[R-390] Should this work?

[Roy Morgan]

At 10:14 AM 5/5/2005, you wrote:
>I then decided to take the IF output from the working radio's RF deck (with
>the radio tuned to a good strong station) and plug it into the input of the
>IF deck on the radio under test.

Barry,

Good idea.  Does the non-working radio show any RF signal level on the 
meter?  Probably not.  It sounds like your RF deck is not putting out any 
signal(s),

Have you put some 455 kc signal into the INput of the IF deck?  Try that next.

Then run some signals into the test points on the RF deck. Start just 
before the last mixer and work forwards toward the antenna. (use a 
capacitor to couple the signal in, there are likely dc grid voltages at 
some points.)

I wish I had a little table of frequencies to share but I have not made one 
up yet.  We need a troubleshooting aid like this: frequencies and normal 
voltages all along the RF and IF chain, by receive band and frequency.  The 
manual IF gain setting procedure gives you a number for the IF input voltage.

You may have a broken wire in the cable feeding B+ to the RF deck or some 
other place.. test for B+ at a plate pin of both if deck and rf deck.

>Is this a valid thing to try?

Yes, you did good. First see if the input of the IF deck gives you 
signals.. 455 kc in (at maybe 200 mv ?) Then, move towards the input of the 
radio with test signals.

I have at least two radios with dead RF decks.  A likely culpret is a 
shorted screen bypass cap, or open screen resistor.

Roy

- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Cell 301-928-7794
Work: Voice: 301-975-3254,  Fax: 301-948-6213
roy.morgan at nist.gov --