[markmokris]

I have restored two Philco 19 cathedrals and one 89. There are pretty much all the same radio except the Model 19 has the shadow meter.

On each one I had to at least rewind the oscillator tickler coils. The 36 tube in this design has been know to be very temperamental, and after considerable struggle I got the all radios to work across entire the AM band.

Last week, I was playing one of the Model 19s, and son-of-a-gun, the oscillator was starting to cut out below 1000 Khz. I tried a couple different 36s, even new ones, and it wasn't making a difference. It was working at one time! I finally decided to make the change from the 36 to the 77 tube as described in Ron's tech tip #42 on the Philco Repair Bench.

http://www.philcorepairbench.com/tips/svctip42.htm

I thought I'd pass it along that the mod works great! The radio seems to perform stronger than before and doesn't cut out at all as I tune across. The hardest part was installing a different tube socket. The 5-pin Philco socket for the 36 has mounting holes positioned that I don't think you will ever find on any replacement 6-pin socket.

Drilling holes in that Fort Knox-like Philco chassis in exactly the right spots for the new socket wasn't easy. But I am glad I made the change, and wouldn't hesitate to do it on a future restoration.

Mark K8KZ

[morzh]

Mark

Great it worked for you, but in the first place if the oscillator cuts out even with new tubes, that might mean you have other problems as well.

[Ron Ramirez]

To elaborate on what Mike said...

If you really want a reliable 89 or 19, switch the 36 tube for a 6A7 as outlined here.

However, that is taking things to unnecessary extremes. Usually, an 89 or 19 can be made to work with the stock 36 tube. You have to do the following:

* remove the oscillator coil and bake it at 200 degrees for 30 minutes; preferably before rewinding the tickler winding which is always open;

* reduce the value of the 15K resistor between the oscillator tickler winding and ground to 10K or even 7.5K;

* replace the mica cap in parallel with the same 15K resistor with a new 680 pF mica or C0G/NP0 ceramic cap.