BBC Model B repair and restoration

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BBC Model B Repair


I love collecting and repairing retro computers, but prices can get high so I usually buy faulty ones and try to fix them.
Recently I picked up a BBC Model B listed as “powers on, light comes on, nothing else working.” That sounded like a potential easy fix, so I made a cheeky low offer and it was accepted!
In this post, I’ll walk through how I diagnosed and repaired the fault.
Unfortunately, my camera corrupted most of the footage but I managed to save some photos from the process and the final video of it powered up and working.

Please note that this is a hobby for me and you should not do this if you do not know what you are doing as you could risk electrocution!!!


First off opening up the case, there was no obvious damage, which is a good sign.



These computers are now over 40 years old, and the electrolytic capacitors in the PSU tend to dry out or leak, causing start-up failures or blown components.
Since the previous owned powered this on, no doubt one of these failed.
So next to get the power supply out of the case.

First I took photos of the power connections and then removed them from the main board.


Then I removed the screws from the back of the case holding the power supply unit in place.


Then removed the case and examined the power supply unit

Sure enough one of the capacitors had exploded.
After removing the power supply board from the housing, it was easier to see the blown capacitor in the bottom left corner of the photo below, between the transformer and the heatsink.

Rather than just replace the one capacitor, it makes more sense to replace all the electrolyte capacitors seen.


First I removed all the capacitors using a de-soldering tool and de-soldering wick as shown above.

I then resoldered the new capacitors in place, holding them in place with blu-tac to ensure they didn't fall out or move out of place before soldering.

The final result can be seen above.
I then put the power supply unit back together and powered up the unit on its own and no issues.
Then I put the unit back into the case and re-connected all the leads, the speaker and the keyboard. I connected the BBC to my tv and powered it on and all worked.
I managed to save the video for this at the end and can be seen below.


All that is left to do is to clean up all the dirt around the inside of the case and on the main board.

Hopefully in future I can show more retro-console repairs and show more videos of the different process. Currently I have a spare C64 awaiting repair, which hopefully I can document soon.


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