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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Some in depth Sony troubleshooting
If anyone is REAL bored maybe you could print this out, have a look at the
schematic at (pdf) at http://mywebpages.comcast.net/dharp/.../STR_DE515.pdf . It's the closest I can find to my str-se501 - the amplifier section is real close to what I have. See page 2 - at about G21. [All 5 of my ch. amps are like the top three - I don't have IC601 or IC651] Here's the deal: 1. It goes into protect mode - duh.... 2. All the speaker relays for each channel are energized. 3. Center channel is reading full supply voltage (sum of B+ and B- vs. just B+ or B- like all the other channels) on each of its output transistors from collector to base! The other channels have near zero vdc on the base and B+ or B- from base to collector. Getting B+ to the base of Q553 and B- to the base of Q554). Also, output xistor resistances different than other four channels. 4. Removed both center ch transistors. Still goes into protect mode. Traced where opposite supply voltages on the bases back to STL350-230 center channel driver IC. The other 4 channels all read the same and have identical static ckt. resistances - they are driven from uPC2581 driver ICs. Probably explains why center ch. reading different resistances than other four. 5. Removed the STK350-230 center ch. driver IC. No more weird voltage readings at the output xistors' solder points. On the STK350-230 IC I was getting B+ on pin 6 (+VEOUT) to the base of the Q553 and B- on pin 5 (-VEOUT) to the base of the Q554 which seems crap to me - maybe I'm wrong. Anyway, it still goes into protect mode. 6. Can't find anything else that doesn't seem right on any of the channels. Question: 1. Any brilliant insights into this? 2. If it goes into protect mode, shouldn't at least one of the channel's amp over load detect transistors (like Q570) be turned on and inhibit that amp's associated speaker relay? 3. Down at R6 (the signals to the display board) it seems to get its "protect in" signal (24) from the "OC Offset DET" (overcurrent detector?) at D25. It looks to me like this monitors each channel's over load detectors so again, if in protect mode, shouldn't at least one channel's overload detector be turned? 4. Do I have to do something special to reset protect mode other than power down and back up? thanks, Perion |
#2
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The amplifier is going in to protect mode, because one or more of the
output devices is shorted, or biased to pull too much current, and or there is DC at the output. You will have to change the output devices, and their associated drivers to verify this. Driver transistors can be easily checked. Usually in these amplifiers the driver and pre-driver stages are DC coupled. Check in the schematic to know for sure. -- Jerry G. ====== "Perion" wrote in message ... If anyone is REAL bored maybe you could print this out, have a look at the schematic at (pdf) at http://mywebpages.comcast.net/dharp/.../STR_DE515.pdf . It's the closest I can find to my str-se501 - the amplifier section is real close to what I have. See page 2 - at about G21. [All 5 of my ch. amps are like the top three - I don't have IC601 or IC651] Here's the deal: 1. It goes into protect mode - duh.... 2. All the speaker relays for each channel are energized. 3. Center channel is reading full supply voltage (sum of B+ and B- vs. just B+ or B- like all the other channels) on each of its output transistors from collector to base! The other channels have near zero vdc on the base and B+ or B- from base to collector. Getting B+ to the base of Q553 and B- to the base of Q554). Also, output xistor resistances different than other four channels. 4. Removed both center ch transistors. Still goes into protect mode. Traced where opposite supply voltages on the bases back to STL350-230 center channel driver IC. The other 4 channels all read the same and have identical static ckt. resistances - they are driven from uPC2581 driver ICs. Probably explains why center ch. reading different resistances than other four. 5. Removed the STK350-230 center ch. driver IC. No more weird voltage readings at the output xistors' solder points. On the STK350-230 IC I was getting B+ on pin 6 (+VEOUT) to the base of the Q553 and B- on pin 5 (-VEOUT) to the base of the Q554 which seems crap to me - maybe I'm wrong. Anyway, it still goes into protect mode. 6. Can't find anything else that doesn't seem right on any of the channels. Question: 1. Any brilliant insights into this? 2. If it goes into protect mode, shouldn't at least one of the channel's amp over load detect transistors (like Q570) be turned on and inhibit that amp's associated speaker relay? 3. Down at R6 (the signals to the display board) it seems to get its "protect in" signal (24) from the "OC Offset DET" (overcurrent detector?) at D25. It looks to me like this monitors each channel's over load detectors so again, if in protect mode, shouldn't at least one channel's overload detector be turned? 4. Do I have to do something special to reset protect mode other than power down and back up? thanks, Perion |
#3
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Unlike another reply here, don't replace the outputs unless they are
shorted, which they are not. Replace the STK350-230. Common problem. There may be another issue with the protect circuit if it's not protecting when it should. Mark Z. "Perion" wrote in message ... If anyone is REAL bored maybe you could print this out, have a look at the schematic at (pdf) at http://mywebpages.comcast.net/dharp/.../STR_DE515.pdf . It's the closest I can find to my str-se501 - the amplifier section is real close to what I have. See page 2 - at about G21. [All 5 of my ch. amps are like the top three - I don't have IC601 or IC651] Here's the deal: 1. It goes into protect mode - duh.... 2. All the speaker relays for each channel are energized. 3. Center channel is reading full supply voltage (sum of B+ and B- vs. just B+ or B- like all the other channels) on each of its output transistors from collector to base! The other channels have near zero vdc on the base and B+ or B- from base to collector. Getting B+ to the base of Q553 and B- to the base of Q554). Also, output xistor resistances different than other four channels. 4. Removed both center ch transistors. Still goes into protect mode. Traced where opposite supply voltages on the bases back to STL350-230 center channel driver IC. The other 4 channels all read the same and have identical static ckt. resistances - they are driven from uPC2581 driver ICs. Probably explains why center ch. reading different resistances than other four. 5. Removed the STK350-230 center ch. driver IC. No more weird voltage readings at the output xistors' solder points. On the STK350-230 IC I was getting B+ on pin 6 (+VEOUT) to the base of the Q553 and B- on pin 5 (-VEOUT) to the base of the Q554 which seems crap to me - maybe I'm wrong. Anyway, it still goes into protect mode. 6. Can't find anything else that doesn't seem right on any of the channels. Question: 1. Any brilliant insights into this? 2. If it goes into protect mode, shouldn't at least one of the channel's amp over load detect transistors (like Q570) be turned on and inhibit that amp's associated speaker relay? 3. Down at R6 (the signals to the display board) it seems to get its "protect in" signal (24) from the "OC Offset DET" (overcurrent detector?) at D25. It looks to me like this monitors each channel's over load detectors so again, if in protect mode, shouldn't at least one channel's overload detector be turned? 4. Do I have to do something special to reset protect mode other than power down and back up? thanks, Perion |
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