I've got a 25-diode 3-bit adder designed, but I haven't been able to test it at the system clock because I blew up my function generator's 50-/600-ohm output stage while measuring a 2N2222 switching speed (one of the hazards of testing with non-standard logic levels).

I've repaired most of the output stage, only two 1/4W resistors in the emitter followers were so toasted I have no idea what their original values might have been (they were charred, as was the circuit board underneath). I have to trace out the schematic and figure out what their values should be.

-Bobby