When I started making Tubelab SE amplifiers I realized that testing newly built PC boards was a pain. I would drag out a set of transformers, tack solder the wires to the PC board, then test everything, only to disconnect the transformers and put them away. People assembling amplifiers also told me that they would like a better way to hook up the transformers. I decided to use connectors on my latest design. That worked out well so far.
I am always trying experiments with different transformers, tubes, chokes and so forth. The connectors made it easier to do this. I have ordered a batch of PC boards for this amp and I would like to have a way to test a newly built board without the setup time. I started thinking…………
Then I thought of a way that I could test a board, or an OPT, or a power transformer, or choke, with only a screwdriver. So, I built it!
It is ugly, so call it a breadboard, or a test fixture. The pins that are used to plug into the screw terminals on the PC board were saved (for a long time) from my earlier life making SS-50 buss computers. The “euro – style” terminal strips are from All Electronics (also available at Radio Shack). Each OPT and the power transformer are connected using one of these.
It is not even finished yet, and I have already cranked through about 5 different sets of OPT’s and 3 power transformers. I have several more waiting to be tested. After playing with it this weekend, I added the switch panel. It is not all connected up yet, but I will be able to switch from UL to triode, turn on or off the cathode feedback, switch from tube to SS rectifier, and go into standby.
After completing the first of the new PC boards, I put one to the test. It took 5 minutes to change the board.