[Milsurplus] [ARC5] 28 volt transformer question ?

[Mark K3MSB]

Oh sure.   But, when you need something "now",  Old Rube beats the Greenies
hands down in my book.

Agreed about the variac.   I usually find them at hamfests and will pick up
3 to 5A units for $5 to $10.   Nice to have a supply on hand.  The best
place is the corporate dumpster.   We moved facilities a few  years ago and
I salvaged about 4 or 5 units.   They were fine;  not sure why they were in
the dumpster,  but we were told dumpster diving is permitted and
encouraged......

73 Mark K3MSB

On Mon, Sep 7, 2020 at 10:57 AM J Mcvey <ac2eu at yahoo.com> wrote:

> Well, it might be a great setup in a cold shack. It would get a 25 watt
> resistor nice and toasty.
> I did things like that when I was a kid who only had "available materials"
> to work with.
> Yes, it works, but it's wasting power in the "brave new green world" and
> rather Rube Golberg-ish.
> The variac would be my choice.
> Better yet, a transformer better suited for the task.
>
> On Monday, September 7, 2020, 10:47:30 AM EDT, Mark K3MSB <
> mark.k3msb at gmail.com> wrote:
>
>
> I disagree.    If for a receiver,  the current draw is constant and a
> suitable dropping resistor can be used.    I've done this frequently with
> ARC-5 receivers.
>
> Or, just put a variac in front of it and drop the input voltage.
>
> Mark K3MSB
>
> On Mon, Sep 7, 2020 at 10:42 AM J Mcvey via ARC5 <arc5 at mailman.qth.net>
> wrote:
>
> Using that xfmr with full wave rectification and filter cap would yield
> about 39 volts out.
> So, it's a good candidate for the scrap yard.
>
>
>
> On Sunday, September 6, 2020, 11:10:08 PM EDT, Hubert Miller <
> kargo_cult at msn.com> wrote:
>
>
> I had this AM-FM broadcast receiver, with step tuning, and the logic
> developed a problem.
>
> As you know, these are impractical to repair, with this kind of problem,
> uneconomical.
>
> Well, in my city, there is very limited collection of ewaste, and an
> irrational I think, regulation
>
> of categories. So instead of tossing the whole thing in the garbage, I
> disassembled it, tossed
>
> the cabinet and chassis in the recycle, and the circuit boards in the
> regular garbage.
> I found that the power transformer is 28-0-28 volts and looks good for a
> steady 5+ amp. What
>
> I'm wondering, should I keep this for a dynamotor spinnner, for dynos like
> the command sets
>
> or RU-GF class? With a filter cap, the output should stay "near" 28 volts
> under load. You just
>
> don't want to have such PS charged up to peak and then connect it to the
> load, which might
>
> be hard on tubes. Or what if I just used it without filter cap, to spin a
> dynamotor? Or instead,
>
> go ahead with a multiple thousands mFd filter cap and maybe a small series
> resistance to
>
> adjust voltage under load?
> Many years ago I used such a brute force supply I bought from Fair Radio
> to power an ARR-15
>
> receiver. At that time, I didn't even think to worry about the exact
> output voltage.
>
> So what about this transformer? 24 volts would be preferable but the price
> on this one was
>
> right.
>
> -Hue Miller
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