PRC-2000
An AC Mains Supply for a battery operated rig.
The PRC-2000 is a modern, military tactical HF man-pack transceiver. Manufactured in the United Kingdom by Philips-MEL, the PRC-2000 covers 1.6 MHz to 30 MHz in 100 Hz steps. Modes of operation are USB/LSB, Data and CW and power output is 20 watts in all modes. The case of the PRC-2000 contains the transceiver itself, an automatic antenna tuner and an integral battery box wherein one can place 15VDC worth of batteries for portable operations.
I purchased my PRC-2000 from Combat Radio in the UK who, by the way, are some of the nicest and most honorable folks I've done business with.
When my PRC-2000 arrived I was surprised to find not one but two battery compartment covers included in the package. One was mounted to the radio and one was still wrapped in what appeared to be original packing materials.
On further inspection, the spare battery compartment cover appeared to be somewhat bent. When placed on the radio, one could clearly see daylight between the central portion of the cover and the radio. The amount of bowing was way more than the spring loaded cover latches could possibly correct. Since the battery covers are equipped with 'O-ring' gaskets for water proofing this clearly would not do.
While I was contemplating ways to straighten out the spare batter compartment cover, I hit upon the idea of using it as a basis for an AC mains power supply. That would leave me with a good battery compartment cover for use with batteries and a very neat and tidy installation for AC power usage without modifying the actual radio in any way whatsoever.
A quick perusal of the various electronic catalogs revealed a power supply that would easily fit inside the battery compartment. It is a Lambda ZWS75PF-15 which produces 15VDC at 5 amps. Additionally, I found a suitable AC power connector / fuse / On/Off switch assembly that looked like it might fit. It is a Qualtek 764-00/003. The switch/fuse/connector combination would allow simpler construction.
Here is the process I went through to accomplish this arrangement.
First, I measured the actual amount of non-flatness of the battery cover using a surface plate and height gage equipped with a precise indicator. The battery cover has 0.036 inches of bow to it. (For you tool junkies, that is a Starrett granite surface plate, an Etalon (Swiss) height gage and a Starrett Last Word tenths indicator.)
Next came laying out the battery cover for machining. The power supply only just fits so mounting hole placement will need to be accurate. Machining marks were simply scribed into the paint on the inside of the bent battery compartment cover.
Next was setting up the battery cover on the milling machine in preparation for the various machining operations.
There were three machining operations to perform. First, five mounting holes had to be drilled for the power supply. Next, the areas around these mounting holes had to be faced off in order to present a flat mounting surface for standoffs. (The holes ended up being very near shoulders and ribs in the cast battery cover.) And, finally, the opening for the AC connector/switch assembly had to be machined out.
It was then a simple matter to mount the components and wire up the molex connectors to hook everything together. Here's what the final assembly looks like:
At the bottom is the battery compartment cover with the AC connector/switch assembly barely visible. The power supply is mounted on standoffs in order to clear the AC connector and the battery connection pins inside the battery compartment. Here's a different view of the final assembly where the AC connector is more visible:
And, here it is all buttoned up and ready for service:
