A very common problem with the BBC computers is the failure of one or more smoothing capacitors in the power supply.
If you have turned on an old BBC computer which shortly afterwards gives out a "popping" and "crackling" sound, followed by your room being filled with foul smelling, acrid smoke, then this is your problem.
If you remove the power supply and send it to me, then I will replace these capacitors, and replace the "start up" capacitor (these also often fail, so the BBC will not start up) test and return the power supply to you. If it cannot be repaired, then there is no charge other than the return postage.
Click on the Shopping Cart button to checkout and pay and post your PSU to me to the address on the "Contact Me" page.