[NJARC] "Selective" shadow meter...

[Al Klase]

Hi Steve,


READ ALONG IN TH SCHEMATIC.  The shadow meter (76) is in series with the 
plate voltage feed to both the RF amp and the first IF.  These tubes are 
both controlled by the AVC circuit, and draw maximum current when the 
signal level is low, and less current as the signal strength increases 
and the AVC voltage goes more negative.

May I assume, that on strong stations, the "action" of the meter is 
similar to what you see in this video:
http://www.youtube.com/watch?v=cnTANNu6lo0
Jump to about 3:00.  There's a lot on nonsense at the beginning.

If the meter movement works OK, Then we have to assume your radio is 
hard of hearing.  The problem could be in the RF amp, mixer, either of 
the IF's or the detector/avc.

1) Test the tubes.

2) Next step is to check the TUBE SOCKET VOLTAGES per the table in 
Rider's.  the voltages will like rad a bit high on a DMM or VTVM rather 
than a VOM, but you're looking for things that are really out of whack.  
(Like almost zero screen grid voltage, etc.)

3) Only after 1) and 2), align the radio.

Good luck,
Al




On 7/12/2013 10:31 AM, sgt88 at atlanticbb.net wrote:
> Just remember
> Reply = Poster
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>
> _________________________________________________________
> ...in my Philco 116X...it works fine on two local AM 
> stations...only...got weak stations across the AM band...but would not 
> expect much movement on them.
>
> I get no 'satisfaction'...shadow movement...anyplace else = shortwave 
> stations.
>
> Everything I've read has to do with trouble-shooting a non-working 
> unit...not one that is 'selective' like this one.
>
> Suggestions welcome,
> Steve T.
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-- 
Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/