01-23-2015, 03:54 PM
Well, it's alive. Sort of.
[Image: http://www.philcoradio.com/images/phorum...88_043.jpg]
It turns out that the audio output transformer from the 53-960 parts chassis I have was a closer match than the transformer from the 46-1226 (12K input impedance vs. 9K; the original was 12K), so I used the 53-960 transformer after testing and confirming that it was OK.
I then had to borrow a speaker from my (as yet unrestored) 41-788. I have an original speaker for this 42-788, but the cone is destroyed.
So...
I hooked up the 41-788 speaker, crossed my fingers, and fired up the 42-788...
Soon, it was producing the typical buzzing and static heard on the AM band.
Only...no AM signals...not even my SSTRAN!
SW 1 likewise appears to be dead; it has the static and buzzing but is picking up no signals.
I'm not sure about SW 2 as it is not yet evening, but it appears to be picking up some faint signals.
SW 3 is fine; I had no trouble picking up some activity on the 19m band.
I turned the band switch to all of the positions but did not try tuning the spread bands on the right side of the dial as I have not yet installed the needed rubber coupler between the tuning shaft and the shaft which runs the permeability tuner for those five spread bands.
At least I know the set has some life and does not appear to be miswired in any way. Whew!
So now comes the troubleshooting. I tested all of the tubes; the triode section of the 7J7 triode-heptode 1st detector tested slightly weak. I am wondering if it is enough to kill the oscillator on AM, or if I am looking at a coil issue? I would prefer it to be the former, but Murphy's Law being what it is, I wouldn't be surprised if it is the latter.
[Image: http://www.philcoradio.com/images/phorum...88_043.jpg]
It turns out that the audio output transformer from the 53-960 parts chassis I have was a closer match than the transformer from the 46-1226 (12K input impedance vs. 9K; the original was 12K), so I used the 53-960 transformer after testing and confirming that it was OK.
I then had to borrow a speaker from my (as yet unrestored) 41-788. I have an original speaker for this 42-788, but the cone is destroyed.
So...
I hooked up the 41-788 speaker, crossed my fingers, and fired up the 42-788...
Soon, it was producing the typical buzzing and static heard on the AM band.
Only...no AM signals...not even my SSTRAN!
SW 1 likewise appears to be dead; it has the static and buzzing but is picking up no signals.
I'm not sure about SW 2 as it is not yet evening, but it appears to be picking up some faint signals.
SW 3 is fine; I had no trouble picking up some activity on the 19m band.
I turned the band switch to all of the positions but did not try tuning the spread bands on the right side of the dial as I have not yet installed the needed rubber coupler between the tuning shaft and the shaft which runs the permeability tuner for those five spread bands.
At least I know the set has some life and does not appear to be miswired in any way. Whew!
So now comes the troubleshooting. I tested all of the tubes; the triode section of the 7J7 triode-heptode 1st detector tested slightly weak. I am wondering if it is enough to kill the oscillator on AM, or if I am looking at a coil issue? I would prefer it to be the former, but Murphy's Law being what it is, I wouldn't be surprised if it is the latter.
--
Ron Ramirez
Ferdinand IN
