UK's National Computer Museum Looks For Help Repairing BBC Micros 66
tresho writes: 1981-era 8-bit BBC Micro computers and peripherals are displayed in a special interactive exhibit at the UK's National Museum of Computing designed to give modern students a taste of programming a vintage machine. Now, the museum is asking for help maintaining them. "We want to find out whether people have got skills out there that can keep the cluster alive as long as we can," said Chris Monk, learning coordinator at the organization.
"Owen Grover, a volunteer at the museum who currently helps maintain the cluster of BBC Micro machines, said they held up well despite being more than 30 years old. The BBC Micro was 'pretty robust,' he said, because it was designed to be used in classrooms. This meant that refurbishing machines for use in the hands-on exhibit was usually fairly straightforward. 'The main problem we need to sort out is the power supply,' he said. 'There are two capacitors that dry out and if we do not replace them they tend to explode and stink the place out. So we change them as a matter of course.'"
"Owen Grover, a volunteer at the museum who currently helps maintain the cluster of BBC Micro machines, said they held up well despite being more than 30 years old. The BBC Micro was 'pretty robust,' he said, because it was designed to be used in classrooms. This meant that refurbishing machines for use in the hands-on exhibit was usually fairly straightforward. 'The main problem we need to sort out is the power supply,' he said. 'There are two capacitors that dry out and if we do not replace them they tend to explode and stink the place out. So we change them as a matter of course.'"
Ah That's Good Shit (Score:4, Interesting)
For my hardware class, I brought it in, took it apart and handed the chips around the class. At the end, I reassembled the whole thing and booted it back up. Fun little presentation. That old hardware could really stand up to a lot of abuse.
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This was in the early 90's, just before the 286 really started to catch on.
I think your dates may be a bit out. By the early 90s the 286 was vintage.
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Replacing capacitors... (Score:1)
... is childs play to anyone with a decent soldering iron, solder wick, flux, and one of those spring loaded vacuum solder suckers to clean out the hole (and a little practice!).
Here's how I do it:
Melt one lead of the capacitor at a time, pulling (axial) or wiggling (radial) the capacitor from each side. Sometimes if it's really uncooperative (usually if capacitor is in a bad place to get at) you might try solder wick with flux on it, and try to suck out the solder that way.
Once the capacitor is out, check
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Great way to pull the plating out of vias. Way to go, genius. You're bush league.
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Power supply circuit boards of that vintage, and even some of them today, are usually single-sided without plated through vias to pull out.
Not sure if you knew this, or if you're sorta bush league yourself.
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Bit of both with the BBC micro. The main board is double sided with vias. But the PSU board is single sided. And we appear do appear to be talking about the PSU.
Still, the other poster made a worthwhile cautionary note for the general case. All be it in an unnecessarily obnoxious way.
Some info on replacing the caps here:
http://www.retro-kit.co.uk/pag... [retro-kit.co.uk]
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Yes. Jumper wires are usually the best method. Connected from a component terminal to component terminal. Best to not put a lot of effort into 'repairing' the original trace. An obvious well anchored jumper wire is better than a little bit of bare wire 'woven' into the trace. There are ''quality standards' for that form of rework.
Back when I was troubleshooting medical device circuit boards that were fallout on a production line, I would sometimes find attempts by operators to 'fake out' the rework whe
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The trick is add more fresh solder to the joint (thus adding more flux and melting the entire joint on both sides) and then use the vacuum plunger tool to suck everything out. All the solder will flow together and magically disappear into the vacuum tool.
All the boards from that era were hand stuffed, and sometimes they u
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First, always use a soldering iron with a grounded tip. Wipe it on a wet sponge, apply some new solder to the tip, and shake any excess off the tip. Now you'll get good heat transfer.
Looks like we've uncovered a hidden reserve of soldering weenie waving.
Reading down these posts reminds me of a soldering class I was teaching last year. An onlooker decided to take me to task over every single thing I was teaching. It was like heckling a comedian. Unlike a comedian, or a big dick soldering guru, I decided I'd give the fellow some rope. So I invited him up. He proceeded to go on a rant about the solder sponge want the right amount of water, the iron was too hot, it wasn't tinned correctl
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Sorry, didn't think I was dick-waving.
You actually weren't, so I need to do the apologizing. Your post was just the one where I joined in, after my solder class memory was triggered. You are quite right, I use a smidge of solder added for the same reasons, vaccing or solder wicking and also to get more effective heat transfer.
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Solder wick has a lot of uses, though. It's more useful for medium-pitch surface mount rework, where you're trying to remove as much of the solder off the tiny pins. Once you have the solder wicked out of the fillets, the terminals can be popped loose one at a time. I used to pride myself on being able to remove an SO-8 package and be able to put it back on.
For through-hole rework a spring loaded solder sucker is better, or if you're wealthy or for professional work, a powered desoldering tool with a vac
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Actually, that's not as silly as it sounds. IIRC the Beeb's PSU produces fairly standard 5V and maybe 12V and the machine doesn't draw all that much power. I would have thought it would be quite easy to find a standard PSU of appropriate spec that could be substituted.
Comment removed (Score:3)
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Yes, and replace them with modern power supplies before they fail. Power supplies rarely fail in a clean manner, which is to say that they will still provide power even if it is not functioning properly. The voltage may be too high or too low or, in the case of dried out capacitors, fluctuate. In most cases the computer will behave irratically, yet there are also cases where it can end up damaging other components. So just take the preemptive measure of replacing the power supplies to ensure that the cr
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...replace them with modern power supplies before they fail.
That's fine if you just want to keep the machines functional, but this is a Museum and restoring this as close to original condition as possible is the goal.
I do not believe that modern power supplies are any more reliable in the longer term, given the number I have seen fail. These machines have lasted 30 years on the original PSUs. The goal is to keep them going another 30 years and beyond, not just get them up and running for now.
It sounds like they know at least some of the key problems. What they need
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This is for a cluster that is being used not an exhibit in a glass box.
I think modifying the existing power supplies is probably the best way to go today. Replace the caps and possibly the voltage regulators with newer parts might be a really good way to go today.
I would suggest starting a project to create a modern PS that could be a drop in replacement for the old one. It could use a lot less power and be more reliable in the long run.
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The BBC Micro switching power supply design includes cycle-by-cycle current limiting in the primary side of about 2 amps and an SCR crowbar on the +5 volt output so they are going to fail cleaner than most power supplies. From browsing various discussions it looks like most failures are the paper X and Y capacitors and the aluminum electrolytic capacitors. I am surprised they cannot find someone familiar enough with switching power supply design to refurbish and improve them.
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This is the UK, where they'll find more engineers with experience fixing BBC Micros than C64s.
They'll certainly get some education support people that maintained BBC Micros for Local Education Authorities. And they may well even get some ex-Acorn engineers - some of them will be retired now, and would be happy to help a museum out preserving something they love.
BTW, one of the neat things about the BBC Micro is that they shipped with a complete circuit diagram for the main board in the back of the manual.
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BTW, one of the neat things about the BBC Micro is that they shipped with a complete circuit diagram for the main board in the back of the manual.
They provide a small but complete schematic of the C64 in the back of the thick ring-bound manual that came with that system, too.
For that matter, you could buy Technical Reference manuals for the IBM-PC product lines and many of us have them. It has schematics of the mainboard and all the IBM-brand expansion boards, along with commented source code listings for
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Acorn used to supply a circuit diagram and fairly good reference docs for the BBC.
Virtulize it (Score:1)
It would IMO to be easier to virtulize the OS if they want to demonstrate it. They could even give away the VM so people could fiddle at home.
Re:Virtulize it (Score:5, Insightful)
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I quite fancy the idea of programming a game for the BBC micro. I've learned so much since those days, it'd be fun to see what could be done with such a limited machine.
However, I'd want a modern text editor and git. I wouldn't want to go back to using cassette tapes or even 80KB or whatever they were disks.
I guess that probably means using an emulator, at least for the development part. With the odd check that it does work on a real machine.
There's probably a web site about this...
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Yes, and they could copy the Mona Lisa so everyone could see it up close.
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They have. You can see it here:
https://upload.wikimedia.org/w... [wikimedia.org]
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I have a BBC emulator and it's good. It truly isn't the same thing as using the real hardware though - even simple stuff like the feel of the keyboard. I have vice64 and use it to emulator the C64, but I also have a real C64 sat in my retro-cupboard all set up and ready to go. That cupboard contains a monitor/TV, C64 with 1541
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IO ports. The Beeb had millions of them
The are a good modern alternative (and cheaper than a BBC was, back in the day!). The LPC1768 has the same amount of RAM as the BBC and a bit more flash than the BBC had space on a floppy disk, and has analogue and digital I/O pins, as well as serial (which the BBC had with RS-423), and a few things the BBC lacked (Ethernet and USB). [mbed.org]
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Seems like one could make a cape for BeagleBoard or an add on for Rpi with the IO and an emulator for the BBCMicro.
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Emulators can be useful in many ways, but they can not replace the real thing.
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Boooooooooo... (Score:1, Redundant)
...beep.
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Damn, just when my points expired.
Loved that machine, and can still hear that boot-up sound.
Pity the 64 beat it hands-down on graphics - the BBC was way more advanced on the OS side, and the built in BASIC was actually a decent structured language you could do real stuff in.
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Being an oik I only had a Sinclair Spectrum. One of the posher kids had a BBC and IIRC you could even inline assembler inside a BASIC program.
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virtualization (Score:2)
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And how do you plan on plugging in and interfacing all the 1980s peripherals to a 2015 PC exactly?
I'll do it... (Score:1)
I could do this, I used to be a Commodore Service. (Score:4, Interesting)
I can read from the various posts in this thread that you all think it's a walk in the park to fix these old 80's computers, oh boy...you guys may know a couple of common things such as dry soldering and drying capacitors, but there's a lot more to fixing those things than you might know.
One of the most common faults of the 80's was the ROM/RAM circuits, they where often clusters of 2/4/8 kilobyte ram chips (often 4164 etc.), and finding dead ones requires a couple of "old skool tech skills", one of the simplest one is the "thumb test", is one of the Ram chips very hot (you could of course use a bottle of cold-spray, I don't know what it's called in your country...but to us it was just Cold spray, this is essentially a spray that sprays super cool air because of a chemical process when in comes in contact with air, the surface will be really cold, forming ice crystals) and then you can see clearly which surface is getting hot fast. Another method is to use the oscilloscope to see if anything is out of the ordinary (you need to know how it looks as an image first, the voltage changes because of the logic communication will form an image, and if you know how it looks when normal, this is also a method we used.)
You can also use a logic tester, this is an instrument that can monitor the traffic in those logic circuits, you can set it to the speed of the actual logic (usually 1 to 20 MHz, depending on the computers speed) and see if everything is okay.
Another common flaw back then, was broken prints...over some time, these boards gets really hot, and this stretches the metal on the PCBs, and broken connections is some of the hardest things to find.
Another typical flaw is design flaw, over time...we needed to change I/O chips on certain models simply because it was so badly designed that they would eventually go bust, they where very sensitive too...so many of the DIY'ers out there who made their own Fast-Loaders/Robotics connected to the I/O ports would regularly blow these chips.
Pity I live in Scandinavia, I'd love to retire doing this
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You can look up the details but the early BBC MIcro power supplies were linear and the later ones were off-line switching power supplies.
ATX power supply (Score:2)
I just replaced a fried power supply from a 30 years old 8 bit computer. I used a modern ATX power supply and it works fine.
As noted earlier, the only problem is the missing -5V line, which existed in AT power supplies but was removed in ATX. But many ATX power supplies still offer the -5V line through the "reserved" pin 20 (it faces the grey wire "power good" on pin 8). If there is a white wire there, you have it.