IR remote volume controller (July 1996), Pro Series 4 preamp (December 1996):
Depending up the brand of 74HC132 chip used in the IR transmitter unit, it may
not be possible to adjust the oscillator to the required 38kHz using RV1 (1k).
If this seems to be the case, try replacing RV1 with a 10k trimpot or perhaps
changing R1 to 6.8k - many thanks to Norm Vella for pointing out this problem.