P
Perion
- Jan 1, 1970
- 0
Hi
My Sony home theater str-501 is in protect mode due to internal overload. The
center channel output transistor pair reads different (ohming the junctions in
circuit) than the other four channels - all channels use the same PNP-NPN pair
type. I also noticed that after going into protect, the center channel pair
transistors had 120 vdc across two leads (one's the emitter - not sure of the
other - probably collector - haven't looked up the pinout yet) while all the
other pairs had +60 for one xistor and -60 for the same leads. I popped out the
center ch. pair - still goes into protect mode. The center ch. outputs are
driven from an stx350-??? IC - the other channels are driven from two uPC????
driver chips [don't have the numbers at the moment]. I popped out the stx350-???
but still goes into protect mode. I can't find any bad transistors (using static
diode check on Fluke), shorted caps, etc. Any ideas or does anyone have any
deeper details of typical Sony's amps?
Also, there are some tiny "biasing transistors" also pasted to the main heat
sink. What are these for and could they cause the problem? Haven't checked them
yet - wasn't time last night.
Thanks,
Perion
My Sony home theater str-501 is in protect mode due to internal overload. The
center channel output transistor pair reads different (ohming the junctions in
circuit) than the other four channels - all channels use the same PNP-NPN pair
type. I also noticed that after going into protect, the center channel pair
transistors had 120 vdc across two leads (one's the emitter - not sure of the
other - probably collector - haven't looked up the pinout yet) while all the
other pairs had +60 for one xistor and -60 for the same leads. I popped out the
center ch. pair - still goes into protect mode. The center ch. outputs are
driven from an stx350-??? IC - the other channels are driven from two uPC????
driver chips [don't have the numbers at the moment]. I popped out the stx350-???
but still goes into protect mode. I can't find any bad transistors (using static
diode check on Fluke), shorted caps, etc. Any ideas or does anyone have any
deeper details of typical Sony's amps?
Also, there are some tiny "biasing transistors" also pasted to the main heat
sink. What are these for and could they cause the problem? Haven't checked them
yet - wasn't time last night.
Thanks,
Perion