|[AMRadio] Re: Pw Supply|
ne1s at neandertech.com
Thu Dec 7 13:20:01 EST 2006
See comments/answers below.
Jack Schmidling writes:
> MFJ has a 900v one for about $100. Is there any reason why I can not use
> two of these and tie one side of the secondaries together and call that
> the center tap and have an 1800v ct transformer/s?
Jim Candela has already given the correct answer ("no"), and why.
> I am using 866's so I must have a center tap.
Not necessarily! Use 4 866's in a full-wave bridge. But this will require a
minimum of 3 filament transformers for the 866's.
> Second question is:
> Mine has the HV going to the choke and then to two 4 mf 3kv caps in
> parallel. Is it not more conventional to put a cap on each side of the
> choke or two chokes for a choke input filter?
Choke-input and capacitor-input filters have very different voltage outputs,
not to mention dynamic voltage-regulation. Also, mercury-vapor rectifiers
get VERY UNHAPPY looking into capacitor-input filters. If you use MV
rectifiers, you MUST use a choke-input filter. With a choke input filter,
you need to be cognizant of the minimum current being sourced from the
supply and the required critical (minimumum) inductance of the choke. Do you
have a period (1930's - 1950's) handbook you can review?
> What would I gain or lose by moving one of the caps to the HV side?
If you use cap-input with MV rectifiers, you'll at least lose the
rectifiers! Otherwise, you'll gain unloaded output voltage, at the expense
of poorer dynamic voltage regulation, & put more stress on *(from higher
peak currents in) the (SS diode or vacuum) rectifiers and plate transformer.
I thought this has mostly already been covered in this thread?
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