The PHILCO Phorum
Philco 38-3 alignment - Printable Version

+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: Philco 38-3 alignment (/showthread.php?tid=21305)


Philco 38-3 alignment - DuMont - 05-10-2020

Completely following the instructions for aligning the Philco 38-3 on the schematic and completely getting nowhere.  Performing the IF align first, then moving to the RF.  The mag tuning switch is closed.  I have a digital frequency counter in line with my signal generator.  I connect the signal gen lead to the cap of the  6A8G, and have tried it with and without the usual lead also attached. Negative for the sig gen is attached to the chassis.  Once I think I've lined up the IF circuit, I can hear the tone continue as I turn the dial to the first position for starting the RF alignment.
The closest I'm able to get is about 60 KC away from where a station should be.  IE, 1080 is coming in at 1020, 650 is coming in at 590, etc.
When the rotary dial is fully closed, it's in line with the tuning gang, so I know it's not off.

I'm getting plenty of clear stations, they are just not in the right place!!!!! Icon_crazy

RE: Philco 38-3 alignment - RodB - 05-10-2020

So, the oscillator seems to be working OK, just at the wrong frequency. You should be able to adjust trimmer 27 to move the oscillator frequency. Try tuning to a station then tweek the trimmer slightly to see if the station moves up or down the dial. With so many trimmers, you could be on the wrong one.

RE: Philco 38-3 alignment - DuMont - 05-10-2020

Thanks Rod, I'll give that a try.  I am watching on a multimeter and also listening as I go through the alignment process to get the highest peaks possible.
I just can't turn the volume all the way up - it kills my ears!!!   (and the cat has put out a contract on my life)

RE: Philco 38-3 alignment - DuMont - 05-10-2020

Rod, that closed the gap by half, but I'm out of room to adjust 27 any farther...