|[AMRadio] Pw Supply|
jack at schmidling.com
Wed Dec 6 10:04:53 EST 2006
Brett gazdzinski wrote:
> I would not buy anything from MFJ!
The transformers are Ameritron for whatever that is worth.
> Why the big hurry, wait to find a good transformer,
> they are around.
I have wanted one of these since 1955. I have waited long enough
besides, at my age, time is at a premium.
> What ratings are you looking for?
Good question. Actually, I was going to post a question so I could
answer that one.
I can't make any sense out of the 813 specs, either in the Handbook or
the data sheet I got on line.
As near as I can tell, the "typical" voltage for AM is about 1300 but I
see the Maul talking about 2000. I see plate current at about 150 but I
see elsewhere 250. I am sort of confused but think that 2000v ct at 1/2
amp would do the job.
> Is it supposed to fit on the deck over that big hole?
> Fair radio used to sell a nice oil filled Collins
> transformer, 2250 volt ct at 650ma, 110 or 220 primary.
> With a variac that would give 0 to 1500 volts.
I don't see anything like that on their site but I will check further.
> Its always much better to go with choke input, much better
> voltage regulation, much lower startup surge current.
> With a cap input, the voltage will increase quite a bit,
> but will sag big time under a load.
Good info. I read somewhere about needing some sort of step start and
mine has a time delay relay but it doesn't seem to have anything to do
with charging caps. It connects to something in the RF deck which I
haven't run down yet. It has a high/low switch which applies either 110
or 220 to the primary of the HV trans. Would this be adequate step start?
> What are you going to run off the supply?
> 8UF is not very good for a modulator, I always go
> around 40UF for energy storage.
Unfortunately, I want to run the modulator and rf deck from this supply.
That would be 813's/811's.
This package I bought was a linear so that could explain the too low cap?
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