08-03-2017, 03:43 PM
Off/on switch came in the other day. Mounted it to a small piece on brass and soldered it to the PB assy. Works dandy.
When I was working on it before I didn't notice that the volume and tone controls didn't do what they are supposed to do. Volume control would raise and lower the volume some but it also changed the tone some what. The tone control did very little. Started looking the vol and tone circuit to see if I miss wired something when I was cleaning the pots. That circuit will make you dizzy trying to follow it around. Everything looks OK. After some head scratching I figured it out. The volume control gets it's ground connection thru the secondary of the output transformer (feedback loop) I had left it disconnected till I was ready to get the proper phrasing set up. Checked phase it was backwards fixed that and with loop connected the volume control and tone are back working.
Not real happy with the set up as is. The loop really drops the output down. I'm waiting on some tubes to come in, the 37's were pretty weak so maybe replacing them will help. Did use an external audio source to supply a signal to it and had to drive it w/ a fair amount of audio to get a fairly loud output from the spkr. May revisit the tap arrangement the opt.
Was listening to it on the BCB and noticed at the low end the sensitivity was poor and was getting some images. Could be a tracking issue. Thought it was a good time set the oscillator. Couldn't hear the local 560kc station. Turned it off and went to grab a small screw driver / check the service info for which screws to dittle with. Turned it back on and no reception. Audio is working and I used my little counter to check the lo it's ok so either the mixer or IF has taken a powder.
Going to take a break till the tubes get here, a few days and start troubleshoot again.
When I was working on it before I didn't notice that the volume and tone controls didn't do what they are supposed to do. Volume control would raise and lower the volume some but it also changed the tone some what. The tone control did very little. Started looking the vol and tone circuit to see if I miss wired something when I was cleaning the pots. That circuit will make you dizzy trying to follow it around. Everything looks OK. After some head scratching I figured it out. The volume control gets it's ground connection thru the secondary of the output transformer (feedback loop) I had left it disconnected till I was ready to get the proper phrasing set up. Checked phase it was backwards fixed that and with loop connected the volume control and tone are back working.
Not real happy with the set up as is. The loop really drops the output down. I'm waiting on some tubes to come in, the 37's were pretty weak so maybe replacing them will help. Did use an external audio source to supply a signal to it and had to drive it w/ a fair amount of audio to get a fairly loud output from the spkr. May revisit the tap arrangement the opt.
Was listening to it on the BCB and noticed at the low end the sensitivity was poor and was getting some images. Could be a tracking issue. Thought it was a good time set the oscillator. Couldn't hear the local 560kc station. Turned it off and went to grab a small screw driver / check the service info for which screws to dittle with. Turned it back on and no reception. Audio is working and I used my little counter to check the lo it's ok so either the mixer or IF has taken a powder.
Going to take a break till the tubes get here, a few days and start troubleshoot again.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
