When restoring vintage valve (tube) radio equipment it is often desirable to have a bench power supply that can power individual stages without using the original power supply built into the equipment. It is also useful for the odd experiment we may wish to carry out by bread-boarding a few bits. Yes, these modern solid state folk have not got bread-boarding to them selves.
When I was very much younger and valve technology was current, I built several of these power supplies. Not one of these has survived in my collection so a few years ago I decided I needed to make one again. After a bit of "head scratching" I remembered the basic circuit of such devices and here is the result. This one is a bit different to ones I made in the past, it has a solid state bias supply of 1.2 to 30 Volt and switchable solid state regulators for the lower filament/heater voltages used. Although I could have used solid state devices for the high voltage supply, I have stuck with tradition and used a good old 6AQ5 as the pass device and three neons as the voltage reference.
The resistors I use are Caddock MP9100 50 and 100 Ohm date: 19th February 2015
The item in the first image is a capacitance leakage tester, a project featured in Silicon Chip magazine during 2010 and built from an Altronics kit.
The three items in the second image are, a ESR Capacitor Tester built from a kit from Dick Smith Electronics, a Silicon Chip project 50MHz Frequency Counter also built from a kit from Dick Smith Electronics and lastly a low range L and C Meter built from a project in Silicon Chip magazine. I could not find a kit for this and "rolled my own" using circuit boards from RCS Radio.
Sadly the Dick Smith kits are no longer available as this organisation has become a Super Market, now only interested in pushing out consumer electonics items, all the hobby items they once stocked were thrown out at bargain prices some time ago. Some of the kits featured in Silicon Chip magazine over the years are still available from Jaycar and Altronics and the circuit boards for a "role your own" were available RCS Radio but I believe this company has ceased to operate. Some project boards can be obtained from Silicon Chip magazine publishers.
I have bought this kit to use with my BoatAnchor equipment because it costs about the same as two crystals and they only give you one or two operating frequencies. This little kit gives you an infinite range of operating frequencies. As it only has one output my intention is to build a wide range VFO to use for the receiver sections of some transceivers that use one crystal for transmit and one for receiver per operating frequency This may even make a good radio club project. I have decided I put it into too small a case as it would be better to have a BIG knob on the frequency control, I may even build it into a bigger box with the VFO I intend to build. There are number of VFO kits available, I will look into them as I do not have the time to cobble up my own.
It will normally be powered from the Shack 12 Volt supply but I have included a 9 Volt battery pack so I can use it anywhere. I will also add a buffer / amplifer circuit inside the case when I work out what output level I will need in most applications. I will also have to modify any equipment I intend to use it by adding BNC connectors for the inputs and in the case of valve equipment even more amplification I suspect. If you look on my BoatAnchor Maine Transceiver page you will see two or three candidates for these conversions and some more on the BoatAnchor Outback Transceiver page
I have built several of these boards for members of the radio clubs I belong to who had difficulty with the surface mount components. The last two images show how I go about installing SMT parts. They can be built into a boat anchor receiver or VFO's and used as a frequency read out. The display can be offset for the IF frequency of the receiver. They are available from Hendrix QRP Kits
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Written by and Copyright, Phil. Storr © Last updated 1st February 2016