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Old 7th Mar 2021, 11:40 am   #21
SiriusHardware
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Default Re: Enhancing PETs and other Vintage Computers

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Originally Posted by ortek_service View Post
BTW, it appears in an earlier post that HDD was mistakenly referred to instead of FDD (especially with reference to the 1541). I don't recall there
I do suffer from occasional brain-outs. The 1541 would be slow indeed if it had been an HDD. Thanks for all the other info.

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I never had a HDD for my (also original) Atari but, I certainly used it a lot and have 100s of floppies... I will look into the Satan.
Strictly speaking, 'Ultrasatan', as there was an earlier incarnation of it called the 'Satandrive'. (Again, don't ask why the unwholesome names). The creator of the units, 'Jookie', no longer makes them himself, production has been taken over by someone called 'Lotharek', apparently with Jookie's blessing (I went so far as to ask Jookie whether he was actually OK with that before buying one).

In the meantime Jookie went on to make a successor which is called 'CosmosEx' which has gone through versions 1, 2, 3 and a cut-down version called MicroCosmos. CosmosEx has a lot of features which someone just wanting a HDD substitute won't need, so I think MicroCosmos was created for that purpose and is probably the closest current Jookie equivalent to the UltraSatan (which by the way is also still in production as I write this).

The availability of all these HDD substitutes for the ST then spawned a separate special interest area, that of converting original titles, often originally made to run from a handful of floppies and save games onto floppies, to run entirely from HDD - so you can now find SD card images full of software painstakingly modified and patched to run seamlessly from HDD. Most of that work has been done, with no thought of any reward, by just one or two individuals.

Way back when, I spent hours and hours working my way through the many classic Spectrum titles I owned, converting them to load and run from Microdrive. All of that work was carefully stored for many years in a proper Microdrive box but when I came to check them over a few years go I found to my absolute horror that none of them were readable (It wasn't the pad issue, I knew about that). That was what prompted the purchase of the Vdrive, but I'll never get all those hours and hours of work back again.
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Old 7th Mar 2021, 10:55 pm   #22
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Originally Posted by ortek_service View Post
BTW, it appears in an earlier post that HDD was mistakenly referred to instead of FDD (especially with reference to the 1541). I don't recall there
I do suffer from occasional brain-outs. The 1541 would be slow indeed if it had been an HDD. Thanks for all the other info.


Way back when, I spent hours and hours working my way through the many classic Spectrum titles I owned, converting them to load and run from Microdrive. All of that work was carefully stored for many years in a proper Microdrive box but when I came to check them over a few years go I found to my absolute horror that none of them were readable (It wasn't the pad issue, I knew about that). That was what prompted the purchase of the Vdrive, but I'll never get all those hours and hours of work back again.

I've got both a Pi1541 and a Tapuino, that a work colleague gave me these after designing and getting his own custom PCB's made. But not had chance yet to have a go with these on my C64's / VIC-20's, only some of the multi-ROM EPROM Cartridge boards he'd also done.


I do recall also trying to transfer some Spectrum games etc. to Microdrive back then - but I think with limited success, as a larger System variables area of RAM was required when Interface-1 was present But maybe I wasn't aware of the right techniques to use and I recall there being Replay etc. 'Tape-to-disc' memory-grab devices, to aid in this.

I think I probably got rid of all my original Microdrive cartridges when I sold it all to bet a Beeb
- Where I had rather more success with transfers, loading program into upper screen memory, than copying it back down to Page &E00 once DFS was deactivated, that shifted Page upto &1900 etc.
I've still got boxes full of all my original Beeb 5.25" floppies, but I haven't tried most for a few decades, so they may well have deteriorated from what I've heard others have been finding.

I have since acquired some Merlin Tonto / ICL OPD Microdrive cartridges, for use on one of these / a QL I need to fix one day. So I'll have to look and see what state they're in. I've not really noticed any issues with audio-cassettes I've got from the mid 80's. And do also have many video-cassettes, inc. some old Betamax & N1700/N1500 ones, I'll have to checkout sometime.

I always wanted some Laservision discs / BBC Doomsday system, but seems many of these are now getting bit-rot that some early CD's also had issues with (Plus with the very first 'Gold' unbranded CDR I bought, I found the top coating all flaked-off more recently - So much for the often mentioned 30yr life for these ! And some dye-ones maybe rather better)
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Old 7th Mar 2021, 11:03 pm   #23
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Default Re: Enhancing PETs and other Vintage Computers

The cartridges are likely to be OK but, you must replace the Felt on them before use - open carefully as it has likely already fallen out...

https://youtu.be/bzRc6S7cCHk

People seem to get a lot of success with 8 track felt available in online marketplaces - cut to size with a scalpel.
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Old 7th Mar 2021, 11:31 pm   #24
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I remember there was an ongoing war between the software vendors and the makers of those hardware snapshot devices. The early ones worked by paging in their own version of the ROM (with some changes) and so some software protection schemes countered that by encrypting the code on the tape and decrypting it by mathematically manipulating it against the bytes in the ROM to reconstruct the original code. But if the ROM didn't contain the original code, then the reconstructed code came out wrong...

Unfortunately that backfired when Amstrad took over and made a wholly unnecessary 'vanity' change to the 48K PROM to make the startup prompt '(C) Amstrad 1986'. Needless to say it broke a few loaders.

I never had one of those hardware devices so I had to do everything the hard way, which made the loss of all that work doubly annoying. There's no way I would be able to do it all again now, I've just lost so much of that knowledge.

When attempting to make games load from Microdrive you could do things the original vendor wouldn't have, such as loading part of the code into screen RAM to hold it there while you did other things and then swapping it into its rightful position last-moment. Temporary garbage on the screen was a small price to pay for having the software load in 10-15 seconds rather than 4-5 minutes.

Tim, as I mentioned, I was already aware of the pad problem and none of my original cartridges were affected by it. I bought some more cartridges shortly afterwards and they did have bad pads, some like melted treacle, I didn't even try to use them. They were sent back for a refund. Even back in the day I got used to having to take out, reshape and reposition the pressure pads every now and again.

Anyway as we've already said, the Vdrive, the fully electronic replacement for the innards of the Microdrive, is the perfect antidote to this problem. The Interface One doesn't even know the difference. Available in a version for the QL as well, I believe.
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Old 7th Mar 2021, 11:35 pm   #25
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Default Re: Enhancing PETs and other Vintage Computers

I've been seeing adverts for dual-port RAM lately. Now, that has some interesting possibilities ..... I may have to check that out. I quite like the idea of two independent processors being able to share a common chunk of memory .....
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Old 8th Mar 2021, 4:29 pm   #26
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I've been seeing adverts for dual-port RAM lately. Now, that has some interesting possibilities ..... I may have to check that out. I quite like the idea of two independent processors being able to share a common chunk of memory .....
Dual-port RAM has been available for quite a few decades, from compaines like IDT & Cypress. e.g.
https://media.digikey.com/pdf/Data%2...016,017a_8.pdf

But these are often rather expensive - especially for larger sizes.
And only really required when one-side need to be continuously running uninterrupted, on a uP etc., whilst you read / write from other side with address-contentions automatically resolved - eg On an In-Circuit Emulator / Debugger.

So a cheaper approach is usually to make a 'half-duplex' version, from a standard SRAM and Tristate-buffers either side, to switch which side has access. And allows you to freeze memory contents, from a running system, and read it out / alter its contents. This is what most EPROM-Emulators do. (Although there's talk of simplifying a recent open-source design, that also has a serial-EEPROM to make it copy to / from to make it non-voltatle, by just using a Parallel FLASH memory device which is fine for ROM but not RAM emulation.)
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Old 8th Mar 2021, 4:38 pm   #27
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>>
>>
Anyway as we've already said, the Vdrive, the fully electronic replacement for the innards of the Microdrive, is the perfect antidote to this problem. The Interface One doesn't even know the difference. Available in a version for the QL as well, I believe.
And hopefully this also fixes one of the major design-flaws with the Microdrives - That if you switched the system on with a cartridge inserted, there was often a brief magnetic-pulse onto the tape section in-contact with the head, corrupting it.
And I lost quite a bit of stuff on my cartridges, due to forgetting to pull out the cartridge before switching on.

So I didn't regret the switch to the Beeb, which could be set to auto-boot from disk at power-on, and disk-drives that were find to leave the disks in at power-up - As many computers booted from disks OK.
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Old 8th Mar 2021, 4:51 pm   #28
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Real Microdrives had one other horrific 'quirk', if the system crashed while writing to the tape the thing would sometimes just keep going, and in the process erase / overwrite the whole tape. I really don't miss them at all. The QL's determination to press on with the Microdrive was the reason I finally broke up with Sinclair and defected to the Atari ST.
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Old 8th Mar 2021, 4:54 pm   #29
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Agree, the BBC B was a 'proper' computer in every respect, but unfortunately for me they were a rich kid's toy and out of reach at the time.
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Old 9th Mar 2021, 1:00 am   #30
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Yes, the Beeb was quite expensive compared to a Spectrum (Although the UK price of C64's wasn't too far behind that of a Beeb). And most must have been sold to all of the Schools etc, as the official learning computer with only a few Schools usng (equally expensive?) RML's or even Spectrums, with only the richer home users buying Beeb's new.

But you could buy the Model A for £300 rather than £400, then buy all the parts for to upgrade it to the Model B for a bit less than £100 / buy only the parts you needed, as required)
- The rather old 8271 FDC IC at £40, was a major part of the cost of the Model B, but then again you didn't need an extra Interface (1)
(Although even the cheapest Disk Drives without a PSU, were still much more than Microdrives).


I had considered getting an Electron, but by the time you bought all the extra interfaces to make it like a Model B, it ended up costing nearly as much
- And you still had a computer that wasn't as good / compatible, due to compromises in the Electron's ULA over the dedicated video IC's and lack of Tube interface for alternative processors (Although ETI did a project for an Electron one). So I went for a secondhand Model B, then a disk drive a bit later. And Beeb still works AFAIK, > 35 years later.

Whereas several Spectrums died partially (not seeing Interface-1) or totally on me - Fortunately whilst under guarantee, and got free upgrade to a +
And it wasn't always my fault of plugging in interfaces, whilst still powered-up (with +9V and +5V next to each other on edge connector, just waiting to be shorted together, if connector not exactly aligned).
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Old 9th Mar 2021, 1:27 am   #31
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Real Microdrives had one other horrific 'quirk', if the system crashed while writing to the tape the thing would sometimes just keep going, and in the process erase / overwrite the whole tape. I really don't miss them at all. The QL's determination to press on with the Microdrive was the reason I finally broke up with Sinclair and defected to the Atari ST.

The Microdrives (which they did manage to squeeze 100K on QL, rather than previous 80 odd KB on Spectrum, using the same cartridges), wasn't the only issue with the QL.

Also( ignoring the larger ROM's than originally room for issue), trying to claim the QL were 32bit Computers, when the 68008 CPU was crippled with an 8bit bus, was a bit misleading
- At least the 68000-based ST & Amiga were only referred to as 16bit.
And the QL's BASIC print to screen benchmark was actually slower than a (Not the fastest) Spectrum!

On simple 8bit Arithmetic, the 6502 was much more efficient than the Microcoded 68000, doing this in less cycles. So it was only the higher 8MHz clock rate of the 68000 that made it as fast as a 2MHz 6502 for doing this. (Although the 68000 did have many more registers and instructions that could do much more, for better programming efficiency & compiler support)

And after consider the 68000 / experimenting with the NS 32016 (rebranded 16032) for their future computers, the key designers of the BBC at Acorn decided they could do much a much better job themselves than the 100+ trying to get the 32016 working correctly, after being inspired by the small team in a house that did the 6502.

So Acorn actually did a true leap from 8 to 32bits, with their hand-designed / optimised ARM RISC , that didn't need that many more transistors than were used in the RISC-like 6502 CPU. Although they did apparently have an 800 line BBC BASIC program to simulate the ARM, as well as running the instruction through it on cards, to ensure there wasn't execution bottlenecks.
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Old 9th Mar 2021, 12:49 pm   #32
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I lost count of how many Sinclair printers I took back to Boots back in the day as they kept failing.....I see some on ebay that claim to be working even now. This surprises me.

Colin.

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Yes, the Beeb was quite expensive compared to a Spectrum (Although the UK price of C64's wasn't too far behind that of a Beeb). And most must have been sold to all of the Schools etc, as the official learning computer with only a few Schools usng (equally expensive?) RML's or even Spectrums, with only the richer home users buying Beeb's new.

But you could buy the Model A for £300 rather than £400, then buy all the parts for to upgrade it to the Model B for a bit less than £100 / buy only the parts you needed, as required)
- The rather old 8271 FDC IC at £40, was a major part of the cost of the Model B, but then again you didn't need an extra Interface (1)
(Although even the cheapest Disk Drives without a PSU, were still much more than Microdrives).


I had considered getting an Electron, but by the time you bought all the extra interfaces to make it like a Model B, it ended up costing nearly as much
- And you still had a computer that wasn't as good / compatible, due to compromises in the Electron's ULA over the dedicated video IC's and lack of Tube interface for alternative processors (Although ETI did a project for an Electron one). So I went for a secondhand Model B, then a disk drive a bit later. And Beeb still works AFAIK, > 35 years later.

Whereas several Spectrums died partially (not seeing Interface-1) or totally on me - Fortunately whilst under guarantee, and got free upgrade to a +
And it wasn't always my fault of plugging in interfaces, whilst still powered-up (with +9V and +5V next to each other on edge connector, just waiting to be shorted together, if connector not exactly aligned).
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Old 9th Mar 2021, 6:37 pm   #33
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I presume that was the classic silver conductive-coated black-paper stylus on rubber belt spark-eroder, that was more of an ozone producer than a printer! I'm sure I've got one, I picked-up cheap quite a few years ago with some paper - but I imagine that's probably degraded a bit.

I did borrow one back in the day when I had my Spectrum, and did print a few screen shots with it, I probably still have - but no doubt paper has deteriorated. And I also used the Interface-1's RS232 interface with a lead to use a friends Paper Tiger dot-matrix printer, his dad had got from work.
I did also buy from Comet a Commodore 'Serial' 4-pen Colour ALPS-mech printer-plotter, thinking I could get it working on RS232, with the right connections. But I hadn't originally realised it used Synchronous-Serial so gave up and got a refund.

The first printer I actually bought an used was a battery-powered Brother HR5, that could actually print to A4 standard size paper - either using short-life thermal transfer ribbons like labelling machines, or direct to thermal paper (like many current till receipts use, that go black if they get hot).
I had to build my own (Z80 PIO) Parallel-port interface for it, with some code to make it work with standard printer commands - From Sinclair User IIRC.

I must have sold that (expensive to run), printer to get a used LX80 (I've still got) dot-matrix printer for the Beeb, where I wanted an Epson-compatible printer that quite a bit of software required. And used that a lot.
And I also got a surplus Sharp Colour 4-pen ALPS-Mech plotter, that unlike the Commodore version had a standard parallel port interface, so could use it from the Beeb, once I'd swapped MZ-80K connector to a more-standard one

I'm sure I've now got a few Parallel / Serial interfaces for Commodores, as well as acquiring another Commodore 1520? mini colour plotter again - where it should be a lot easier to make an interface for it to more-standard interfaces - probably using an RPi-Zero etc, like used on the Pi1541 emulator.
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Old 9th Mar 2021, 6:58 pm   #34
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I dodged the ZX printer issue by buying an Aphacom 32 instead - instead of printing on tin foil they printed on thermal paper, which was fine as long as you didn't mind your listing fading to invisibility in a matter of months. I may actually still have that printer, will have to have a look.

One thing you don't seem to see a lot of is interfaces which allow old machines to use modern USB-connected printers, or am I behind the curve there?

Probably the most pressing problem faced by older home computers is the lack of a suitable legacy display to connect them to, especially those like the ZX81 (to which happy 40th birthday this month, incidentally) which only had a UHF RF output.

In most cases building a composite-out buffer inside the original ASTEC modulator is not too difficult but it is increasingly the case that modern displays are only coming with HDMI inputs, so in the short term there are gong to need to be more and more solutions which convert composite video to HDMI or even monitor the screen RAM directly and render its contents as HDMI output, bypassing the original video-out scheme altogether. I think Tim mentioned that this already happens on the Spectrum NEXT and Julie was thinking of the same sort of scheme for PETs.

Last edited by SiriusHardware; 9th Mar 2021 at 7:14 pm.
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Old 10th Mar 2021, 1:47 pm   #35
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One thing you don't seem to see a lot of is interfaces which allow old machines to use modern USB-connected printers, or am I behind the curve there?.
The problem with a centronics-to-usb converter or similar is that you would need software specific to the emulated printer and the destination printer. For the Atari you can use an SIO2PC interface that connects the Atari SIO bus to a PC or Raspberry Pi and that will emulate floppy disks, and the software I had back in the day also "emulated" a printer by taking the data from the SIO interface and printing it to CUPS (on linux) or to the Windows printer. I think there was a similar device for the IEEE488 PET interface and I would imagine for the C64 IEC interface.
If your printer has a Rasbian driver you could fairly easily make a program that connects GPIO to a centronics port and prints the captured data (stripping out or converting escape sequences?) to a USB printer. I'd be surprised if someone hasn't already done this.
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Old 10th Mar 2021, 4:34 pm   #36
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Back in the day the Epson command set was king, so even other manufacturers like Brother, Panasonic, etc, could be communicated with via Epson-compatible control codes. Each printer had its own unique non-Epson codes to support its own special features but you could always do basic printing just by telling your computer that the connected printer was an Epson.
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Old 10th Mar 2021, 8:50 pm   #37
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This is the sort of device you refer to...

https://www.sellmyretro.com/offer/de...nt-model-37159

Almost all ZX Printers have now failed or are about to due to the rubber toothed band rotting. If you have one make sure you do not lose the little metal pins - one on each side of the old ribbon and the little caps which hold them in. Someone is 3D printing a replacement. There is also a repairer who had some made but, offers them only as part of his repair service as they are fiddly to do - as I have found out - especially when you have lost one of the pins.

I do have an Alphacom and it works great it is even possible to still get paper - if anyone wants just a roll or two let me know as they have to be bought in boxes of 20...
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Old 13th Mar 2021, 6:47 pm   #38
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>>
>>

Probably the most pressing problem faced by older home computers is the lack of a suitable legacy display to connect them to, especially those like the ZX81 (to which happy 40th birthday this month, incidentally) which only had a UHF RF output.

In most cases building a composite-out buffer inside the original ASTEC modulator is not too difficult but it is increasingly the case that modern displays are only coming with HDMI inputs, so in the short term there are gong to need to be more and more solutions which convert composite video to HDMI or even monitor the screen RAM directly and render its contents as HDMI output, bypassing the original video-out scheme altogether. I think Tim mentioned that this already happens on the Spectrum NEXT and Julie was thinking of the same sort of scheme for PETs.

It's surprising there hasn't been much coverage of ZX81's 40th - BBC Click recently mentioned BBC's 40th & TNMOC held an even last month, but it seems that isn't actually until Dec.

Well there are quite a few converters out there.
If you do still have VGA inputs on the monitor then the GBS-8200 etc are quite cheap (< £15 for PCB / some cased ones): https://retrogamingcables.co.uk/GBS-...-VGA-CONVERTER

And if you need to go to HDMI, then these are < £6 on a certain online auction site - Although a bit more here:
https://thepihut.com/products/hdmi-t...hoCKQMQAvD_BwE

You could also use an old PC TV capture card to take RF output direct, or take composite for better results (or use an external USB Video-digitiser, if you haven't got a PC with PCI slots for the capture cards), and show it in a full-screen window. Might be also able to use an RPi, for something smaller / lower power, as these are also often used with CCTV cameras (although maybe direct digital output, rather than composite and digitiser)


But maybe need a genuine line-scanned CRT, for use with light-pens / guns!

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Old 13th Mar 2021, 7:13 pm   #39
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This is the sort of device you refer to...

https://www.sellmyretro.com/offer/de...nt-model-37159

Almost all ZX Printers have now failed or are about to due to the rubber toothed band rotting. If you have one make sure you do not lose the little metal pins - one on each side of the old ribbon and the little caps which hold them in. Someone is 3D printing a replacement. There is also a repairer who had some made but, offers them only as part of his repair service as they are fiddly to do - as I have found out - especially when you have lost one of the pins.

I do have an Alphacom and it works great it is even possible to still get paper - if anyone wants just a roll or two let me know as they have to be bought in boxes of 20...

Yes, once you've captured the (Epson etc.) standard data into a print file on a PC etc. then could just process it to display on screen and send this to a standard Windows printer-driver. Like with HPGL file viewer-printers.
And could no doubt also do it on an RPi - maybe running Linux, for a better range of USB Printer support.

I'll have to check out my ZX printer sometime - I do recall the metal stylus, and there being two that scanned the paper like a VCR head-drum.
I'm not sure how long they were meant to last, and I think you could get spares back then (Somewhere, I have an old CPC Computer parts brochure, that listed virtually every part in all the Sinclair computers, including screws).
No doubt the belt has gone bad by now (hopefully not to gooey-mess , like old Philips N1500 ones did).
- I have just looked at all the QL / BT Merlin Tonto (ICL OPD) Microdrive cartridges, and despite the pressure pads looking OK, they fall apart at the slightest prod due to foam-rot. (Audio cassette ones seem to have fared much better, with my 80's tapes still appearing to be OK.

I may also have an Alphacom-32 around. I did borrow & use one back in the 80's, but I ended-up buying a full-width Brother HR5, that could also take a thermal-transfer ribbon as well as thermal paper rolls. But did have to make a Centronics interface for the Spectrum.
Thermal paper seems to be more widely-used than ever, with many till receipts (so not good for long guarantees) and labels (particularly those on packages bought from China etc - that start to go a bit blackened, if you try to use a fan-heater to soften adhesive to remove them intact)
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Old 13th Mar 2021, 8:12 pm   #40
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there hasn't been much coverage of ZX81's 40th
Oh, I don't know, though. Here's a little Youtube piece by our very own Timbucus:-

https://www.youtube.com/watch?v=05eR5zWI0GA

And another one by RetroGamesCollector, whose love for the little black wedge is very evident. There doesn't seem to be a version or variant he does not have in his collection.

https://www.youtube.com/watch?v=QYnMk1X8uio

Those are just two, search 'ZX81 40th' on Youtube.
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