Although there are several resources on the web (1, 2, 3, 4) on how to convert a RR501 transceiver from 110v to 220v I recently (mid 2010) bought a new one that had an updated circuit. As shown on the following pictures the board says 10432I on the case says 07J40.

Using Ido Bartana's guide as a base and these general tutorials on 220v module modification (1, 2) I ended with this set of steps

• Change the large blue, (C28) from 1uF/250V to 470nf/400V
• Change the smaller blue, (C29) located close to the output connector, from 0.22uF/250V to 0.1uF/400V
• Change the 130V MOV in parallel with the input to 250V RMS
• Change the 130V MOV in series with the relay to 250V RMS
• Add a 100 Ohm/1W resistor in series with the 110v cam relay coil

The mod mentioned above only lasted a coupe of months. Here is the 2nd attempt I did with a new module

• Change the large blue, (C28) from 1uF/250V to 470nf/400v
• Change the smaller blue, (C29) located close to the output connector, from 0.22uF/250V to 0.1uF/400V
• Change the 130V MOV (R47) in parallel with the input to 250V RMS
• Change the 130V MOV (R48) in series with the relay to 250V RMS
• Change the 220k 1/4W resistor (R21) going to the output connector, to 470k 1/2W
• Add a 100 Ohm/1W resistor in series with the 110v cam relay coil

The result looks like this