Model 620 distortion - 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: Model 620 distortion (/showthread.php?tid=296)

---

Model 620 distortion - Guest - 03-06-2006

Hello,
Here I go with yet another question, but they say if you dont ask you wont learn. My 620 once warmed up and I tune in a radio station,lets say 1370 AM, if I have the volume set as I near the station its clear audio but low but once dead on 1370 it gets louder which it should because im now on freq but it distorts, is this the cause of a bad speaker or what ??

If it is a bad speaker then Im in need of one any help there ??

Thanks for all your support in the past with my silly yet need to know questions.

---

Distortion and volume problems - AI2V - 03-11-2006

With little doubt you have an open grid resistor in the triode section of the AM detector tube (75) or possibly the audio output tube (42).

With the power off, check the resistance of the 1 meg resistor #35.

If that is OK check the 500K (0.5Meg) that connects to the grid of the audio output tube (42); or, measure the grid voltage- usually -20-25VDC.

The higher the value of resistor means the higher chance of increased resistor value. 20% error fine; above that means change it.

Let me know what you find.

---

- Terry Burns - 03-12-2006

Hi John,

I think Pete has it right on checking your resistors on the audio tubes. One other thing to check is if you tuned into a strong station and it distorted I would look at my avc resistor and cap. Possibly a 2 meg and a .05 cap?

Hope this helps
Terry

---