Bench Test of Collins KSW-1 Transmitter Through to Driver Stage 

This Collins KSW-1 transmitter (part of a set of 'Gold Dust Twins') has had all its paper and electrolytic capacitors, and 20 out of tolerance resistors replaced. Prior to this video, I had checked that the PTO and carrier oscillator were working while powering the chassis with a Heathkit PS-4 power supply for the B+ voltage and separate 6.3v and 12.6v heater transformers, However, the Heathkit power supply could not supply the required 140mA B+ current draw at 275vDC, so I was operating it with only 225vDC B+ voltage. As I have not yet refurbished the Collins 428A-1 power supply, I built a 'beefier' bench power supply. With this connected, I decided to sniff around in the mixer and amplifier stages of the transmitter using a small e-field probe connected to a TinySA spectrum analyzer. This video provides a demo of part of the transmitter's RF functionality operating like this (no driver or PA tubes installed).