One of the drawbacks on the Reslytone is, if the indicator light burns out (which is likely) a ready replacement is not available. This is easily replaced with an LED which can be run by a simple mod board which replaces the original sub board. (click on the image for the full size schematic). To see this in the context of the whole circuit click here:

Seen here is the new board with a simple Darlington pair of BC547s running the indicator LED through a 3K3 resistor. The input Z is very high at around 500K, and is much more efficient, and better centred (brightness and darkness) compared to the old incandescent bulb setup. The board is easily wired up to the original connections, so that originality can be restored at any time. I used the original jewel light housing and fixed the LED with epoxy. Once replaced, you'll never have to bother with a new light again. The LDRs (in the metal box) are also fed by small bulbs but they seem to last OK.