factory marks on 2N3055 power transistors

[Brian Comnes]

I noticed that the 2N3055 power transistors on the back of my Sunn Concert Bass, Concert Slave and Studio PA all have hand written marking pen annotations on them like 98 or 115. and that they all have the same rating on each unit within a number or two.

Was this some kind of matching scheme used by Sunn assemblers to match transistor output like matched tubes?

Any negative results if I match a 98 with a 115?


Any way to test or rate a new replacement 2N3055 that isn't marked?

From a confused tube-nerd
Brian

[Don T.]

Hello:
 Yes in deedee. Due to the design of the amp, matched transistors were needed because of the 50% bias of the amp. In the early days the center of the wave form (0v output) was actually half of the power supply voltage. The two transistors split the voltage by being in series, thus the need for matched gain. I believe if you have a transistor testing multimeter, you can use the HFE figure and match them that way. However asymetrical distortion can also be cool and since matched transistors don't stay that way over time maybe that is part of the "sound" we all like so well. So there you have what I remember but you might check with some "transistor head" techs to verify.
Don T.