KnightKit Broadcaster Hum

[Mike]

Kind of a shot in the dark with this small group….Trying to get my Broadcaster kit restored….Recapped the power supply, replaced the stinky selenium rectifier with a diode, and installed a polarized power cord just in case of a failure a a hot chassis…..

Getting what sounds like AC hum on the RF signal.  If I isolate the 12ax7 input to the 50C5 PA/Modulator tube the noise goes away.   Do I need more filtering on the 12ax7 plate supply or is this hum a bigger challenge???

thanks

mike. n0mpm

Broadcast Built in 1962 (10 years old)

[Cyber Ship]

Hi Mike,  

For the filter cap(s) did you choose types advertised as 'low esr'?  local CHRS email chat thinks that's pretty important!

Got any other knight's rom the era?

-Bob in 95682

https://californiahistoricalradio.com/

[Mike]

Thaks Bob..I am pretty sure the caps I used were standard ESR....will look into replacing with low ESR and see what happens...

I have my Star Roamer restored and in pretty good shape.   I also have my 12 in 1 kit...it's not in the best shape.  Missing the photo-resistor and the metal guard over the power supply/tube section.  Used to have an Ocean Hopper, but years ago I gave it to a young guy that was interested in radio.  

I have a Knight Crystal Set that is built on a board.  I didn't build it as it most likely from the 1940's era.  

Will let you know if the caps improve my Broadcaster.   FYI, the call letters I made up for my AM radio station was KRBAA (Knight Radio Broadcaster And Amplifier)  That's about as innovative as a 10 year old could get!

Thanks again,

MIke