[Ron Ramirez]

May 20.

I had promised myself to not touch this 38-690 again until June.

But I had to know...was the fault in the RF unit as I suspected, or somewhere else within the radio?

So...I set the whole thing up (both chassis, woofer, and both tweeters) on the workbench and tried it out.

[Image: http://www.philcoradio.com/images/phorum...90_072.jpg]

With the 690 set to band 1 (AM), I fed a 470 kc IF signal into the grid cap of the mixer tube.

Guess what...the signal came through loud and clear.

While removing the signal generator lead from the grid cap of the mixer tube, I happened to notice that when I touched that grid cap with my finger...I started hearing AM noise!

So I connected a temporary antenna to the mixer grid cap and found that I could easily tune in my home AM transmitter (but nothing else on AM). I was also picking up some faint signals on one of the SW bands - Band 3 or 4, I think.

A-HA! I was right - there was a problem in the RF unit!

Hear the 690 for yourself, receiving my AM transmitter with a wire connected to the mixer tube grid:

[Video: https://youtu.be/d8fBMWCy7-U]

So...while I had the thing up and running, I went ahead and aligned the IF strip.

My next job is to remove that RF unit (again). Here some of you may disagree with my plans - that's okay, as Rev. Mason used to say, you have every right to be wrong if you want to be.

I am going to rebuild the RF unit I obtained from Mike Schwartzman and see if it performs any better.

Oh, and by the way, are the 38-116 Code 125 and 38-690 Code 125 RF units identical? As I mentioned in post #14, page 1, this thread:

The RF units of both radios are identical.

I will recheck the audio interstage transformer as well as the audio output transformer. Both showed good continuity when I rebuilt the amp chassis, but it will not hurt anything to recheck.