[Amps] power supply transformer

[Michael Tope]

----- Original Message ----- 
From: "Tom W8JI" <w8ji at w8ji.com>

> 
> You should use a transformer for a few reasons (as was 
> already covered) like line surges and safety. It is against 
> code to EVER ground a neutral to anything connected to 
> something external, so the neutral has to float. You could 
> float the entire negative rail from chassis, but then the 
> issue becomes spikes from the power line into the PA and 
> harmonics from the rectifiers into the power mains. You 
> certainly could design a system that would use the power 
> mains safely and not break codes, but it would require some 
> care.
> 
> The real problem is knowing the ESR of the transformer. 
> Certainly it isn't as low as it could be because of the fact 
> it is a control transformer, but a choke input would help a 
> lot. You could get a power factor close to unity rather than 
> the very poor power factor of a capacitor supply, so you 
> might be OK if the choke is a good one.
> 
> 73 Tom 
> 

Sounds like a good application for a switch-mode supply. 

Mike W4EF..............................