The case is an old PA amplifier that I stripped out, modified, and painted with hammered paint.
#2n3055 pass transistor schematic full#
Here is a full view of the inside of my linear power supply. All my vanity went into how it looked on the outside, you see. I’m not really proud of the way this looks – really should have used at least a screw terminal for the connecting wires – but, it works and I never expected to have to show it to anyone.
#2n3055 pass transistor schematic install#
Unfortunately, there is the risk of the exposed leads touching something they aren’t supposed to, which I think was the downfall of my initial install of the 2N3055 transistors. I’ve also always liked the vertical mounting of axial resistors as seen in some older equipment and inexpensive consumer equipment. The terminal strips I use to mount the filtering capacitor for the logic supply are something I learned from my antique radio restoration. As you can see, pretty old fashioned construction. Here is the simple circuit board for the LM723 and jellybeans. This explains the more mangled state of the buses in the final mounted picture. While robust, this proved to be a terrible pain when I blew out my first set of transistors during testing. I used 12 gauge solid core wire for all high current buses, and as you can see I directly soldered to the packages of the transistors. It was one of those square packages with the screw hole for easy mounting. For filtering there was 8000uF of electrolytes, and the rectifier was mounted directly to the heatsink. The above picture shows the assembly in testing, while the lower pictures shows it installed inside my case. Yes, there were mica insulators between the TO-3s and the heatsink, so the chassis was not at potential. It’s nice working with these old TO-3 packages, not so nice to find mounting gear for them these days. I bought an old audio amplifier heatsink on eBay, which had the TO-3 package mounts. The LM723 takes feedback on pin 4 through the voltage divider, and the BD139 drive the bases of the NPNs.Īs you can see, I took heat dissipation pretty seriously in my design. The only trick might be the balancing resistors of the four 3055 NPNs, which requires high dissipation wire wound resistors. The schematic is taken from another website, but the design of a 723 linear supply is pretty straightforward. All it needed was a huge heatsink, some heavy duty current buses, and a presentable case. While the 723 is rather long in the tooth and has poor current control, and the 2N30s levels of gain, I didn’t think there was a real need to go for high tech in my linear power supply.
The LM723 and the 2N3055 are some old school components that have been in production since the 1970s. Even a cheap Chinese power supply was out of my price league, with a dual tracking 0-40V 0-10A supply going for about $300. For one thing, they were all all at least 40lbs for anything around the power levels I was looking for, (I was working with induction heating at the time and was looking for 500W+) while anything that was even near reasonable to ship was a puny 0-12V 0-5A job. I needed a suitable low voltage power supply for projects, and I was getting disillusioned with the prospects of nabbing a suitable one on eBay. LM723 + 2N3055 Pass Transistor Linear Power Supply: 0-40V DC 0-20A
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