Philco 38-690 Oscillator Not Working? - 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 38-690 Oscillator Not Working? (/showthread.php?tid=19825)

---

Philco 38-690 Oscillator Not Working? - NV3G - 04-02-2019

I have strong audio signals and strong IF signals. I am receiving no stations at all.

The local oscillator does not seem to be working. Oscillator voltages are as follows:
Pin 3 - 191.8 VDC
Pin 4 - 93.0 VDC
Pin 5 - 1.58 VDC
Pin 6 - 195.5 VDC
Pin 8 - 2.53 VDC
Grid Cap - 0 VDC

The mixer voltages are as follows:
Pin 3 - 238.1 VDC
Pin 4 - 99.7 VDC
Pin 5 - 1.58 VDC
Pin 6 - 99.7 VDC
Pin 8 2.53 VDC
Grid Cap - 0 VDC

Shouldn't the pin 5 of the oscillator grid measure a large negative voltage? Does the OSC CONT tube
have control over the oscillator?

Thanks for any suggestions and help.
nv3g
Oscar

---

RE: Philco 38-690 Oscillator Not Working? - Radioroslyn - 04-02-2019

>Shouldn't the pin 5 of the oscillator grid measure a large negative voltage?

I wound think so also the control grid of the mixer too as they wired together.

If you are not seeing any -voltage there you may want to check the normal suspects. These being a dirty band switch, weak 6A8, or bent plate on the osc section on the tuning cap. Did you replace ALL of the foil paper caps in the sub chassis? A missed one could kill the osc. If you removed the sub chassis is it wired in properly?

>Does the OSC CONT tube have control over the oscillator?

Yes it does via the magnet tuning circuit. Don't think that it would stop the osc from working.

---