[NJARC] "Selective" shadow meter...

[Al Klase]

2) should read "...the voltages will likely read a bit high..." - Al

On 7/12/2013 1:13 PM, Al Klase wrote:
> Just remember
> Reply = Poster
> Reply All = Everyone
>
> _________________________________________________________
> 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
>> Reply All = Everyone
>>
>> _________________________________________________________
>> ...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/