[R-390] Re: Image Problem

[Jon Schlegel]

Tony,

Could this be environmental?  Corroded downspouts/eves troughs and 
who knows what else can sometimes turn into unwanted rectifying 
devices complete with integral antennas.

JS

At 04:58 PM 10/21/2007 -0400, you wrote:

>Tony,
>
>When you measured the  voltages below what was the gen input voltage?
>
>Voltages are
>
>With  no AGC applied:
>Plate 201v
>screen 178v
>cathode 2.1v
>grid  -.5v
>
>With AGC applied:
>Plate 215v
>screen 201v
>cathode  .22v
>grid -4.2v
>
>
>The agc, with the Langford mod, should be  about:
>
>10 Uv rf input = -4.36 Vdc
>100Uv rf input = 6.66
>1000 Uv rf  input = 8.53
>
>I don't know if this will help, but you are talking some  very big rf input
>voltages (20mv).
>
>I also had a problem with the Ist rf  amp not responding to the AGC voltage
>once.   Tube tested good and the  agc voltage was there.  Was fixed with
>another rf amp tube.  That took  a lot of work.
>
>By the way, if you use In914 or In4148 diodes in that  Langford mod I've
>found that one of the diodes will fail.  I use  1n5060.  I think 
>it's breakdown
>when the AGC switch is turned from slow to  medium. This has happened in at
>least 5 IF decks.
>
>Rich WD2Q
>
>
>
>
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