[Amps] QST

[Tom W8JI]

>     I am becoming more and more disgusted with the lack of 
> technical
> knowledge QST authors.   A fine example is the article 
> about reviving old
> linear amplifiers in the most recent QST.   There is a 
> schematic and
> description of a half-wave voltage doubler which is 
> claimed to have been
> used on many older amplifiers. But, everyone that I have 
> seen uses
> full-wave voltage doublers. The only half-wave voltage 
> doublers I have seen
> are usually in TV sets and other tube equipment that 
> operated off the power
> line with out a transformer.


The same author in a solid stat amp article made a series of 
mistakes, including using an ALS600 power transformer 
without the filter choke. The ALS600 is designed to use a 
filter choke. Use without the choke would result in about 
80-100 volts on the 50 volt FET's. That's a BIG error.

Also Motorola's board has some design issues, so it isn't 
just QST authors who could use improvement.

The only thing in the article I saw sticking out was he 
recommended using small 470k resistors across the diodes. 
Bad idea.

The rest of the errors are what I would call small

73 Tom