power supply ev0lution

I just picked up a bunch of stuff at the local hamfest and strangely enough it filled in a few holes in my power supply collection, so I thought I would do a post on the evolution of power supply modules. These are all linear regulated supplies, switching regulators aren't included because they really can't be used for audio or analog elelectronics. I pretty have one example for every decade, because blogger posts the pics in reverse order I'll start with newest to oldest.....

IBM blade server voltage regulator module, ca. 1998

I found this at a flea market, this is a double sided plugin card with all surface mount components and an extruded aluminum heatsink on each side. The whole thing plugs in on a gold plated edge finger connector with the contacts connected by multiple vias inside the connector pad, a neat way to reduce inductance. The decoupling capacitors are aluminum electrolytic and the active components are small chip scale packages under the heatsink, 4 or 5 if I remember right. This is meant for digital electronics (an IBM blade server) but it is still a linear regulator and has some really nice packaging. I grabbed it hoping to use the heatsinks but I think I might leave it intact, it is a really cool looking piece :)

Unknown triple output regulated power supply module, 1985

The first change is the thru hole components, everything since the late 80s has been surface mount so that is a good indicator of age. The pass components for each regulator are each on an extruded heatsink on the back of the module, a TO-3 2N3055 PNP and a smaller driver transistor. The regulation electronics are on a seperate PCB on the backside of the module. The heart of the regulator is a metal can regulator IC with some external components for setting the output voltage and a bit of filtering. This is more or less a boosted IC power supply, the discrete transistors on the backside provide most of the heavy current and the IC sees lower voltages and current to keep the chip from melting down.

Prime computing regulator module, 1980-81

The date codes for the parts on this show it was made in the early 80s but it is typical of 70s construction. The most notable thing is the natural fiberglass PCB, the green coating on the newer ones are a soldermask that is typical now, but in the 70s it wasn't used typically. This also has only thru hole components and a plastic DIP packaged uA723 regulator IC, designed by Bob Widlar for Fairchild. If you aren't familiar with Bob Widlar check him out, he was one of the most important early IC designers, he designed the uA709, the predecessor of the famous uA741 and a lot of other early production ICs. This design uses 2 2N3055 NPNs in parallel for the pass devices, each on an individual vertically finned heatsink.

RCA BA-7 Modular Power Supply, 1961

This is an example of an early solid state regulated supply using germanium transistors. The pass device is on a seperate heatsink and the pre-driver device is mounted directly to the chassis. The whole thing is a swappable plug-in module for a broadcast console, if the power supply were to fail on-air it could be pulled out and a new one plugged in within a few seconds, using the blue a blind-mating connector. The regulator signal electronics are on the small card, a few metal can transistors, resistors and some caps. The bottom shows the module wiring harness, done in the old style with lacing tape.

Unregulated Tube HiFi power supply, ca. 1950s

This is a pull from a console with a separate power supply and amp chassis. This is fairly typical of an unregulated tube rectified supply from the 50s or 60s, where the tube rectifier output is filtered by the capacitors and sent to the power amp. The heater supply is unfiltered 6.3VAC.