblog.com/product/121gw/
DSLogic Basic Logic Analyzer:
amzn.to/2RDSDQw
www.ebay.com/itm/USB-Logic-DS...
Magnetic Screw Holder:
amzn.to/3b8LOhG
www.harborfreight.com/4-inch-...
Universal ZIP sockets: (clones, used on my ZIF-64 test machine)
www.ebay.com/itm/14-16-18-20-...
RetroTink 2X Upconverter: (to hook up something like a C64 to HDMI)
www.retrotink.com/
Plato (Clone) Side Cutters: (order five)
www.ebay.com/itm/1-2-5-10PCS-...
Heat Sinks:
www.aliexpress.com/item/32537...
Little squeezy bottles: (available elsewhere too)
amzn.to/3b8LOOI
--- Links
My GitHub repository:
github.com/misterblack1?tab=r...
Commodore Computer Club / Vancouver, WA - Portland, OR - PDX Commodore Users Group
www.commodorecomputerclub.com/
--- Instructional videos
My video on damage-free chip removal:
• How to remove chips wi...
--- Music
Intro music and other tracks by:
Nathan Divino
@itsnathandivino - วิทยาศาสตร์และเทคโนโลยี
All Acorn 8-bit machines have the ‘Old’ command. Hitting break is a reset and typing OLD or O. will restore the programme.
It’s really useful, as are a lot of BBC Basic’s shorthand commands
Yes, at th-cam.com/video/sukuk-miq4U/w-d-xo.html :
RESTORE is a standard BASIC statement that sets what DATA statement will be used next. (In BBC BASIC, it can be used with no parameter, to choose the first DATA statement.)
Pressing BREAK (or CTRL-BREAK) effectively does NEW (among other things), which sets one byte near the start of the tokenised BASIC program (the 2nd byte to 255), to mark that as the end of the program.
OLD restores this to 0. That byte holds the most significant byte of the line number, so if the first line of the program had a number higher than 255, it would end up being its original number modulo 256. Of course, you can't use OLD to recover a program after entering a line of a new program.
Yep,
O.
L.
for 'OLD LIST' and there's your lost program. Even after a CTRL-BREAK.
One of the best repair videos you’ve ever put out! Thanks Adrian and thanks to the viewer who sent that awesome little machine in!
As the person who sent it in, you’re welcome haha
I love the Electron, I think after the BBC Micro it’s my fav retro computer, as I have a soft spot for technology that’s a bit crap or failed at something but is trying oh so hard to be awesome that I can’t help but love it!
I think it's a shame he's changed out the power supply. It can't be THAT hard to find a 19V transformer.
@@jovetj No AC transformer is required. It'll work just fine from 12 volts DC.
@@ControlledPodIntoTerrain I'm sorry, I believe you missed my point.
@@jovetj I believe you missed mine, which was that the machine doesn't need AC and doesn't even need 19 volts- it will work just fine from 12 volts, and 12 volt power supplies are everywhere. Changing out the power supply was really unnecessary.
You using the Metal Gear Solid guard alert sound when you discovered the ULA was desoldered made my life. I even showed my wife. I have grown up playing the games and love the Metal Gear series to death, so it really was funny and cool to hear it out of nowhere. I can’t wait for part 2, and you’re a gem, Adrian. I’m so happy to be a patron and support you. Your content has really taken an upswing and it has to be that you can finally full time do what you love, and it shows. Love ya, Adrian, keep it up!
yeah that was perfect lol
So that's where that sound is from? Thanks. Now I know. :)
This happens in software sometimes, too. You're trying to diagnose a weird problem, looking all over where the culprit should be, but everything looks fine. You start thinking of complicated, improbable explanations for what's wrong, dejectedly browse around sections of code where the bug can't possibly be, and…there it is! Simple, obvious, just not where you'd think to look.
@@argvminusone Sounds like when I was writing an installer and poked around for three days to find out I was modifying the wrong file.
@@argvminusone Happened to me the other day with, of all things, some 6502 assembly code. While attempting to get reliable data transfer between an Arduino and a homebrew 6502 board, the transfer kept failing. I had the Arduino send a fixed 64-byte string, which the 6502 would then write to SRAM and send back 64 bytes to be printed on the serial monitor. 2 bytes kept getting lost off the end every time I tried. The string I was using was "Let's make sure that history never forgets the name.. Enterprise". I had copy-pasted this Star Trek quote from a website and trimmed some characters off to make it fit in 64 bytes. While testing, the last two letters kept getting cut off. I had spent an entire evening checking everything - the wiring, the assembly code, the Arduino code, the assembly code again, to no avail. As it turns out, that apostrophe in "let's"... was not an apostrophe at all. It was a right single-quote. That stupid thing is a 3-byte unicode sequence. I hadn't noticed until I looked at the raw hex dump. It shows up as a single character in the Arduino IDE and serial monitor.
RESTORE is used with READ and DATA. BBC BASIC had a nice little extra keyword called OLD. It's the opposite of NEW! So after a reset you _might_ be able to get your old program back, but do it first thing. Any other messing about you do is likely to scramble the memory pointers and make the old program irrecoverable.
Great video, Adrian! You can get back your program after hitting BREAK using the OLD command.
I came here to say the same. 👍
I also came here to say the same 😉
Unless someone adds the line ?(TOP-1)=0 as the first line of the program code.
@@crashoverride328 Really ? I have'nt really used mine much. I got the SD card expantion for it and wrote a few BASIC/Machine code progs but got bored and went back to the Spectrum and ZX81. LOL. Great info though.
Also came here to say this
Not sure if anyone else has mentioned it, but the first computer Acorn produced was the Atom, had the BBC not taken up their next machine, the BBC Micro would have been called the Proton, and thus calling this the Electron makes a nice trio of names
Acorn actually produced a few machines before the Atom, the System 1, 2 and 3, which were rack mounted. The Atom was a cut down System 3 and their first home computer system.
@@cshairydude Thanks. I’ve never heard of those three.
Fantastic to see the Electron come up! I’m the one who sent it to you and was so excited for when it would pop up.
As for its story like you asked, unfortunately I don’t have much to go off of. I bought second hand as not working and only did quick checks, like you I did a bunch of initial checks and found it not working despite presumably all voltages and such accounted for. However I didn’t turn over the board to find the obvious issue!
Like I said in my letter I did test keyboard on my working machine, so knew it was completely fine luckily. I also did clean it up cause I didn’t wanna send a gross machine though! Hence the tidiness 😅
Anyways I’m glad it worked in end, can’t wait to see more of it.
Quick edit: also a fun fact, in the time since sending the Electron I actually came out as trans and am actually Diana now! 😅
perhaps you can send some program cassettes to Adrian!
@@boeingav8tr525 I wish! I do have a set of really nice ones in all their originals official Acorn boxes and storage holder thing, but it’s mine 😈
Thank you for sending it to Adrian, where you know it will get the TLC it deserves. Quick question: Could the Acorn run Elite? or did it need the extra RAM of the Beeb?
@@exidy-ytIt has a great version of Elite except fully monochrome, amazing for such a low spec machine
@@exidy-yt yeah I think there’s a Electron specific version you can probably find on that site Adrian used
In the mid-1980s to early 1990s, I wrote software for the BBC and designed hardware for a specific group, the physically disabled people. The BBC was the easiest computer to do this on, and in Belgium these old computers are still used in some locations. It is a wonderful machine that has helped many people. I still have a BBC in my house and would not part with it for the world. Due to being idle, several components needed replacing, but it was wonderful to maintain and repair. There is still a whole group of people working on this day in and day out.
My first ever home computer... Brings back so many memories.
How cool! I am from London and still have a 40 year old Acorn Electron in a drawer with loads of game tapes and a tape player. I was about 6 when my dad bought it and we spent hours typing in printed magazine listings and running them. That influenced my education path into computer science and then software engineering.
Same. I have a crate with about 600 tapes and a few electrons.
I think you're right. The 6502 probably gave up first. Then someone changed it for the wrong version. That lead them to believe the ULA was at fault and started to remove it, damaging a trace in the process, but then gave up and didn't bother to try and re-solder it back. That all makes sense.
That's pretty much what I figured too, I know a fey lazy 'tech' guys like that who give up halfway when a little more poking or re-thinking their approach would save the job.
Acorn fitted the Rockwell R6502A to many Electrons from the factory. Although it's out of spec, it usually works just fine. "Out of spec but seems to work" is a pretty good description of the Electron all round, really. Many of the 6502's pins are directly connected to the edge connector at the back, so it is believable that it could have been damaged by ESD, or just drifted with age, and now no longer works that far out of spec.
Notably, in screen modes 4 through 6, the CPU clock does not stop for 40 microseconds like it does in modes 0 through 3. The Electron powers up in mode 6. So even if the CPU was not capable of surviving a clock stopped for 40 microseconds, it would still work at power up.
@@skonkfactory Thats interesting. Adrian did re-check the 6502 once the ULA was resoldered back in, and it checked out as working as a standard 6502. It just didn't work in the Electron. So it looks like it was out of spec, enough to make it fail in this application. But you're saying it should have still booted?. Thats a mystery.
@@g0bzy The Electron's all sorts of electrically marginal, though the ones with the Synertek gate array (like this one) are much less so than the ones with the Ferranti ULA. It's also possible that the 6502 was slightly damaged and didn't like the 2 MHz cycles that the Electron does when accessing ROM.
For what it's worth, I've tried fitting a (recent- fabbed in 2021) 65c02 to an Electron and it does not like the slow rise time on the clock waveform generated by either the Synertek or Ferranti ULAs. I had to fit some logic to speed up the edge there. Also you need to lift a couple of pins and pull them low since the wdc 65c02 has some extra signals. Once I'd done that it worked like a champ, though!
42:30 *the ZIF VIC-20 board* that voice had me rolling for no reason, it just surprised me.
About the tape connector: I noticed that the manual mentioned that you can plug it straight into a standard tape recorder if it has the (then) standard DIN audio connector. You mentioned that you saw about 2.5V of audio signal, and in that case the problem might be that it is too loud. IIRC the DIN standard specified a line level of 600 mV.
The User Guide suggests "medium volume" on a "domestic cassette recorder" which, given that full line level is about 1v p-p, would imply about that voltage level- a half a volt or so.
my spectrum was the same, too loud and the game wouldnt load
Yay! Pleased to see my BBC Master again! 😍
You’re awesome for sending it in. A piece of computer history this American here is glad to learn more about and very happy it’s in Adrian’s loving hands. Again, you’re a wonder and I hope you have a wonderful Christmas (and Boxing Day), and a happy New Year. You’re very appreciated across the pond. :)
@@TechnicolorMammoth aaah, thanks! I wanted to send the complete machine, monitor and take decks and everything, but it was just not possible (fragile and size). Adrian did a great series on its restoration. I knew he already had a BBC Model B, so the Master 128 was a good candidate.
I worked for a company near Brighton in the UK in the mid 80’s who made ultrasonic wire bonders, we were given Acorn Electron motherboards that had the ULA chip wafer, bonded directly to the PCB without any connections, Acorn wanted to manufacture the motherboards at an even more cost reduced than the version than the one in the video.
The machines we made were used to manually bond each contact on the chip wafer to the PCB, and once proven all was good, the process would have been automated, the completed PCB’s were returned to Acorn, and we never did any more work on the Electron. I think at this point, its days were numbered!
You didn't need to replace the original power supply. You can use any laptop DC supply, 15 to 19 Volts DC on the Electron. The switching supply on the power supply board generates the + and -5V supplys without any need to have an AC input.
Indeed, it wasn't obvious it was switching and the schematics I looked it didn't include the PSU schematic. I just looked at it now and clearly it would have worked just fine. on probably as little as 12v DC as well! No need for 19v even....
@@adriansdigitalbasement I use 12vdc with no issues.
That’s mostly true, but be careful. You can use dc on an ac device, but the amperage and the dc voltage and amperage is probably going to be different that the ac markings. Best to do the math for the device type and power supply components that you have.
@@adriansdigitalbasement Yeah, I can confirm that 12V DC works just fine. I have three electrons and all of them are perfectly happy on that.
@@trssho91 If using a DC supply for something that is generally expecting an AC supply, the FIRST thing to look for is a transformer on the power circuit directly. If you put DC thru a transformer, ALMOST all the times something DRASTIC will happen BAD! DC will typically overheat the windings, but AC will go hot one cycle, and then not on the opposite .
As A brit, I was screaming at the screen when you called it an Acorn Electirc!! lol twice!
Between the BBC Micro, the Electon and the Archimedes, they all put me on a career in IT, Thanks for the memories Adrian.
Ditto - although I started before I got the BBC with an Oric1 before that, a ZX81 before that, and using a Commodore Pet at school as the very first computer I touched and learned on.
But the Acorn machines to me, taught me lessons of how computers should be done “right” where as the others all felt like bodge jobs once I’d experienced the elegance of the OS design that Acorn always had. :)
Same here - I started on a ZX81 but the BBC B got me writing school software for my mum's classroom. I never had an electron but I did get an A3000 which moved me into graphical interfaces.
@@andyjdhurley the built in assembler and ability to create sideways RAM utilities for myself got me learning not only how to write assembly language but optimise it - I wrote myself a version of Tetris - full Mode 2 pixel (or 2 pixel actually sideways) movement, high score table it saved to disk, having to do paging multiple files in to memory off disk of the source to compile it, was the extent of my coding on the Beeb - that would have been way too late to do anything useful commercially as it was 1992 by the time I did that and the world had already moved on, but such a good platform for learning.
Jude is very generous and thoughtful. What a wonderful gift and gesture. Very cool, Jude, if you’re reading this.
Why thank you 🥰 I actually came out as trans in the 2 years since I sent it so am Diana now haha.
I wanted it to be clean and at least be as complete a set as I could afford at time hence all the extra work I did, although I was being entirely selfish by sending it at all cause I desperately wanted to see a video by Adrian on probably my second fav retro computer, with its big bro the Micro as my top!
@@atomoworkshop3327thanks for sending it in to share- don’t see these much here. Also, good for you being authentic to yourself. Congratulations
Finally seeing someone adding solder while desoldering.
I see so many people just fussing forever to get those pins clean.
A bit of fresh solder does the trick way better!
Great video as always! :)
Or just using fresh flux... adding solder is also adding flux to it...
@@steveoerkel735was just about to comment this. Use flux. Always use flux. Can never use too much
I've been doing that since I started desoldering, specially with most soldered stuff being the lead free solder, but old joints are a pain to remove without adding a bit of fresh stuff
Flux is your friend.
Lol, love the sound effect when you realized the chip wasn't even soldered in.
This was my first real computer. My Dad bought it in that year when Acorn were trying to get the Electron ready for the Christmas market, but missed. Plus, it looked on paper almost as good as a Model B yet less expensive. It was an awesome item of kit. I still have it in its original box with all of its original parts and software etc. in my loft. It's built like a brick and still runs perfectly well. I look forward to part 2.
I think what I like about this channel is that you insist on finding out WHY things don't work or why they were 'fixed' (or not) the way they were. I spent six years working with my dad's contracting company, and my dad was always looking at previous renovations or repairs and trying to figure out why the previous contractor (or owner) would have done things the way they did. (And the more bizarre the 'fix,' the more entertaining the sleuthing!) I loved that part of working with him, and I've never seen that kind of side-questing anywhere else but here in your videos.
Great computer and very popular in the UK in the 80's. Its basically a cut down cheap home version of the "BBC B Micro" that was in almost all schools. This meant when we got home we could continue any "Computer Studies" homework at home. The games were very good too. Will never forget Elite.
A little tip, when electronics like these has an AC input you can use a DC power supply, they have an internal DC rectifier, so it doesn't matter. The NES also has a 9V AC input, you can use a DC supply on either polarity and it works the same.
Adrian explained in the video why he didn't want to go that route. Some electronics use a charge pump to generate a minus supply from the AC input, so a DC supply won't work. In most cases, however, you are correct.
It works for most electronics but if a positive and a negative voltage is required you could simply use two diodes and two capacitors to charge them each in turns during every half-cycle or to supply the AC to a charge pump to generate a negative voltage from the rectified voltage without the need for an oscillator. Once I even had a computer (a weird "toy" computer for children with a monochrome dot matrix display) that came with an AC power supply and the computer also did kinda work with DC but then froze at the start screen because it seemingly used the AC to generate some timing (interrupt?) signal. (The "games" could also be sped up or slowed down by changing the AC frequency and you could even somewhat single-step it by switching the polarity back and forth "manually", which I used to win most of the games in basically no time since the time was calculated by the number of AC cycles while most other things still worked with DC and you only needed a few pulses to get to the next screen every now and then.)
Without analyzing the power supply and tracing all the outputs you can't be sure that DC *always* works… though trying usually wouldn't cause any damage (unless there is another transformer powered by the AC input or something alike that might cause a short when powered by DC).
You forgot the sender said in the note that the keyboard was tested as OK on another computer.
Another great video Adrian.
Ahhhhh my first computer from over 40 years ago! I loved it so much, spending hours typing BASIC programs in from magazines, saving and loading games from the cassette recorder and learning how to program for myself (which led to a career being a developer!). Lovely to see this again, it's like meeting an old friend 🥰
Oh the dark arts of tape loading! I remember with the Spectrum spending hours getting the right combination of volume, bass and treble so a program would load. Then often finding the 'perfect' settings wouldn't work with the next cassette you tried.
That ULA was hilarious. ❗
Plug a mono cassette player in and save out a BASIC program, then try to load it back in.
Merry Christmas.
"That seems like extreme penny pinching..." yeah, welcome to the UK.
Sort of ironic that this an old British saying (although the yanks still call their one cent coins pennies).
On my electron repair video the audio section was corroded and I do cover this, but it was also just very picky about the volume setting. Amazing work on the repair, what a mess.
Ah, that would fit with the comment I just posted based on a very vague memory - is there something called a Schmidt trigger in the circuit ? That’s the name of something I remember being told about.
@@sputukgmail it was a while back so I can't remember the details.
My brother and I used to have one that our parents got us for Christmas here in the UK, probably Christmas '83 or '84. Amazingly as soon as you mentioned not being able to LIST the program I said to myself 'OLD, use old'. Truly amazing what the brain has stored away. We upgraded to an Acorn BBC Model B a couple of years later, which we still have and it works, and an Archimedes A440, then A540, the A540 still works as well. Brilliant video, totally enjoyed the restoration. Fantastic !
This was my first computer. Fond memories, loved the keyboard.
I’m from the U.K. and had one of these around 1984/5. We had the BBC micro in high school, and I begged my parents for one at home. They bought me the Electron and made me go out and get a Saturday job at a butchers to pay them back 😂
I remember sitting for hours on end typing in line after line of basic out of magazines for free programs.
Thanks for bringing back great memories.
BTW Adrian, I recently saw people using a mechanical pencil to straighten pins. With the lead removed, it's the perfect size to slip over a pin and straighten it. Never saw it before myself.
I'd have thought inserting it into an empty ZIF socket would have done most of the work; wiggle the lever a few times & all pins should be (mostly) aligned
Great video. Never knew that a specific 6502 could slow down it’s clock.
As others probably already commented, you can use 19V DC for the Electron. I use an old Dell laptop adapter and it works just fine. And if you hit the BREAK key by accident, just type OLD to get your program back. And for LIST just type L.
You should really improve your BBC Basic skills cause it rocks 😊
Looking forward to part 2!
I'm pretty sure from ancient memory that O. L. was some muscle memory right there from using BBC computers in school.
A little anecdote for you, at school in the UK we had one BBC B for the whole school which for 99% of the time was used to play games in the lunch break. We would share time on it to program, play games etc, and yes to get the program/game back after hitting Break was to type OLD or O. as an abbreviation. BUT if you typed 0. (zero dot) it was classed as staring a new program and you lost whatever was in memory, OLD could not get it back from that point. It was so easy to mistakenly type 0. with the keys being so close. There was this one obnoxious kid at our school, who had been particularly obnoxious that day, and it was his turn to play "Snakey" after me, but I may or may not have accidently pressed Break, then 0. and I was like "Oh no! What a personal disaster!" He actually went purple with rage because he couldn't get the game back. Like full on purple. I remember it to this day. Must 45 years ago now. Simon Spolton, if you are reading this, I sincerely apologize. :)
@@bubo1it would have been possible to still recover most of the program if you’d gone in to edit memory directly - starting a new program would overwrite the initial bit of the program in RAM, but it wouldn’t clear the rest, and a single empty line 0 with a . In it, would only over write the first dozen bytes, and with a bit of “reconstructive surgery” you could get the vast majority of a program back ok…I may have had to go that on occasion - and having the first line of your own program being a comment could make that process a lot easier too ;)
@sputukgmail So you're saying there's still hope? 🤣 But I would have missed out on seeing someone literally turn purple. Like cartoon levels of purple. There was some phlegm and general rage related froth as well. Really was a sight to behold 🤣
Got to love in when the processing power on the power supply exceeds the entire computer... lol
I think in practice, that 19V AC connection to the expansion connector was actually used as a power input when using the Plus 3 disk add-on that was L shaped and blocked the power input jack. It had a beefier external power supply that fed through to the internal supply. Great video, my first machine was an issue 1 Electron and I have several along with some add-ons (Plus 1, Plus 3, AP4, Jaffa Mode 7, and the custom BT Merlin expansion - Acorn were left with thousands of unsold units after missing Christmas ‘83 and they got repurposed by British Telecom for various niche business applications). So impressed you persisted and got it working!
the internal psu will work off around 19vdc ok, many people have done so, but obviously the add ons wont,, the internal board has a bridge rectifier after the ac input,, the regulator circuit is switching and generates the -5v from an extra winding on its transformer
A plus3 has its own 21V supply, or was it 23V even. The floppy also covers the old power inputm
The Electron was my first computer, shared with dad and sister. Very nostalgic to watch this, great fault finding too. Looking forward to pt2 :)
Here in the UK, the C=64 quickly dropped in price to somewhere around £230, compared to the £399 for the model B (£299 for the 16k Model A) and £129 for the Spectrum (after its price drop). We are talking about 1984/85 when the Electron was arriving. For comparison the Atari 800 and later 800xl started around the same price as the BBC. Schools could afford them because of Government subsidies. Now, you hear a lot about the US Video Games Crash (which no one else noticed, because computers ruled everywhere else). But the Electron arrived during our own computer crash as just about everything but the Spectrum, Acorn, C=64, Amstrad CPC and Atari ceased production as their parent companies collapsed. And Even Acorn and Sinclair had to be rescued by other companies (Olivetti and Amstrad respectively).
Awwww you repaired my old friend.....Nice to see Adrian.
Way back in 82-83 ish, I bought one of these but soon got the Plus 1 and then the Disk Drive Plus 3.
I liked using the Defrag command on the disk drive as it used Video RAM to give it more room to work. This resulted in the screen being filled with what looked like white noise but I think it was the actual data stored in Video RAM then being moved back to the Disk, defragmented.
That repair job was really nice to watch and made me laugh to see the ALU being unsoldered.
What was with the original bodge wire being soooo long anyway? 🙄
If you look at the back edge connector, you will see 2 screw holes either side, these were for the mounting screws both on the Electron and Plus 1 and when all 3 were together, the whole computer was one solid construction and about as big as the BBC, not like the ZX81 and its flimsy 16K RAM Pack extension.
The Electron cost me £199, the Plus 1 was £60 and the Plus 3 was £199 if I remember rightly.....A lot of money back then...
I had a giggle @55:00. The RESTORE command is to do with READ and DATA statements when you kept inline data in the code. The correct command to recover your BBC BASIC code after a BREAK key reset is OLD. I guess they chose this as the antonym of NEW which is the command to wipe a program and start again without pressing BREAK. This is what I recall from nearly 40 years ago anyway.
When straightening out pins on ICS, if they are 0.1" pitch, it's handy to have some perfboard handy to see if everything lines up with a hole. Once it's pretty close, I push it into the board and give it a little bit of a nudge in various directions to even everything out.
I have 2 of these machines. One of them was not bleeping and the picture signal was scrambled. I inspected the main board and power boards, all looked fine. The solder side of the keyboard looked filthy, so I used a special circuit cleaner by WD40 and some cotton swabs to clean it up. I was very surprised to power it on afterwards to find the Electron was back to working as intended. The Electron was the first computer we had back when I was a child. I recently purchased the elksd128k expansion card, which gives 128k ram, joystick port and SD card storage. Also, I have the original plus 1 interface which works fine. This video was very interesting for me to watch. Great stuff fella.
BBC Basic includes the very standard NEW and OLD commands going way back…
Even Dr Wangs original Palo Alto Tiny Basic had these commands 👍🏻
I thought, I bet it’s something silly like the keyboard needs to be plugged in….never in a month of Sundays did I expect the ULA not to be soldered in and the wrong processor. That you found and fixed both is amazing!
This is probably the best looking 8-bit computer. It looks so modern.
Another great video Adrian. Just goes to show how important understanding first principles is ! Manuals contain errors, boards get revised and config isn’t always straightforward. These skills need to be kept alive and sadly all too often in industry i see these skills dying. Your style makes this process both fun and informative which let’s hope inspires more folk to build those analytic skills so needed in engineering.
The cassette interface plugs into the headphone socket and it's likely it needs a bit more 'volume' to make it work. Good job on the repair.
It could actually be the opposite, ie. standard audio levels tended to be too loud. I discovered this when many years after using cheap tape units, I was able to switch to a hifi unit and found recordings worked better wih a lower volume level.
I used to have an Acorn Electron, as a kid, and it was a heavily stripped down BBC Micro but I fully enjoyed my childhood experience with it and my mate, a CD Spectrum owner, was oddly jealous of the more colourful graphics the Electron had.
The one real issue with the Electron (& the BBC) was its distinct lack of RAM compared to other 8bit machines.
Damn autocorrect put CD in place of ZX.
Funny to see you working on the Acorn Electron. I myself am at this very moment busy with restoring the even older Acorn Atom. I already replaced some caps that where really bad (dry electrolytic that should be 22uF, but where 3.5 nF). I already got the "Acorn Electron" sign and the prompt visible on the monitor, so that part (6502 CPU, Video Chip, ROMs and memory) seems to work fine. The keyboard has some problems though. I already checked the key switches, and some where in bad shape (intermittent contact, stuck contact, or no contact at all). Treatment with contact spray has solved all but one key, so I am going to place all the keys back and cross my fingers. Lucky enough the keyboard works with a SN7445 and D8255, that are still available new (and cheap), so I have good hopes to get things working, even if the keys are not the problem. The coming days will be exiting...
I hope it all works out! I've yet to fix my original Electron which stopped working long ago, though I was able to establish that its ULA does work ok (swap test with another unit).
@@mapesdhs597 That hurts. Those ULA chips are very difficult, if not impossible, to obtain. That's a bleak outcome...
At least all parts of the Acorn Atom are not difficult to obtain and are still fabricated new. I nailed the problems down to the keyboard decoding logic, and going to test the suspected IC's involved. The prime suspects are the DM81LS95AN, because they are very sensitive to static. Another one is the DP8304BN, and lastly the D8255AC-2 can be faulty. A lot of the on-board IC feet have corrosion on them, so maybe I am going to replace a part, or all of them, with high-quality gold plated ones.
@@mapesdhs597 There can be problems with the socket on boards where the ULA is socketed. I don't think this was fully or widely appreciated, but it is definitely worth being aware of before concluding that the ULA is bad (which you've ruled out yourself, anyway). Some people have a repair strategy for the sockets, whereas others have actually managed to source new sockets, but they are somewhat difficult to procure.
@@paul_boddie Thanks! I think I got lucky with the ULA in my original unit being ok, but I've no idea to what extent this will be an issue with all the other Electrons I have (maybe two dozen), though I suppose it means I do have plenty of spares.
@@mapesdhs597 Two dozen?! Well, I guess you've got yourself a hobby, or maybe even a job, with all of those!
That is a serious WTF moment when you flip the board over, really made me LOL! 😂 Great to see you working on the Elk, of all the machines it's probably the one I know best as a bought one in 2021 and it came *without* a ULA so I made my own FPGA replacement that works pretty good in my issue 6. I wonder if your Elk was from the same batch I got mine. I think the story is that a huge pile of Elks were found after a fellow who used to repair them back in the day died and maybe yours was in the process of being desoldered? Mine had it taken out completely. Just a theory...
How did you do that? I'm guessing an FPGA but few have 5V compatible I/O.
@@MrDuncl ice40 FPGA and some level shifters. I got the basic plumbing from TubeTimes Graphics Gremlin design and Olimex Ice40 Dev board.
Years later and you can still hear the joy in Adrian's voice when something works. Wonderful.
RESTORE is a companion to the DATA and READ statements. Recall that DATA statements keep a hardcoded sequence of values embedded in the program; READ places each value from DATA statements into a provided variable, in sequence. RESTORE then resets the index to the beginning of the list so can re-READ from the top of the sequence. In at least some dialects of BASIC, an optional linenumber argument of RESTORE puts the index at the DATA statement on that program line, instead of the very first DATA (I think actually the closest DATA at or after the line number)
I love this stuff so much. Command prompt commands fascinate me to the point I read man pages for fun. I may never use BBC Basic 2, but seeing the logic spelled out is amazing! Thank you!
Was gonna post a similar comment 🙂. Long while since I've used a Basic DATA sequence LOL
I so enjoyed this video, I have a BBC model B and the Acorn Electron is the small brother. I learned 6502 on the BBC 50 years ago.
Another great video thanks! I have great memories of the Electron - my teacher gave me his one with software before he retired in 94..
18:40 Please tell me I wasn't the only one yelling "plug the keyboard in!!" 😂 Lovely to see the Elk in the basement at last.
Heh the only side effect of that is just pushing those extra letters when it's at the BASIC prompt.
I was expecting a sneek reset circuit on the keyboard.
No you weren't the only one xD. @adriansdigitalbasement the thing is that previous versions of the ELK don't boot without a keyboard, I have two with the ceramic ULAs and they don't boot at all, you get a black screen, it drove me crazy the first time I got one.
There's something about that computer that makes it one of my favourites in my collection! And love the keyboard.
I had an Acorn Electron - the younger brother of (and partially compatible with) the BBC Micro. It was a great little machine. I had the expansion unit, plus the disk unit.
I really regret getting rid of it.
The ULA (Uncommitted Logic Array) in the Electron was actually designed using the BBC Micro.
My first computer! Loved that little thing. My mother got it for me to carry on programming stuff I'd started at school on the BBC Micro.
Always good to see one saved.
Absolutely superb content. About 35 years ago I did a beginners electronic servicing course and was pleased that at the end I could diagnose and repair simple faults that where deliberately created on monochrome TV's - since then I have done zero field work and forgotten most of the theory etc but it does mean I can really appreciated fully the skills that have gone into this video. In addition I was once given an Electron and after typing a few short programs into it decided it was a very limited device that I didn't need in my life and sold it on eBay for £30 - little did I realise I had an important piece of computing history in my hands!
My first computer (and I still have it). After a reset you can type in 'OLD' and most of the times you have you're program back. Another funny thing is that you didn't need a datarecorder, but a regular audio tapedeck with a 5 pin din connector worked too :)
This is the best content i've ever seen about 8 bit era computers; excellent work, can't wait for part 2!
The idea that Electrons need specific 6502s because of the 40us clock halt in modes 0-2 is mostly a myth. I tried many different types of 6502 in the Electron while I was designing an accelerator card for that system, and every chip bar a very old MOS 6502A part worked fine - and that chip was unstable in all video modes, so was possibly a re-marked 1MHz chip that couldn't cope when run at 2MHz. Some issue 6 Electrons actually shipped with Rockwell R6502APs installed, so the CPU in Adrian's machine may well have been the original.
Also, as a point of interest, you can fit a Rockwell R65C02 into an Electron and it'll work just fine. Doing that permits the use of BBC BASIC 4, which requires a 65C02 and has some nice performance improvements.
Damn. Seeing this flooded me with memories and nostalgia. I grew up in the 80s/90s and my dad was a programmer. I'd go to school and my favourite class was anything involving the computers (BBC/Acorn) and then my dad would let me do homework on his Acorn or Commodore. I can't see the old floppy disks (real floppy ones) without thinking about these.
Thanks to you and the person sending it in. ❤
I learnt BASIC on the Acorns.
Nice video! I own an Acorn Electron myself and it's pretty deaf on the cassette input. It doesn't work with sound cards or smartphones as input, probably due to improper impedance matching. But if I feed it from the headphone output of my hi-fi amplifier (even at low volume), it can interpret the virtual tapes without any problems.
Hi Adrian. I inherited an unwanted Electron recently. It wasn't working so I replaced the CPU with a R65C02P3 and also use a bog standard 12v wall wart to power it. All works really well now. Thanks for all your resources.
I had the Electron back in the day (couldn't afford the BBC machine, so had to make do with it's baby brother) ended up with it fully kitted out with floppy drive, expansion unit and (quite rare I think) a mode 7 adapter. I got quite good with BBC basic and could get by with some assembly code
Me too. Plus 1 and Plus 3 with ADFS. I also had a 6502 second processor that plugged into a cartridge socket that brought it close to the speed of a BBC.
I had an Electron as a kid, and got the Plus 1 expansion interface. AcornSoft made a number of useful cartridges and I had several, including Acorn's LISP interpreter. I also has and a disc interface cartridge so that I could use a standard BBC 5.25" disc drive (rather than the 3.5" Plus 3 expansion) as that let me swap disc back and forth to the Beebs at school. I also made my own Econet (well actually Amcom E-Net) interface as part of my A Level Design & Technology course project. Happy days!
If you press BREAK you can issue the command OLD and then your BASIC program can be LISTed or RUN. Even after a CONTROL BREAK.
I was taught to program on a BBC Micro in the 80's. They were in all Schools in the UK around that time. I had a Spectrum at home though.
Loved this machine, it was my 2nd computer after a ZX81.
Me too, kit built ZX81 then BBC B followed by a Master and an Archimedes
I went BBC, A3000
The limitations of the Electron led to some ingenious solutions. For example, the sound was pretty basic (especially when compared to the C64) and only a single channel, so some bright spark came up with the idea of using the cassette relay as a rudimentary drum machine to accompany it.
On the PSU, uh no. Take a ten second look at the PSU board: it doesn't need AC to create a negative rail at all, it uses a similar system the ZX spectrum does: it's switching.
I power mine from a laptop PSU kicking out 18v DC.
Using that relatively expensive picopsu is bonkers.
IC 14 is an XOR. PAL turns the color wheel upside down every second color. NTSC doesn't do that. That's why in NTSC the XOR on one pin is permanently set to GND. With PAL the signal comes from a flip-flop.
Not every second colour. Every other line in time. (Not in space.)
The audio leads plugged into the headphone output, not the line output, and it was always very finicky about the volume settings. You would have to spend a lot of time initially getting it dialled in to exactly the right volume to get a reliable load. Once you'd found the sweet spot for that particular cassette tape player it was fine, but finding the sweet spot took time.
Great video thanks, and the bit where the ULA was unsoldered was priceless - so unexpected 😅
As some have alluded too, this is one of your best videos to date! Two Thumbs Up for that.
Before Commodore bought out MOS Technology, MOS has licensed the manfuacture of the 6502 to other (Rockwell, Synertek, Western Digital Design, Hitachi, and others). I know in those early days, Apple used the Syntek ones and Atari used the Rockwell ones. And the 6502 was used in many things in those days besides Personal Computers.
But these licensed companies tried to make their own improvements to the 6502 and thus created a set of "Illegal Op Codes" different to the other 6502 made. This is where things shined for some and failed (like in this case) for others.
One of the few things Rockell used the 6502 (More like the 6507 and 6509) was a microcontroller for their aerospace industries. But the 6507 was also used in the Atari 2600 and the 6509 was used in the CBM II. Thus timing for the 6502 on these Rockwell systems has to be very tight, and their version of the 6502 (at the time) was the first 2MHz 6502 (as used on the Atari 8bit). Thus such a timing delay used on this Acorn (and other systems) worked well on other 6502s but fails on the Rockwell.
Oh the horrors! A partially desoldered and banged up ULA! That would have been the death of many machines. But you got it working! You turned somebody's trash into a treasure!
So what's next? Amstrad? MSX? More TRS80 & Coco stuff? When was the last time you did a TI 99/4A? Maybe you will be lucky and get a Soviet home computers. I had one but had to sell it to keep from going homeless in the 1990s; but while I has it, it was literally a PDP-11 on a chip in a small all-black Vic20 case. A very strange machine.
What I think also plays a role is that those UMC 6502A CPUs were mostly made in the 90s. I assume on a significantly better manufacturing process than the early 6502. Therefore the reason for that 10us clock cycle may not have existed and the CPU could be certified for longer clock cycles. They are still real NMOS 6502s though and support the undocumented opcodes.
I always thought it was just down to the original 6502, even CMOS editions, not being implemented with static registers. Slow it down to much or worse stop the clock for too long and the registers become invalid, including PC, and computer crashes. I guess there's so many variants of the 6502 that there's all sorts of problems to find when tinkering with the clock.
I couldn't see anyone else comment this, the command to bring back a listing after pressing break is "OLD". Also, there are some hard coded "quick commands" - press and hold the Caps Lk key and "O" for OLD and "R" to run. CHAIN (to load from tape) is CAPS+K. etc.
This video has made my Christmas holidays, great to see the Electron getting some representation on your channel. I love my Electron(s). I had one back in the 80's with a Plus 1 and Plus 3. Recently I was lucky enough to get 2 Electron's that I have been slowly building up to two different specifications. One is a copy of my original, with a Plus 1 and Plus 3, the other is a 3rd party expanded machine. With Slogger RomBox, Plus 1, Slogger Pegasus 400 disk interface + PRES 3.5" floppy drive. There are so many expansions available now with lots of hobbyists developing things, including a WiFi cartridge, SD card adapters with MMFS, Econet adapters, PiTube Direct for second processors, port expansions to bring in most if not all of the ports that the BBC B has. Would be great to see videos of any expansions you may get in the future. Good luck.
Great video! Merry Christmas!
Hi Adrian, so glad to see u again. I'm so into the way you solve problems and have seen almost all your videos since "How to remove chips without damaging the circuit board" posted 4 years ago.
I encountered a problem when removing chips recently. It's found that the chips are hard to be removed with the tin on the bottom. I've tried Solder paste, heat gun and heating platform but none of them worked. So i come for help, wish you could offer some precious advise or experience.
Looking forward to your next video.
Love your show, merry christmas
The Electron was our first family computer 😊 (Greets from the UK)
The Electron has the best sounding keyboard ever!!!
One of the difference with the BBC model B was the Mode 7 Graphics, the Electron didnt have it. The Mode 7 Graphices was also known as The BBC's Ceefax or Teletext that was broadcasted by the Broadcasters Also there was a Plus 3 interface expantion this had a 3.5 inc disc drive with Disk Filing system (DFS) or Advanced Disk Filing sytem (ADFS).
That sound effect was so perfectly timed! First time I think? Great video and lots of fun!
Which one? At what time into the video?
@@ropersonline about half-way through when he takes the motherboard out of the case and turns it over! I was glancing away from the screen for a second and it was the perfect thing to make me snap back! LOL
@@Midcon77 Ah, thank you. It's at 31:21, for the record.
Great video Adrian. Looking forward to part 2.
👋👋👋Hello from me on my boat on a canal in the UK.
I used to have one of those Acorn's too 🙂
Merry Christmas Adrian, I love your Acorn Content!
I actually did have a BBC Model B and then a BBC Master 128 (later with the Turbo Co-Processor fitted) and then I migrated to the Acorn Archimedes and Ultimately the PC. The BBC was very expensive for the 1980's at around £400 (£1,300 in 2023) and then all the upgrades over the years. Still nothing better for Basic and 6502 assembly programming 😁
The Model B was really aimed schools etc rather than home users. The parents who did buy them (like my boss) thought having one would guarantee their kids got to Oxbridge 🙂.
As I recall, the BBC A was £399, and the BBC B was £499 at least initially. The upgrade part for the model A to B cost less than the difference and the A was available to buy earlier so my aunt and uncle got one and my uncle, being an electronics wiz, did the upgrade to make it a model B…although I think theirs only got the RAM and something else upgraded, not all the expansion ports and they later got a proper model B instead.
But yeah, significantly more than the C64 which I think was £399 when launched, but was already down to maybe £299 by the time the BBC B actually became available. It was that kind of price difference. And I vaguely recall the electron started advertised at £299 but was soon £199…but it’s a long time ago to remember ;)
Ah - Wikipedia says my memory sucks: “introductory prices
£235 Model A, £335 Model B (in 1981)”
@@sputukgmail I think those prices soon jumped up to £299 and £399.
@@MrDuncl I’m glad someone else remembers the x99 prices for the Beeb - I was saving to get myself one at the time and that was the figure I remembered. We ended up spending much more as my mother went halves because she was setting up a typing service - so we ended up spending more like £700 getting the Beeb B and the double disk drive (and threw jn a copy of Castle Quest along with WordWise+ ). All this is making me want to dig out the two Beebs I’ve still got (including the one bought back then, and one I got at a peppercorn rate that used to be a doomsday machine) but I don’t want to find they don’t work anymore. While I leave them boxed up, I can image they work fine :)
Amazing video Adrian! 🍻 Thank you for your work! 💪
Happy Christmass Adrian. Love your videos.
This was so much fun to watch. And informative, too. Thank you!
merry christmas and great video!! :)
Fantastic. What an entertaining odyssey! Great progress so far!
Absolutely love your enthusiasm Adrian 😊😊😊😊😊
loved the christmassy desoldering tune 🤩
Merry Christmas from the UK Adrian :)
Merry Christmas from Norway Adrian!