02-11-2015, 04:35 PM
I found that I could pick up the local AM station at 990 kc by placing a finger on the grid cap of the 6J8G det-osc tube. I could also pick it up by placing a finger on the grid of the 6K7G RF tube, but with lower volume. One serious problem, though: 990 was coming in around 650 on the dial, and I could not receive my SSTRAN at all (it's tuned to 660 kc).
Knowing the coils had good continuity, I decided to try performing a complete alignment.
The AM alignment was way, way off. I had to go through the procedure on AM several times, adjusting first at 900 and 1400 kc, then 750 and 1400, and finally the factory recommended points of 580 and 1500 kc. It finally lined up as it should.
Here it is, with the dial scale back in place:
[Image: http://www.philcoradio.com/images/phorum...770-59.jpg]
But I am not happy with it. I am no longer receiving the local station at 990 kc (at all). It is picking up on the high end of the band, and picks up my SSTRAN at 660 with plenty of volume, but seems to be deaf in the middle of the band.
The action of the tuning indicator became clear during alignment. Normally, the lamp is lit somewhat dimly. As you tune in to a strong signal, the lamp grows brighter. You tune for the highest brightness on the lamp. Pretty neat.
SW seems to be A-O-K. The highest band, band A (11.6 to 22 mc) seems to be working well with no noticeable issues. Band B (5.5 to 11.6 mc) also seems to be OK. It was too early in the day to really test band C (1.7 to 5.6 mc) although I was picking up a couple signals in the 60m band.
Not sure what to do from here - try probing further, or just let it go and call it good enough.
I really think that part (8), the band C RF coil, has been replaced with an incorrect replacement, and this may be the source of the trouble. The primary of this coil is also used on the AM band. The primary should have a resistance of 80 ohms according to the schematic. This coil doesn't quite match the drawing on the schematic, and its primary has a resistance of 120 ohms. (And maybe this is why the wires of this coil looked like the coil had been removed at some point - maybe it was removed from another Philco set!) I suspect that this may be an AM RF coil from some Philco set.
As always, I'm open to suggestions...a replacement coil is, most likely, unobtainium...
Knowing the coils had good continuity, I decided to try performing a complete alignment.
The AM alignment was way, way off. I had to go through the procedure on AM several times, adjusting first at 900 and 1400 kc, then 750 and 1400, and finally the factory recommended points of 580 and 1500 kc. It finally lined up as it should.
Here it is, with the dial scale back in place:
[Image: http://www.philcoradio.com/images/phorum...770-59.jpg]
But I am not happy with it. I am no longer receiving the local station at 990 kc (at all). It is picking up on the high end of the band, and picks up my SSTRAN at 660 with plenty of volume, but seems to be deaf in the middle of the band.
The action of the tuning indicator became clear during alignment. Normally, the lamp is lit somewhat dimly. As you tune in to a strong signal, the lamp grows brighter. You tune for the highest brightness on the lamp. Pretty neat.
SW seems to be A-O-K. The highest band, band A (11.6 to 22 mc) seems to be working well with no noticeable issues. Band B (5.5 to 11.6 mc) also seems to be OK. It was too early in the day to really test band C (1.7 to 5.6 mc) although I was picking up a couple signals in the 60m band.
Not sure what to do from here - try probing further, or just let it go and call it good enough.
I really think that part (8), the band C RF coil, has been replaced with an incorrect replacement, and this may be the source of the trouble. The primary of this coil is also used on the AM band. The primary should have a resistance of 80 ohms according to the schematic. This coil doesn't quite match the drawing on the schematic, and its primary has a resistance of 120 ohms. (And maybe this is why the wires of this coil looked like the coil had been removed at some point - maybe it was removed from another Philco set!) I suspect that this may be an AM RF coil from some Philco set.
As always, I'm open to suggestions...a replacement coil is, most likely, unobtainium...
--
Ron Ramirez
Ferdinand IN
