Rhodes 73 MK1 Satellite Tremolo

[soulof70]

Hi,
I have a Rhodes 73 MK1 Satellite, but without the satellite speakers. I use a CAE Sound Preamp model RSPS1 to connect to a conventional amplifier.
Recently the stereo tremolo stopped working. It has not stopped me using the piano as the sound only disappears when I switch on the tremolo.

I've checked the lamps and they both light up when the tremolo rotary switch is pushed in (tremolo off), but when I pull it out (tremolo on) they both go off. This is when I guess they should be lighting up alternately??

So it's obviously one of the components in the chain, but I have no idea how to check any components other than resisters and continuity. Could it be one of the 3 legged transistors?? ...and how would I test them or know which ones might be suspect.

My electronics knowledge is basic, but I can replace components and do very basic fault finding.

Thanks in advance,

Scott.