Don't you just hate it when you're working on some battery powered equipment which has a power jack but you don't have the right power pack to suit it, and using crock clips connected to a bench PSU don't really seem to be a wonderful solution? Well today I have had a number of items delivered from Amazon and I already had a Universal Mains Adaptor by Uniross (Uni 1200R), offering output voltages of 1.5, 3, 4.5, 6, 7.5, 9 and 12v @1200mA and a lead with a 2 pin socket to accept a number of adaptors and depending on which way you connected the pins, you could reverse the polarity, and these adaptors are never the best fitting of things and often come disconnected.
I decided to remove the that stupid socket and fit a DC Barrel plug, 5.5 x 2.5mm to plug into a kit of adaptors from Amazon (38 of them) which have a 5.5 x 2.1mm socket in their base which means that the polarity cannot be changed. To over come this I ordered some CCTV connectors, which are designed to take 2 core cable and terminate in screw terminals. On the other end of these adaptors is either a plug or socket of the same type, 5.5 x 2.1mm DC power. These now enable me to make up some short polarity changers to enable the odd ball items that need a centre pin negative supply to be accommodated, regardless of its type of connector. An example of this is Hacker radios which use negative centre pins, some Casio desk calculators and maybe some Roberts radios as well?
Because the CCTV power connectors accept cable to terminals on one side, I have made some leads with 4mm banana plugs and these can then be plugged into the bench power supplies which can be adjusted to suit voltages beyond the scope of the Uniross unit, such as 19V for laptops etc.
The polarity changer could dispense with the wire and just have 2 short component legs as the interconnection, back to back.