06-07-2011, 08:00 PM
Hello and welcome.
Having never owned a 37-89, I looked at the schematic just now and I find the use of the choke quite interesting. Looks like this is how B+ is fed to the plate of the RF amp tube, as the signal goes through a 1 pF cap to an intermediate (RF) coil, and then on to the signal grid of the 6A8G. So...I would guess the 2.5 mH choke would be fine for your application.
As for the AVC line or lack thereof in your 37-89's IF circuit, I would connect it back as shown in the schematic. If the brown wire is connected to ground, the IF amp will not receive any AVC voltage, and that stage could go into oscillation as a result.
There were some changes in the 37-89 circuitry; you can find these changes in the "Changes in Models" PDF I have made available to Philco Phorum members.
http://www.philcoradio.com/phorum/showth...hp?tid=215
Having never owned a 37-89, I looked at the schematic just now and I find the use of the choke quite interesting. Looks like this is how B+ is fed to the plate of the RF amp tube, as the signal goes through a 1 pF cap to an intermediate (RF) coil, and then on to the signal grid of the 6A8G. So...I would guess the 2.5 mH choke would be fine for your application.
As for the AVC line or lack thereof in your 37-89's IF circuit, I would connect it back as shown in the schematic. If the brown wire is connected to ground, the IF amp will not receive any AVC voltage, and that stage could go into oscillation as a result.
There were some changes in the 37-89 circuitry; you can find these changes in the "Changes in Models" PDF I have made available to Philco Phorum members.
http://www.philcoradio.com/phorum/showth...hp?tid=215
--
Ron Ramirez
Ferdinand IN
