"Mark D. Zacharias" wrote in message
. ..
Dave wrote:
You can swap Q405 and Q406 and see if the problem moves to the other
channel. Resistor R417 (560 ohm) can be checked in circuit. R405, a 68K,
would probably need to be checked out-of-circuit. Experience tells me that
high-value resistors can change value or go open-circuit for no good
reason. Worth keeping in the back of your mind sometimes as you're
troubleshooting problems such as this.

R417 and R418 both test around 560 in circuit

R405 and R406 both test 66k in circuit

I'll try swapping Q405 and Q406 and see if the problem follows the
transistor. I found them relatively close (4 hour drive) in stock, or I can
order them in to my local supplier and wait a couple of days/weeks to
receive. How many do you think I'd have to order to find a pair with DC
gain matched to within, say, 15%? The 2SC2603 crosses to NTE289, which is
available as NTE289AMP, a matched pair for use in amplifiers...

For sure Q405 is not turning on. I watched the output of Q406 and, about 5
seconds after turning power on, it goes from -0.4 to -7.1V. Q405 just stays
at -0.4V.

Dave