UK designed, manufactured
Ex Broadcast Industry equipment
Sustainability is a big thing to me, re-use worthwhile equipment or sub-assemblies makes so much sense and often is a far more cost effective solution than "starting from scratch"
Everything we have manufactured over the years has a measureable EE value (embedded or embodied energy) which gives a measure of how much energy was used to gain the raw materials and form those materials into finished products - the energy used is incredible (search embedded energy online, lots of active discussions about this subject) and then there is the sustainability of the raw materials we began with.
So what do we do once the product has been superseded? Bury it in the ground!
Humans are turning into the vandals of the earth! Poisoning our own backyards.
That's my philosophical view, now let's talk techie ...
Why bother building a dual rail supply from scratch when I have power modules, completely built, tested and ready to roll once again?
POWER SUPPLY (Variable Voltage Dual Rail & Fixed Rail)
240V AC input
Multiple outputs and options
Positive & Negative rail outputs, regulated variable
Range 12 ~ 16V DC @ 500mA each rail
Each rail can be made "common ground" or operated as two completely independent power supplies e.g one rail set for negative 12V DC and the other set for positive 15V DC
The "normal" use of this supply would be for Op amps which often require dual rail supplies in audio work at least
Easy access is also provided to unregulated DC (filtered of course)
I am supplying all components you can see in the photograph, i.e the torodial transformer, the mainboard with the two TO220 regulators hanging off it (and associated heatsinks)
COMPONENTS:
LM317T & LM337T variable voltage regulators (TO-220 case)
1A block rectifiers - full wave
2x 2200uF 63V 85C electrolytics (Type 4232 M)
2x PCB mounted 10K linear trimpots
1x Toroidal transformer LP (Made in UK) 120/120V primary & 2x 30V AC @ 0.5A (each?) with colour coding information
DIMENSIONS:
Toroidal transformer: 70mm diameter x 40mm height
Comes with all the necessary hardware
Main board (double sided): 106mm x 89mm x 36mm height
Hanging off one end of the PCB is the two regulators, intended to be mounting onto the chassis (full mounting hardware/insulators are supplied) and these extend the length from 106mm out to 126mm
All connections to and from the PCB are via PCB standoffs - no need to solder directly to the PCB
In the past I have used these modules to create a nice low voltage, low power benchtop power supply for general purpose use - most often to develop and test audio circuits (it can be very handy to change each "side" of the dual rail and observe what happens to the amplifier characteristics!
IDEA!
One thing I did though was remove those two trimpots and run 3 leads for each pot to my custom power supply front panel and used nice Bourne 10 turn panel mounting pots so that far more precise control of the voltage was achieveable very easily.
Those existing trimpots on the PCB are TOUCHY, just very slightly movements on the pot track and the voltage swings all over the place!
COSMETIC CONDITION:
Complete, wiring intact and ready to go. Just organise your fuse/switch/EMI suppression at the AC input end, mount the PCB and regulators (with heatsinks) and some sort of output terminal arrangement and you are in business!
You may notice in one photograph that two wires (Orange & Black) are connected together and have heatshrink insulation over the joint. This is the primary leads of the AC transformer, the 120V windings (2) are connected in series for use on our 240V AC supply.
What you can expect at those PCB standoff tags
All tags have their purpose marked/etched onto the PCB
"Front" end of the PCB (near the electro's) is two tags, these are the supply for your front panel LED ON indicator
"Rear" end of the PCB is where all the action is:
In the middle of these tags are the connections for the raw low voltage AC from the toroidal step down transformer. So you have access to 2x 30V AC or if you rewired them in series, 60V AC (although this will drastically affect your power supply mainboard!)
Each side (to the right and the left) is a set of tags marked as REG, OV, - (or +)
REG is the regulated output, variable voltage under control of the user
OV is common or ground (two tags which are connected to a common solder pad)
- or + is a fixed DC voltage output - this is much higher than the regulated output as it is just the AC rectified, filtered and unregulated.
An example: If I measure between REG (-) and OV, I see -14.97V (set by the trimpot) but at the same time, if I measure between OV and the - fixed voltage tag, I measure 42V DC.
Also, on the example above I left the common strap in place so if I measure the between the fixed - & + tags, I read 86V DC (starting to get into "bite" territory now so be very careful!
NOTE: in normal operation there is a wire strap (black) between the two common's (OV) - this means the positive rail and negative are not connected "together" but by reinstalling this strap, you will have a + Common - DC output (normal operation in most cases) - you could even insert a panel switch here so that there was front panel control available.
I will be supplying these modules with this wire strap REMOVED - extremely easy to place a new strap in place.
