BC348 , BC348 World war 2 receiver , B17 Radio , Bc348 Update скачать в хорошем качестве

BC348 , BC348 World war 2 receiver , B17 Radio , Bc348 Update

My BC348 receiver designed during World War 2 developed a problem when it was tipped back it buzzed loudly something was shorting out ! This video is an update on this receiver the first video on the BC348 I made several years ago . What I eventually found was a loose screw rattling around in the power supply shorting out the B+ filter capacitor . While I had it apart I checked all tubes with a emissions type tube tester and found the audio output tube had very low emission even though it worked that tube was replaced . The power supply I made back in 1972 and I did not want to re-wire all the tube filaments I managed to find a small transformer about 1 amp at 24 volts and used that for the filament power.this was a lot easier to do than rewiring all the tube filament wiring . I recommend doing this the transformer I used was actually a 48 volts center tapped one I just connected one side of that center tapped winding it has worked fine now for many years and the transformer runs cool so I guess it is ok . The 180 Ohm resistor I had installed I then changed to a 120 ohm resistor the - 8 volt bias voltage came up quite a bit to around 15 volts with the new 6K6 tube installed which necessitated changing that resistor to a lower value . You will notice in the video a wire with a two pin molex connector on it this plugs into another molex connector for the 120 volt ac input . Another thing I changed some time ago was installing a new three prong power cord for safety with the green wire grounded to the BC348 chassis . The B+ measures 210 volts on this 348 and the filament 24V ac . After installing the new 6K6 audio tube I noticed the audio was a lot louder and clearer also that -8 volts bias does move around a bit according to the strength of the received signals and the setting of the volume and RF gain controls . These videos I make to share and preserve ideas and procedures with others interested in electronics or Ham radio . 73 Happy Holidays Bob