Laboratory
DC Power Supply
Universal Adapter
Introduction/Why
As a electronics technician, retro video game console hardware modder, and hobbyist circuit builder, over the years I have acquired a comprehensive electronics and hardware toolbox for the garage. One tool that I've always wanted for my electronics toolbox is a lab bench DC power supply. Often times when I pickup used electronic gadgets from thrift stores, fleatiques, or garage/yard sales the devices have DC power jacks to power them and are supposed to come with a matching power supply. Unfortunately, many times the devices aren't sold with the matching power supplies, and thus I am not able to test or power on the devices. A lab bench DC power supply would also be nice for powering any active circuits I design on breadboard or PCB prototypes.
A DC Barrel Jack and a power supply
Using a laboratory DC power supply (with variable voltage and variable current), I would be able to dial in the correct, constant voltage and maximum current to power my devices with missing power supplies. I would need to build a universal adapter to power on the DC power jack devices and interchange the DC barrel jack tips. I have a universal DC power supply in my electronics toolbox with interchangeable DC barrel jack tips, but the variable voltage range is small and the maximum current is limited to only a paltry 300mA. This power supply is fine for powering simple electronics devices, but not for more complex devices such as video game consoles (like a Sega Genesis Model 1 or portable DVD player, which can require 1A and 2.2A of current respectively.)
A word about replacement DC power supplies
As a general rule, when finding a replacement DC power supply for a device, the voltage needs to be exactly the same (constant voltage), but the current supplied can be slightly above the rated specifications for the device. This is due to most electronic devices having some tolerance for the current draw on the device. It is always better to have slightly more current supplied than not enough; otherwise the device will not operate correctly. The device will draw as much current as needed during operation. The replacement power supply should also have the same polarity as the original (either center-positive, or center-negative). Center-positive means that the center pin in the DC barrel jack is positive current, while center-negative means that the center pin is negative current. The barrel inside will have the opposite current polarity.
Center-Positive vs. Center-Negative
An example of a good power supply replacement:
- Device requires a 9V 1.2A power supply (center positive)
- Replacement power supply of 9V 1.5A (center-positive) works
An example of a bad power supply replacement:
- Device requires a 9V 1.2A power supply (center positive)
- Replacement power supply of 12V 2A (center-positive) is bad
- Too much voltage (3V above rated specification)
The Vizatek Laboratory DC Power Supply (MPS-6003L-1)
Fortunately, while I was on vacation in Branson, Missouri during summer 2024, I finally stumbled across a laboratory DC Power Supply at a local thrift store. I was thrilled to find a used Vizatek Laboratory DC Power Supply (MPS-6003L-1) being sold for only $8. Considering that these units can go for $130 new this was a bargain I couldn't refuse, so I purchased it!
The Vizatek Laboratory DC Power Supply (MPS-6003L-1) is a basic, variable laboratory power supply. It is rated up to 0-60V and 0-3A. Unlike cheap Chinese laboratory DC power supplies that you can get on eBay for less than $50, the build quality of this Vizatek power supply is solid and industrial. It has a grounded 3-prong power cable to power the device, a large finned metal heat sink on the back; and positive (+), ground, and negative (-) banana plug jacks for the output power. It weighs a few pounds but the device is awesome as a laboratory power supply.
The device has 2 digital 7-segment display readouts; one for the voltage and the other for the current. Both are 3-digits displays with a decimal place indicator. The device also has 2 sets of course and fine knobs for dialing in the power parameter; one set of knobs for the voltage parameter, the other set for the current parameter. Operation of the device is basic yet simple.
The DC power supply has 2 modes of operation:
- Constant voltage
- Like a regular barrel jack DC power supply that come with electronic devices
- Voltage is constant
- Current varies during operation (up to a maximum current setting)
- Constant current
- Current is constant
- Voltage varies during operation
of simple laboratory DC power supplies
(EETechStuff)
DC Power Supply
(MPS-6003L-1)
Building the Laboratory
DC power supply
universal adapter circuit
I happen to have two spare universal DC barrel jack power supplies in my toolbox:
- Universal power supply (PH2061W)
- Found NIB at my Dad's house decades ago
- Set of interchangable DC power jack tips
- Variable voltage (1.5, 3, 4.5, 6, 7.5, 9, 12V)
- Constant current (a low 300mA)
- Radio shack power supply (273-1760)
- Goodwill thrift store find
- Interface for interchangable DC power jack tips
- Constant voltage 4.5V
- Constant current 1600mA (1.6A)
and interchangeable DC barrel jack tips
- Tools
- Vizatek Laboratory DC Power Supply (MPS-6003L-1)
- Banana to alligator power cable
- Interchangeable DC barrel jack tips
- Universal DC barrel jack interface (scrapped from Radio Shack power supply)
- Supply
- Electronics perfboard
- Male perfboard headers
- Solid-core wire
To design the universal CD barrel jack adapter for my laboratory DC power supply, first I cut off the universal DC barrel jack tip interface from the Radio Shack power supply, then I stripped the wire and tinned them with my soldering iron. I cut off a small portion of electronics perfboard to use as the circuit board. Then I soldered on a 4-pin male header (to clamp the output power from the lab DC power supply via alligator clips). The extra pins provide stability for the header row on the circuit board (vs. 2-pins), as well as some physical space to prevent the alligator clips from crossing.
I soldered the output from the male header terminals to the inputs of the universal DC barrel jack tip plug with some solid-core wire, and soldered the universal tip plug to the large strip solder pads on the perfboard. The final design doesn't look pretty, but the universal DC barrel jack adapter works and has a solid electrical connection! For a center-negative power supply, the male header pin near Terminal "N" is the negative pin, while the pin near Terminal "Q" is positive. For a center-positive power supply, just flip the pins. I colored the negative wire with black dry-erase marker.
Piece of electronics perfboard,
universal DC barrel jack plug
Final product
Universal Laboratory
DC Power Supply Adapter
Conclusion
the laboratory DC power supply
and universal adapter
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