HISTORY:
I hear you asking "what on earth is this Russ?"
What you are looking at is a dual rail low voltage power supply COMPLETE but not housed.
Quality build, this was a prototype model used in audio preamplifiers, noise gates etc that were manufactured some years ago but all production has now ceased.
Output voltage is currently set at 16.5V DC +/- rails with respect to common or ground. Intended for use with Op amp based low level audio circuit designs.
Read on ....
UNBRANDED - Dual Rail Power Supply
Made in Australia using some UK components (NOT Asian!)
Output voltage is determined by both the AC voltage output but more importantly by a pair of 3 terminal regulators (317/337 series adjustable voltage) capable of 1.5A current but the transformer is a 3VA per secondary so around 150mA is much more "comfortable" - ample for most low level audio circuits
So let's step through the various modules you can see in the photograph.
The large rectangular shaped metallic "box" is the IEC AC power input socket (male) with incorporated fuse and EMI suppression filtering.
This goes off to the AVEL (UK) Epoxy encapsulated PCB mounted step down transformer, this has a dual AC 120V primary and dual AC 18V @ 3VA each winding. On the PCB is screen printed labelling to show which links to use for either 120V AC input or 240V AC - it is currently strapped for 240V operation.
The "underside" of the PCB (single sided board) has the 2x full wave rectifiers using 8 diodes in total.
At the front side of the PCB is an ON LED, this is Blue.
So this module with the transformer has 240V going in and approximately 20V DC +/- leaving the board, NOT FILTERED.
It was decided (due to lack of real estate inside the equipment box) to use hard wired filter capacitors (the blue ones) and they are 4700uF 25V irh capacitors (yes imagine that! irh capacitors have been "gone" for a long time!) Those two filter capacitors are soft glued together and actually used to be mounted the same way on the base of the equipment case - of course this arrangement can be varied to suit the new owner's purposes.
Now the 20V DC (dual rail) is filtered and goes off to the small module with the LM317 & LM337 3 terminal voltage regulators and associated control passive components.
You could change the resistors (again it's just a single sided board) to make custom changes to the output voltage(s) if you wished.
The regulators sit on a nice metal heatsink arrangement which is then intended to be secured to the equipment casing (no insulators required)
Lastly there is the Green/Yellow heavy wire which is the voltage Ground, connected directly to the equipment case and daisy chained to each module as well.
COSMETIC CONDITION:
An oldie but a goodie!
No stress to any components, electro's look fine too!
The transformer is A1 and actually a little ripper, these are from Essex UK and great performers!
DIMENSIONS:
To work out the size or real estate required to fit this into some equipment, here are some dimensions that will be useful
AC INPUT BLOCK (EMI Filter, Fuse etc)
28mm x 31mm x 46mm deep
AVEL TRANSFORMER WITH PCB
48mm x 90mm (including the protruding Blue LED) x 33mm height (standoffs are included because you need this clearance from the chassis due to the components on the UNDERSIDE of the PCB)
FILTER CAPACITOR BLOCK
35mm x 45mm x 20mm height
VOLTAGE REGULATOR
51mm x 38mm x 12mm height
TOTAL WEIGHT (ALL MODULES)
300g
TESTING:
AFTER removal from the prototype unit, I checked the power supply - exactly 16.52V on each side (RED plus & BLACK negative with WHITE common)
Ripple extremely low, my test equipment is these days pretty rudimentary (sold all my "nice" test gear) and whatever ripple was there was barely readable although this was under NO LOAD conditions anyway.
Why go out and buy all those parts when you have a complete power supply ready to roll for next to no money? I really don't like the idea of sending this to landfill, such an environmental problem AND all that Ee being thrown away! What on earth is Ee? Take a look HERE
