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My Collins KWM-2 uses a home brew power supply. Step start on filaments -
at correct voltage and no high voltage for 60 seconds. Same tubes in it for 30 years. I think the only two power amplifier tubes that failed were dropped on the floor. Some amplifiers adjusted the filament voltage to be correct and some were never measured. I ran a 3 x 813 amp for years and never changed the tubes or even measured the filament voltage. Just used a transformer with the rated voltage and called it good. Unless the filament transformer has a current rating much higher than the demands of the amplifier tubes, the surge will probably be ok. Incidently, the home brew equipment looks practical. I built a vfo using the Collins 70H3. The problem with it is that it covers 1.5 to 3 MHz with 10 turns. That is 150 kHz per turn. Bad for a linear dial. I used a 8:1 reduction gear and a crystal controlled mixer to cover 5 to 6.5 MHz, then limited use to 5 - 5.5 MHz. That was coupled in as the second vfo for my Drake TR-5, so when I switch it in, the Drake digital dial displays the frequency. Extremely stable. Oh, I converted it to solid state, also, which is easy to do. There is one minor problem in that there are no stops on the dial. Not a problem for me, but if some kid came in and started twisting, he could break something. Oh well, you need to take some risks in life. 73, Colin K7FM |
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