12-25-2013, 02:34 PM
Radioroslyn;
Thanks for the compliments! Yes a nice BFO would be nice for alternate modulation type signals. I might do something along those lines. I have a few single gang variable air capacitors that I could use to create something for that purpose.
I discovered a minor problem earlier today. If I had the volume set at a certain level, and turned the tone control from end to end it killed the sound completely at anything past 1/2 way toward the plate circuit of the 1st. audio tube. It was not the control, verified with power off and using the ohm meter. It turned out to be another one of the .01mFd capacitors that had shorted (part item 52) which someone had installed years ago. It should have been a .006mFd in order for the tone control to work properly. I was out of .01 capacitors but had a few that I had removed from the set. I found two that were not shorted or leaky and put them in series which makes a .005mFd. I also had a 1000pFd silver mica capacitor and added that across the two in series to make a .006mFd. I took the offending shorted capacitor out of the set and installed the cludged capacitor in its place. I turned the radio back on and Presto! No more loss of audio as the tone control is turned end to end. An added plus is that it also now really does change the tone like it should.
I notice an odd popping sound as the set is warming up. It may be due to one of the audio tubes, but it goes away after the sound comes up and does not return until I turn it on from a cold start again. I hope it is not some problem developing with the field core of the speaker.
The radio sounds so good right now that I may just let it go until I find it becomes a real problem that is obvious to find. I might monitor the B+ to see if there is any fluctuation there as the radio is warming up from a cold start. That would probably show up easiest at C77 if there is an intermittent short or open happening during warm-up.
I went ahead and installed the new push-buttons on the front that I had ordered. They were loose and popped off when pushing adjacent push-buttons, so single folded layer of Scotch magic tape over the button shaft was enough material added to make the push-buttons stay on their shafts.
Joe
KC5LY
Thanks for the compliments! Yes a nice BFO would be nice for alternate modulation type signals. I might do something along those lines. I have a few single gang variable air capacitors that I could use to create something for that purpose.
I discovered a minor problem earlier today. If I had the volume set at a certain level, and turned the tone control from end to end it killed the sound completely at anything past 1/2 way toward the plate circuit of the 1st. audio tube. It was not the control, verified with power off and using the ohm meter. It turned out to be another one of the .01mFd capacitors that had shorted (part item 52) which someone had installed years ago. It should have been a .006mFd in order for the tone control to work properly. I was out of .01 capacitors but had a few that I had removed from the set. I found two that were not shorted or leaky and put them in series which makes a .005mFd. I also had a 1000pFd silver mica capacitor and added that across the two in series to make a .006mFd. I took the offending shorted capacitor out of the set and installed the cludged capacitor in its place. I turned the radio back on and Presto! No more loss of audio as the tone control is turned end to end. An added plus is that it also now really does change the tone like it should.
I notice an odd popping sound as the set is warming up. It may be due to one of the audio tubes, but it goes away after the sound comes up and does not return until I turn it on from a cold start again. I hope it is not some problem developing with the field core of the speaker.
The radio sounds so good right now that I may just let it go until I find it becomes a real problem that is obvious to find. I might monitor the B+ to see if there is any fluctuation there as the radio is warming up from a cold start. That would probably show up easiest at C77 if there is an intermittent short or open happening during warm-up.
I went ahead and installed the new push-buttons on the front that I had ordered. They were loose and popped off when pushing adjacent push-buttons, so single folded layer of Scotch magic tape over the button shaft was enough material added to make the push-buttons stay on their shafts.
Joe
KC5LY
