This Acorn Electron won't load anything from tape #repair

Your decision to do this full time is completely validated. Your ability to convey your expertise and thought processes in a diligent and understandable way, should not be under-estimated! Well done...

That “data? Rewind tape” message brings back so many bad memories from 40 years ago! You could easily spend an hour trying to load Elite.

I was watching this on my TV. I took the time to log in to my account so I could comment: the outtake was absolutely worth waiting for.

If the attempted repair was done in the 80s, access to an oscilloscope would have been limited. Access to schematics might have been available, but as you point out, the diode isn't in the schematics. Even access to a multimeter with diode testing would have been somewhat pricey. Not to mention, the years of experience you have with troubleshooting 8-bit computers would have been confined to electrical engineers. So parts cannon was the only method we had unless we knew someone in university.

The first of those op-amp circuits is simply an amplifier to increase the signal strength from the cassette player as much as possible. The second stage is a low-pass filter to get rid of any frequencies above the data frequencies, and the final op-amp stage is a clamping circuit to limit the amplitude of the signal.

Remember my Acorn Electron cassette lead having three jacks; input, output and control to stop start the tape.

You have to look back in awe and appreciate what 6-11 year olds in the UK were being exposed to in the 80s via BBC Basic and hexadecimal checksums. It really is a sight to behold. And to reinforce this, there was a "game" on the BBC Micro called Granny's Garden. Most student's passed it off as a game, but actually this "game" was a kinda like "The Last Starfighter" in that students who SOLVED the dragon section, were actually solving LOGIC GATES. This to me is incredible looking back at what the BBC and the Government were doing.

First comment! Yay, my old BBC Master 128 is seeing some more use! 👌 All the best from Cambridge UK 🇬🇧

Yes, I had an Acorn Electron many years ago. Spending ages and ages waiting for games to not load from tapes. Happy memories. 🙂

Nice find with that diode! Here’s my quick circuit analysis, ‘cuz I like analog and audio electronics: Second opamp looks like a Sallen-Key two-pole low-pass filter, cutoff at 4.1 kHz. Third opamp is a symmetrical “soft” clipper, to make the signal very square, over a wide range of input amplitudes (as you stated!). They’re being tricky in the clipper, wiring transistors as diodes. I’m guessing it was easier and cheaper to throw on two more BC239 transistors than to source small-signal diodes just for this part of the circuit.

Different ring 🎉❤

Old timer tip: check for the little pad thing under the tape that pushes the tape against the reader head. Sometimes it would sag a little, causing the tape to not make good contact with the head. If you remove it and fold it so that the pad is a little higher, everything works wonderfully again. Regards from Argentina!

I admire your repair abilities! Congrats on narrowing down the issue to 1 simple component and fixing this machine! That little outtake at the end was fun! :D

Couple tips. First, azimuth and cleaning of the cassette deck. Bad azimuth causes higher frequency tones to blur together. Easy to set if you listen to some music, adjust the screw until it sounds most crisp (most high-frequency details audible). Next, crank that volume! You'll get more dropouts if the volume is too low at the "barely detectable" edge of the signal. Hey, fun watch none the less!

The BBC loads tape programs in blocks. The counter is the block count. If any block gets miss read you can wind back just that block and try again rather than re-start from the start. The DIN connector also supports motor control so the computer can stop the tape between programs.

Watching you put the cassette down on top of the cassette player speaker reminded me of the computer reseller where I worked in the early 1990s and the office person religiously backed up her computer to DC2120 tapes. She stacked the tapes on top of a clock radio on her desk once they were written and "verified". The only time that the backups were needed, many of them were too corrupted to restore sufficient data and about a months work of data entry had to be recreated and manually entered.

Good job! As for shotgun troubleshooting... if you've got a fat supply of every part, it's a really fast way to get stuff running. In fact, that's the DoD system of aircraft maintenance: replace every box that might be wrong to get the plane running, sending all of the suspect boxes bask to supply. Then supply sends those suspect boxes to repair centers to check out, where most run their test programs fine and only a few need to be actually fixed. Since boxes are filled with cards, you can recursively apply the shotgun approach ;)

I was a teenager running a small shop for one of the UK distributors for Acorn back when the Electron was released. It was very disappointing having been a BBC user for a while to see how much of a poor relation this was. The slow speed was an issue obviously but the thing that broke a lot of games was the lack of Mode 7 graphics. A lot of games etc. used this for in-game text because of its low memory requirement. A lot of BBC Micro software will run quite happily though, albeit slowly, but there was enough incompatibility between the 2 machines to make it frustrating and hit sales figures. I think if they'd made it as a BBC with ports removed but still running at full speed it's impact on the market would have been much greater over here. As it was, it was a mere shadow of the BBC Micro.

Ah the good old hexadecimal counter of tape loading on the Acorn machines.

taught myself to juggle waiting for tape loads on the BBC :)