[ARC5] AC Power Supplies

[Dave Merrill]

On Mon, Dec 26, 2016 at 8:23 PM Brian <brianclarke01 at optusnet.com.au> wrote:

> Hello Dave,
> Very nicely made.
> My first concern is for the stress on the HT secondary winding at
> start-up, with direct feed to 94 uF of filtering. For trannie longevity, I
> would put small resistors between both filter caps and one between the
> rectifier and the first filter cap. 100 Ohm each will only drop the output
> HT Voltage 8 V. For a commercial example, Tektronix did this with all their
> solid-state, linear power supplies on their 500-series of CROs.
>

That's a good suggestion and I will add it to Build 2.0


> My second concern is those 20+ year old capacitors; electrolytic
> capacitors like running close to their rated Voltage. So, if they’re
> falling over – low C, high ESR – I’ld replace them with ones rated at 180
> to 220 Vdc wkg.
>

The code date on the capacitor can is 6704 so it is almost 50 years old!
Still working - I measured the ripple at .48 mV with no load and 2.2 mV at
50 mA load.  Since I'm a ham I used what was within easy reach, but I'll
remember to replace it with a more suitable working voltage unit at some
point.


> Dave Stinson, AB5S and I – and many others - will confirm that Command
> receivers work very well with 160 Vdc HT.
> Your 22k bleeder is a very good choice – hardly affects the output current
> available, and gives a 1/e Voltage drop every 2 s. Safe.
>

Good to know I got something right :-)

73, Dave N9ZC


> 73 de Brian, VK2GCE.
>
> *On* Tuesday, December 27, 2016 12:53 PM, you showed:
>
> Here are some photos of a power supply I built on a DM-10A base 20+ years
> ago.  I don't recall where the transformer came from but it had both 6.3
> and 24 volt filament windings so I allowed for both.  Cap is a dual section
> 47 uF @ 400 VDC connected in parallel.  Full wave bridge with a 22K bleeder
> resistor.  Produces 165 VDC @ 40 mA.
>
> There is a PC-8417 transformer with similar filament specs and 220-0-220V
> on eBay now - item 371821125244 (toober is the seller).
>
>
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