STR-DE975 center channel problem

speekergeek · 11th June 2005, 05:29 PM

Hi all, I have had an intermittent problem with my center channel on my sony reciever since about a year ago. I am a sony authorized servicer so i have the schematic. I don't have much audio experience, mostly video so i am fishing for help here. the center channel uses a STK-350-230 as a mono amp for the signal, where it gets split into 2 halves of a waveform and sent to a booster (MN2488+MP1620) circuit.
The problem i have is during loud passages (in the vocal range only i hae noticed) it sounds like it may be getting full saturation and full cutoff, like a harmonic buzz. I totally thought it was my speaker because it was a crap speaker. but now with new speakers it still does it. any help is appreciated, i may be able to send you a page from the service manual to help nless you got it already.

thnx, mike

Netlist · 11th June 2005, 05:58 PM

Mike,
Try replacing the STK.
The problem is that the output transistors are incorrectly biased.
Let us know if it solved the problem.

/Hugo

11th June 2005, 05:29 PM	#1
speekergeek diyAudio Member Join Date: Oct 2003 Location: santa rosa	STR-DE975 center channel problem Hi all, I have had an intermittent problem with my center channel on my sony reciever since about a year ago. I am a sony authorized servicer so i have the schematic. I don't have much audio experience, mostly video so i am fishing for help here. the center channel uses a STK-350-230 as a mono amp for the signal, where it gets split into 2 halves of a waveform and sent to a booster (MN2488+MP1620) circuit. The problem i have is during loud passages (in the vocal range only i hae noticed) it sounds like it may be getting full saturation and full cutoff, like a harmonic buzz. I totally thought it was my speaker because it was a crap speaker. but now with new speakers it still does it. any help is appreciated, i may be able to send you a page from the service manual to help nless you got it already. thnx, mike

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11th June 2005, 05:58 PM	#2
Netlist diyAudio Moderator Emeritus Join Date: Jan 2003	Mike, Try replacing the STK. The problem is that the output transistors are incorrectly biased. Let us know if it solved the problem. /Hugo