Sony STR-DE615 : Indicates PROTECTOR

[Russ Wright]

Recieved with the main fuse blown. No text display.

Replaced MN2488 (Q556) and MP1620 (Q557)outputs plus 2SA988 (Q558)

Now the unit indicates PROTECTOR after a few seconds, What may I have
missed. Any suggestions ,

Thank You


Russ

 

[Mark D. Zacharias]

Open resistors, bad 2SA988 protection "gate" transistors, open emitter
resistor, DC offset due to bad driver IC, who knows?

Mark Z.

 

[Andy Cuffe]

Recieved with the main fuse blown. No text display.

Replaced MN2488 (Q556) and MP1620 (Q557)outputs plus 2SA988 (Q558)

Now the unit indicates PROTECTOR after a few seconds, What may I have
missed. Any suggestions ,

Thank You

Russ

First thing to do is make some measurements to find out what's
happening. Chances are you'll see a large DC offset on the emitter
resistors. In any amp, this is due to any number of problems such as
open resistors, or bad driver transistors and ICs. Use the good channel
as a reference to see where the DC offset is coming from, or to swap
driver ICs and other parts.

 

[Andy Cuffe]

Recieved with the main fuse blown. No text display.

Replaced MN2488 (Q556) and MP1620 (Q557)outputs plus 2SA988 (Q558)

Now the unit indicates PROTECTOR after a few seconds, What may I have
missed. Any suggestions ,

Thank You

Russ

Do you get a raster when you turn up the G2 control?

 

[Leonard Caillouet]

Did the new transistors short? Did you check the emitter resistor? Did it
run with the transistors out of the circuit? Did you resolder several dozen
bad solder joints?

Leonard Caillouet

 

[Russ Wright]

As suggested by others, I have found an open Emitter resister , that is used
with the shorted output transistors that I changed earlier. I will replace
this, I also found doing some web searches about insuring ALL ground screws
are in place.
I have not resoldered any "cold solder joints" As I was not looking that
way, something else to check

Thanks , I will follow up as I go.

Russ

Did the new transistors short? Did you check the emitter resistor? Did it
run with the transistors out of the circuit? Did you resolder several dozen
bad solder joints?

Leonard Caillouet