Fw: [Hallicrafters] Solid State rectifiers vs Vacuum Tube rectifiers

[Jim Wilhite]

As I recall the tolerance for mains in the 50s was 115 +/- 10%.  So 115
V. + 10% would be 126.5 and - 10% would be 104.

Higher voltages were found in rural areas or close to a capacitor bank
to boost the voltage for the longer run.  At the end of the line it
could easily be 105.

The manuals for equipment built then said 115-117 V +/_ 10%.

Jim/W5JO




If the filters are original a surge limiter would be beneficial but of
no use if replaced with modern caps. The transformer surge current is
limited to the flux density of the core. Since the receiver
manufacturers counted every penny there wont be any excessive draw at
turn on.

Even a slight bit of higher B+ wont harm anything since the USA AC
mains were anything but standardized in the old days. Anything from
105-117 or more was the norm. The danger is to the tube emission;
oxide coated cathodes can be seriously harmed when the filament
voltage exceeds more than 5% or so over design spec.

Carl
KM1H

>>
>>
>>
>>> Solid State Rectifiers ,BAD idea! The B+ Voltage  goes WAY UP more 
>>> than the
>>> original circuit specs ,plus the power transformer receives a SHOCK
>>> EXCITATION every time the rcvr is turned up thanks to the incoming 
>>> surge current  ,no
>>> charge on filter caps so HUGE starting current. Of course one could 
>>> add a
>>> surge protection resistor. Slow warm up of the original rectifier 
>>> tube allows a
>>> gradual build up of B+ voltage as opposed to the instant turn on of 
>>> a solid
>>> state rectifier.
>>> Nick
>>>
>>>
>