[markmokris]

I have restored about a half dozen Philco 19 and 89 cathedrals and have spent many hours winding and rewinding the oscillator tickler coil trying to get satisfactory results.  Mostly I have been successful.  I have gotten every radio to work pretty well and the 36 tube autodyne to oscillate and perform across the AM band.

I have a Philco 19 that I restored a number of months back, rewound its coil, and it had been performing well. But recently, it began to consistently drop out below 1000 Khz, the typical spot as I have learned.  I decided to make Ron's mod with the 77 tube, which is pretty easy, except for installing a replacement 6 pin tube socket for the 77 tube to replace the 5-pin 36 tube (not easy  ).

That actually worked great.  I posted my experience about that a while back.

http://philcoradio.com/phorum/showthread.php?tid=16145

Every once in a while, I would turn the radio on and after warmup, the oscillator wasn't kicking in at all.  Consistently, flipping the radio off and on fixed it immediately.

I have been wanting to do Ron's 6A7 tube "Super Oscillator" modification, so I decided not to leave well enough alone and give it a try. It's a very well done tech tip by Ron, and if you have researched the Philco 19/89 threads, you undoubtedly have seen it.

http://philcoradio.com/phorum/showthread.php?tid=14919

Steve Davis just recently posted his experience with this mod.

http://philcoradio.com/phorum/showthread.php?tid=16467

I swapped out the 6-pin socket and replaced it with a 7-pin socked to hold the 6A7.  Rather than perform the arduous task of rewinding oscillator coil completely (I even bought a crank-handle coil winder for the task), I thought I would try using the stock PSC-70-OSC oscillator coil available at AES for 9 bucks.  

https://www.tubesandmore.com/products/coil-oscillator

I had used this to replace the oscillator coil on a Philco 38-12, it it worked great!  That is a 6A7 oscillator converter circuit that looks very similar, so I figured my chances of success were high.

The net result is that it works well!  So I thought I would document what I did in case someone else might want to make Ron's Super 19/89 mod without having to rewind the coil.

Here is a circuit diagram that I ended up using with the coil pinouts noted on Ron's circuit.  

   

I attached colored wires to the pins and mounted the coil on a piece of aluminum up inside the oscillator coil can.  The color choices were mine, and you can refer to the pin numbers to identify the actual connections.

   

   

   

After wiring it up carefully, I got nothing.  It took an hour or so of troubleshooting to determine that the band switch decided to become intermittent.  After some fiddling, the radio came to life.  The dial was a bit off, but I found the strongest station on the band, and adjusted the slug inside the PSC-70-OSC coil to move the received station down to its correct place.  Tracking is pretty good across the band.

A couple things to note.  I found that a good place to wire the 110 mmf capacitor is right across pins 3-5 of the coil.  It saves trying to find a connection point somewhere else under the chassis.  Also, I might add two steps to Ron's list, if you are using the steps as a checklist.

a. Be sure to disconnect the secondary of the (6) RF coil from ground and make the connection to the AVC buss.
b. Connect pin 2 (plate) of the 6A7 tube to the primary of the (18) IF coil.

Certainly if you follow Ron's schematic, you will not miss these steps.

I don't know how well the SW (police band) works after this mod. On these radios, I guess I have a bad habit of not really caring .

I think I am now going to remove this coil, and wind and wire up the coil that Ron documents in his "Super 19/89" techtip. After all I did buy the coil winder and I cannot leave well enough alone.

Mark K8KZ