Re: [Hallicrafters] Question on Solid State replacements…

[W7QHO at aol.com]

In a message dated 9/9/07 5:15:45 AM, jew123 at juno.com writes:


> I have question about Solid State replacements for the 5Y3/5U4.  On the 
> schematic from Bama for my SX-99 the B+ is taken off pin 2.  When I repaired 
> radios and TVs as I remember the power was taken off pin 8.  If the Solid State 
> replacement uses pin 8 as the B+ take off pin then I would have 5 V AC in 
> series with the B+ right?
> 
> On the schematic from Bama for a SX101 Mark 2, the B+ is taken off pin 8 
> which I always thought was the standard.  In a tube 5Y3/5U4 it does not matter 
> which pin but if the Solid State replacement use pin 2 it would be okay for my 
> SX-99 but for the SX101 Mark 2 which takes B+ off pin 8 then it would have 5 
> V AC in series with the B+?
> 


Jim,

Right and right again, but don't worry about it.   The 5 volt, 60 Hz 
component gets filtered out along with the 120 Hz component in the rectified HV. If 
you disconnected the receiver's power supply filter and looked at the pulsating 
HV coming out of the rectifier with a scope the 5 volt (RMS), 60 Hz series 
component would appear as a   2 X (5 X 1.414)   = 14.4 volt variation between 
successive voltage peaks.

Dennis D. W7QHO
Glendale, CA



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