Homebrew Vactrols

[Mike I.]

I have an old Morley Pro-Phaser. This is a 6-stager  using LDR's 
surrounding a #327 pilot lamp. The LDR's have a nearly black sensitive 
surface - I have not seen this type before, perhaps it is CdSe? These 
LDR's seem fairly sensitive - at the moderately-wide sweep I like best, 
the bulb glows reddish-yellow when it is brightest, but still puts out 
less light than an old-fashioned GaP red LED. The bulb is rated for 28 
volts, but does not show any darkening of the glass even though it was 
built in 1976 (presumably it is being operated well below maximum 
ratings). I built a phaser with a large high-brightness orange LED once 
(for illuminating the red-brown CdS LDR's), but found that a normal red 
diffused LED worked adequately. Mike