I have recently repaired one of these radios. The fault was a literally burnt out audio chip that had turned to black carbon. The chip is inside a can and would be very difficult to unsolder if it had not vaporised! The next problem would be actually getting a new audio chip (TPA2005). Looking on the internet I came across this 5V 3W stereo amplifier for 99p including postage! (see picture).
I made sure I broke all connections to the original chip and fitted this one. The supply to the chip was reduced by putting a 1N4001 in series with the supply to limit the voltage to around 5V. On switch on the radio works perfectly with good volume. I was only using one side of the amplifier.
The input on the original circuit is stereo enabled so my next step is to find an identical loudspeaker and remove the battery compartment and fit the LS on the other side and end up with a stereo RD60!
I used one of these little PCB’s recently to fit some small speakers into my workshop PC monitor, there was just enough room in the case to fit the speakers facing out the rear ventilation slots, and I managed to find a suitable 5v supply in the monitor to tap into.
I like the idea of making the RD60 stereo! I have an RD50 here, which I recovered in dark denim as the original fake leather had decomposed into a right mess! Nice radios other than that.