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Sony STR-DE615 : Indicates PROTECTOR

Discussion in 'Electronic Repair' started by Russ Wright, Oct 16, 2003.

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  1. Russ Wright

    Russ Wright Guest

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

    Mark Z.
     
  3. Andy Cuffe

    Andy Cuffe Guest


    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.
     
  4. Andy Cuffe

    Andy Cuffe Guest


    Do you get a raster when you turn up the G2 control?
     
  5. 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
     
  6. Russ Wright

    Russ Wright Guest

    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


     
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