Anyone else going to "Fix a Beeb day" at National Museum of Computing?

[Peter Parker]

In response to "Computer museum seeks BBC Micro fixers" on the BBC News site at the end of June, I emailed them and heard nothing ... until a couple of weeks ago when I was invited to an event tomorrow (Sunday).

So I'm taking my screwdriver set and an old BBC Model B circuit diagram to Bletchley Park tomorrow and just wondered if anyone else was going. I'll try and take some photos if anyone's feeling old and nostalgic.

[Rob_B]

Definitely sounds interesting, get some pics up when you get back
There is much love for Bletchley on here and funnily enough tonight I just watched The Imitation Game.

[TheAnimus]

Haha that takes me back. I remember when overclocking involved a new crystal!

Good luck and I hope it's a fun day.

[Peter Parker]

Brief follow up for anyone interested :-

http://www.tnmoc.org/news/news-relea...eeb-fix-it-day
http://blog.coyoteproductions.co.uk/...en-bbc-micros/

Proud to say that one of the 36 Beebs fixed was my work

I arrived at Bletchley station just before 10am and happened to meet an official museum volunteer on the short walk up to TNMOC. Over the next 30 minutes more of us arrived and we got the coffee machine going and started find out from Owen what we were supposed to do.

The main problem with these computers are that the capacitors in the power supplies fail after a few decades. So every single machine we fixed had a standard PSU refurb procedure: open up the built in PSU (warning 240V electricity, risk of death if you try this yourself etc.), then de-solder, remove and replace two film capacitors and an electrolytic capacitor. A supply of the right sort of capacitors was provided on the day, and we managed to use up all of them! I've a degree in electrical and electronic engineering, so I'm not put off by a bit of soldering, but ... the machines are solidly built. Figuring out what to unscrew, how to click out the various grommets and remove cable ties, and how to trace the solder leads on the other side of the PSU PCB was time consuming even with a service manual. The write up in the articles also neglects to mention the muted (kids were present) cursing and muttering going on as we tried to crack open these beasts! Fortunately several people there were from the Stardot Beeb group and had experience doing this, which was a huge help.

After that, in the ideal world you re-assemble the Beeb, flip the power button on the back, and get the satisfying booo-BEEP two tones indicating it's booted up. For some of us unlucky people though, you just get booooooooo.... The first "booo" tone indicates the 6502 CPU has started and managed to initialise the sound enough to play a tone. The second BEEP is means that the OS and BASIC ROMs have finished loading. Lack of second tone meant one of the many socketed chips probably needed replacing, or even a damaged main PCB. Much random swapping of chips is needed to try and figure out if a ROM/EPROM is damaged, or a 3rd party expansion board is broken. Near the end of the day I worked out that one of the two 6522 VIA chips was faulty in the machine I was working on, and after hours of frustration I finally swapped it for a working chip and got the second beep. I did a little dance.

The satisfaction of getting these machines up and running again is a wonderful feeling for someone who grew up and learned to code with them. I had a great day at TNMOC and recommend going to have a look around the various old machines, like the Colossus rebuild, or the metre-wide 5MB disk platter . Great day and would gladly do it again!