[Johnson] Modifications

[Sherrill E. Watkins]

While we are discussing the pro and con of modifying classic equipment, I
would like to state that some of the worst mods to do to classic equipment is
to "solid state" the rectifier in the power supply. Unfortunately, this is
easy to perform and the owner thinks he has "improved" the equipment because
he has eliminated the rectifier tube. As explained previously in articles
both in ER Magazine and the Old Timers Bulletin, the instantaneous
application of high voltage to the plate of a cold tube is a sure way to
destroy the tube. Also the solid state rectifiers increase the voltage level
over the tube rectifier thereby causing the equipment to run hotter and
additional stress is placed on all of the components. Classic equipment will
be damaged by the simple addition of solid state rectifiers and this must
NEVER be performed. Also, classic equipment should be operated at a low AC
line voltage and never at the high (120-125 levels) that is common today. My
AC line voltage is 125 VAC and I understand this is quite common. For older
equipment, 110 to 115 maximum would be better.-73- Sherrill W. k4own.