Strange PL 400 outputs transistor failure

[laatsch55]

It could be your bias tranny is losing gain, getting tired and just not that useful anymore.

 

[wattsabundant]

In case it's not obvious, a Darlington is two cascaded transistors (in series sort of) to get greater gain. A gain of more than 1000 is not uncommon. When using a meter to check transistors, the diode range puts out a current and the meter reads the voltage drop across the junction when it conducts. On the resistance range, the meter only puts out around 200mv which isn't enough for the junction to conduct. The XPL910's do have resistors across the B-E junctions. The resistors are not traditional resistors but are manufactured as part of the die.

 

[laatsch55]

I have had youngsters that have never seen a LP or reel to reel or vacuum tube with their eerie glow taking pictures of my setup with their smartphones after they were blown away by the volume of music and vibration of their bodies. I know exactly what your talking about.

I've sent a few of those youngins out of the mancave in a state of awe and shock. The paperboy will never be the same, nor the loud car audio sloppy bass kid. He now knows what bass should sound like.