I just wanted to share my experiences of fixing a power supply problem with a Beocom 4.  Other posts suggest that this may be quite common. 

My Beocom 4 developed an intermittent power supply problem that I eventually traced to the connection between the charging cable and the plug in charger.  I initially thought the cable had a break in it, hence got a quote for a replacement charger - £35!

Whilst trying to take the charger apart, I realised that by twisting the cable/charger connection by 90 degrees it actually detaches from the charger to reveal that it is connected with a standard DC plug connection - like the one used for mobiles.  I undid the single screw under the charger and used a bit of brute force to pull it apart.  Upon pulling out the small circuit board it was immediately apparent that the surface mounted DC socket solder joints were dry/disconnected.  Ten minutes with the soldering iron, reassembly, and all is now working perfectly.

Hope this is useful!