[Milsurplus] [ARC5] 28 volt transformer question ?

[Mark K3MSB]

This is what I use in my main 28V ARC-5 RX supply;  cap input filter then a
regulator with pass transistor.

Mark K3MSB


On Mon, Sep 7, 2020 at 11:04 AM Richard <brunneraa1p at comcast.net> wrote:

> 39 volts is plenty of head room for a simple voltage regulating  circuit.
> I've done this many times.
>
> Richard, AA1P
> On 9/7/20 10:47 AM, Mark K3MSB 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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