Help Please Denon AVR receiver

[Bargainhunter]

Hi,

I have a Denon AVR-4520CI for repair.  One Output transistor was shorted.  I replaced both DHCT-C3 and DHCT-A3.  Both pair of .22 ohm emiter resistors are okay.  Before I returned the Amp Board to the receiver, I tested both the DHCT-C3 and the DHCT-A3 with a semiconductor analyzer against another pair in one of the good Amp Boards.  The DHCT-C3 and the DHCT-A3 that I replaced shows a collector leakage Icbo of 4.7 ua versis 1.3 ua on the other boards.  I have attached the schematic (FHL board).  Could anyone tell me why I have 3.5x higher leakage?  The other resistors and transistors check okay in circuit. Could D506 be the problem?

Thank you,
Chuck

[singapol]

If you have replaced with the same identical parts then maybe the new batches have different leakage current.Do remember you are measuring in-circuit when a more accurate measurement
is out of circuit. I suspect the difference may not matter.BTW DHCT A3/C3 are darlington transistors.

If you suspect D506 which is a zener then you should also check corresponding zener D508. Also check the 2 diodes connected to them.You can also check Z501 which symbol look like a thermistor.

Also check D503 (zener symbol?) and diode D510.

[Bargainhunter]

Thank you for your help.
I tested both before I soldered them in circuit - out of circuit there was zero leakage.  Since the components are SMD's and my vision is not what it used to be, I wanted to eliminate as much soldering as possible.  The diodes test okay in circuit but to be sure, I will try to lift one leg of the diodes or thermister if possible to test out of circuit.

Chuck