Lab Power Supply.
Project Key Data
- Description: A 0-30V/2A Power Supply with Controllable Current Limiting.
- Started: XXX
- Releases:
- No formal releases.
- Status: [maintained]
- Development:
- Instruments:
- JDJ-30V-2A
- Units:
- JDJ-30V-2A
20210227 Note
Built after an article in Hobbit (or one of its predecessors). I recall that it featured two series-transistors, for voltage and current control, respectively. I used this unit for many years, if not decades… It actually survived a couple of re-casings.
[20210303] Retracing the Origins
Today I took several pictures of the inside of the single unit I have of this design, just to figure out what its origins are.
The inside looks like this:
My first impression was that with just some minor efforts, the inside of the unit could be used as a ballroom or playground for, say, mice. Oh boy, so much space… Other than that, not many surprises in terms of components or layout for a linear power supply. The heat sink at the bottom of the picture serves the two series transistors; one for voltage regulation and one for current (I did remember that was quite remarkable in the design). However, the heat sink also cools a third component; a component that I failed to take pictures of (a diode for temperature sensing perhaps?).
The real purpose of this exercise was to figure out the source of the design. This becomes clear from the bottom side of the main PCB:
Most likely, the PCB layout was drawn by hand using an etch-resistant pen. After etching (with irontrichloride) and cleaning the board, I would typically solder all traces in order to reduce the impact of “undercut”. (I’m not really 100% sure about terminology here; the Dutch equivalent is “onder-etsen”: the process of losing traces due to attacks on their vertical sides from etching residue.)
Zooming in onto the lowest half of the PCB we clearly find the HB 4-83 marking. So, as I already suspected, this is a design described in the Dutch hobby-electronics magazine “Hobbit”, number 4 of 1983. A link to the article in that magazine (in Dutch) was quickly found here.
Other noteworthy observations [see pictures for details]:
- The series transistors are (most likely) TIP2955.
- If the marking on one of the TIP2955’s is a date code, this dates the construction of the unit to September 1984 at the earliest. This is actually later than I expected, but it makes sense in view of the project description in Hobbit.
- The transformer is (of course) an Amplimo, type 31012/R072, 2x12V/3.33A. Good to see I already overdimensioned by design in those days.
- I measured the dimensions of the Kyoritsu V-meter in the front panel. The drilling hole pattern for the mounting screws is rectangular (~48mm), even though the user-facing part of the meter is not (~66mmx60mm). The A-meter that was once next to it apparently had the same dimensions.
