My article on the Navy RBS-2 (in The Spectrum Monitor, August 2022), includes the following note on the power supply. I used 47 uF caps at 400 volts because I had plenty of those.

"On final testing of the supply with the receiver as the load for both filaments and B+, the filament side with its 2 ohms added resistance provided almost exactly 12 VAC. The 1500 ohm total resistance on the B+ side, provided a DC voltage at 216, also nearly on the nose. The alternate B+ connection ahead of the third 500 ohm resistor was 244 VDC, thus a calculated B+ draw of about 56 mA. The line power drawn by the supply was 57 watts and 0.52 A according to my Kill-a-watt meter.

Given the size of the UPS transformers, I saw no reason why the supply would not be able to supply nearly twice the power requirements for this receiver. If a future project needed 6 volts for filaments, a similar arrangement using the center tap on the first transformer would meet the need. The supply could be also stiffened a bit by using larger electrolytics if needed but there was no detectable hum on the RBS-2 with the size of the electrolytics I had chosen."

Rich KB8TAD

On Sat, Apr 29, 2023 at 5:20 PM <hwhall@compuserve.com> wrote:

The older ARRL Handbooks had a graphical solution for selecting the resistors & capacitors for voltage doublers.

Wayne
WB4OGM

-----Original Message-----
From: Rich Post <kb8tad@gmail.com>
To: n2lxm@juno.com
Cc: arc5@mailman.qth.net; milsurplus@mailman.qth.net
Sent: Sat, Apr 29, 2023 2:37 pm
Subject: Re: [ARC5] R-508/ARC Conversion

I needed a power supply for a Navy RBS and decided to build one using modern surplus junk, a pair of back to back transformers from dead UPS (putting the second transformer from an APS 350 into the empty battery compartment of the first UPS, an APS 280.) I had earlier made a similar conversion for powering an ARC 5 transmitter at QRP levels but wanted more voltage. For the higher voltage, I used a doubler on the output. It worked great for the RBS. Change resistors as needed to get the current at the voltage wanted. Here's pics of the circuit board and the simple schematic.

Rich KB8TAD

On Sat, Apr 29, 2023 at 12:11 PM <n2lxm@juno.com> wrote:

Greetings All,

Has anyone converted an R-508/ARC using the article in the June
1965 issue of 73 Magazine ?. I would like to get this old girl running so
I can listen in on out local airport Automated weather transmissions.

Jeff N2LXM
Amateur Radio Operator
American
Patriot
Proud Father of Two US Marines

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