I live in the Berkeley California
Why? 

If you press TV on your Beolink 1000 and get no response (no sound, no display, no noises of any sort), you probably have a problem with the computer board. It is not allowing the set to turn on. You can try measuring the voltage on the lithium backup battery on the board to see if it's still good or not. If the battery is still good, disconnect the battery for half a day, then plug it back in and then try turning the set on. If this doesn't change the outcome, you can replace all the capacitors on the board, including the ones inside the "can" (metal enclosure). When replacing, use high temp caps (105 degrees C) as they will last longer. If you don't want to do the board repair, Atlantic Systems in Massachusetts still works on these TV's and can set you up with a repaired board for you to swap.

When taking the back cover off, it is easiest to have the tube facing down on the ground. You want to take the proper precautions for working on any TV - high voltages still remain on the connector on the back of the tube with the rubber suction cup. 

Just to say that I am the one who repaired his MX-5000 and it is still working well! However, it is relegated to a be a bed room TV as I now have a BV-7 as my main TV set since two years. 

The problem of not powering up sometimes occurs with the MX-5000 after there has been a power failure. Disconnecting the mains plug and reconnecting it solves it. Also ensure that the batteries of the Beolink 1000 remote are good.

To the original poster: If the capacitors of your MX-5500 has never been replaced before, then be prepared for a major job. All black electrolytic capacitors of Rubycon brand must be replaced on every board. After that, the TV will work as new.

Ask for an estimate from the repair shop before taking the decision. 

Good luck!

Jean

Thanks Matapan and Jean ... these suggestions are very interesting.

I have an MX 3000 I acquired via eBay ... that died after 3 hours of operation.

The local B&O engineers have looked at it and said it can not be repaired as spare parts are not available any more.

However are there alternative approaches for an MX 3000 like the ones you have outlined above?

It depends on the problem you are experiencing with you set.

If the standby light turns on when the set is plugged in, but the set does not turn on (no picture, no sound), and a repeating "fumping" noise, you have a power supply problem. I can't speak for the European sets like the MX-3000, but this sort of problem can usually be repaired by replacing some capacitors on the power supply board. There are high voltages present on this part, even when the set is unplugged - if you have little experience working on sets, it is best to take the set to a servicer. 

By "spare parts", I would request clarification from your local B&O engineers. Do they mean replacement modules or circuit boards? If so, this is probably true - the sets are now about 20 years old. If they mean discrete components on the boards required to fix the set, that's a different case. You could always get another MX-3000 on eBay as a spare parts donor if this is truly the case. I've found most repairs only require the replacement of capacitors though.