Slashdot Mirror
UK's National Computer Museum Looks For Help Repairing BBC Micros
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.'"
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.
I'm trying to teach myself to set people on fire with my mind... Is it hot in here?
... 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 if you can fit the new capacitor leads through the holes. If not, use a soldering iron on one side to heat, and have a buddy on the other side to use the vacuum tool. Hold the iron on until the solder's melted, and without removing the iron, use the vacuum tool and in one or a couple tries it usually clears it out fine.
Putting the replacement capacitor in is dead simple to anyone that's done through-hole soldering... really if you can't get this skill down first, don't try the previous stuff (practice on some cheap electronics kits).
Main thing to watch for is applying heat for too long to the point that the varnish burns or traces start to lift. But on older boards, it's usually leaded solder so melting temperatures aren't that bad. Just make it a goal to work as quickly as you effectively can once the heat is applied.
There's tons of old motherboards and power supplies and stuff from the Capacitor Plague to practice on.
Again, this isn't the hard part of repairing electronics. The hard part is when the problem isn't capacitors and some actual thinking is needed to locate the problem (and *this* is where domain specific knowledge and tricks can come in!)
I mean, can't you modernize the power supply a little? Just keep a copy of the old power supply on display while having a newer one inside.
Would you repair PBS's stuff? Hell no! What is your fascination with this?
There is a fairly healthy C64 community, including electronic engineers and tinkerers, who have been able to build replacement power supplies for the good ol' breadbox given that it had particularly ugly power supply issues as well.
I don't think it would be too difficult to ask them to take a look at the BBC Micro to see what could be done there....
READY.
PRINT ""+-0
Somebody stop me http://www.dailymotion.com/vid...
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.
...beep.
systemd is Roko's Basilisk.
1) Head over to EEVblog and set up your FREE account.
2) Post high-res pictures of top/bottoms, and angled views for component IDs.
3) Wait for the gurus there to scan, map, and reverse engineer the whole thing.
4) Wait some more, and they'll also provide improved schems, PCBs, and a BOM.
5) Undoubtedly, someone will have the PCB(s) manufactured and sent out to you.
6) Profit? I guess?
Seriously, I've seen more than a few threads there that have done just that (maybe not step 5, but 1-4). More importantly, a lot of those folks are already in the UK (or just a quick trip through the Chunnel to get there), and are brilliant engineers. So, give 'er a go!
virtualization is the solution. if it fails, just make a new copy.
now we need to go OSS in diesel cars
Because those machines are just as old and therefore come with just as dry capacitors?
Nae king! Nae laird! Nae yurrupiean pressedent! We willna be fooled again!
... if you pay to fly me to the UK and back, parts and labour.
Buck Feta. You know what to do.
..technician back in the 80's to 90's.
:)
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
What this world is coming to - is for you and me to decide.
Always discharge a big capacitor before removing them. A big charge left in them could be deadly to you.
Anyone can do it if they can handle a soldering iron. Caps in 80s power supplies are trivial to swap out. What they should be doing is replacing those shitty 80s power boards with modern multi-tap switched mode units that'll work better, last longer, and use less energy. Any remotely competent "tech" can design such a board.
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.