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optonica 5605 stuck in protection

enedwaith

enedwaith

New Member
https://www.hifiengine.com/manual_library/sharp-optonica/sa-5606.shtml

cannot find manual for 5605 but i believe the 5606 runs similar specifications. the unit arrived today and will not move past the protection - light stays red, never clicks to green. checking the DC offset, seems to be.. variable.. -1.2mv in A speaker output, +300mv in C speaker output? i'll let the amp settle and check again in a while.

i do not have much experience in electrical service, but i have a decent soldering station, multimeter, and i like to read. please let me know if you have any ideas on where to begin troubleshooting! (i haven't yet opened up the unit to check fuses, i'll have time to spend in a couple hours from this post)

cheers


quick update: all speaker outputs settle at -1.2mv from my multimeter, i think the +300 popped up when i was switching the output selection toggle
 
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Since the receiver is in protection mode there is nothing to measure at the speaker terminals, the speaker relay is not energized. To measure the DC offset you'll have to measure before the relay, the easiest place would the emitter resistors for the output transistors. Anything more than a few mv would indicate a problem in that channel. If those voltages look OK it may just be fault in the protection circuit itself. It provides protection at turn on and off, DC protection (that's the DC offset you're trying to measure), thermal protection. Hopefully the 5606 manual is close to the 5605.

Craig
 
Test the the DC-offset at test points TP-503 Left channel and TP-504, as IIwhtt said, if the protection relay isn't engaging the speaker terminalls will be disconnected from the amp board, differences between the 5605 and the 5606 seem to just be color ones a black face the others a silver face, I would test the output transistors, chances are one or both channel have shorted outputs.
 
enedwaith said:
https://www.hifiengine.com/manual_library/sharp-optonica/sa-5606.shtml

cannot find manual for 5605 but i believe the 5606 runs similar specifications. the unit arrived today and will not move past the protection - light stays red, never clicks to green. checking the DC offset, seems to be.. variable.. -1.2mv in A speaker output, +300mv in C speaker output? i'll let the amp settle and check again in a while.

i do not have much experience in electrical service, but i have a decent soldering station, multimeter, and i like to read. please let me know if you have any ideas on where to begin troubleshooting! (i haven't yet opened up the unit to check fuses, i'll have time to spend in a couple hours from this post)

cheers


quick update: all speaker outputs settle at -1.2mv from my multimeter, i think the +300 popped up when i was switching the output selection toggle
Click to expand...

Eastham said:
Test the the DC-offset at test points TP-503 Left channel and TP-504, as IIwhtt said, if the protection relay isn't engaging the speaker terminalls will be disconnected from the amp board, differences between the 5605 and the 5606 seem to just be color ones a black face the others a silver face, I would test the output transistors, chances are one or both channel have shorted outputs.
Click to expand...

i see the TP-503 in the schematics, what would a test point look like visually? don't want to totally disassemble the unit just yet.

thanks
 
enedwaith said:
i see the TP-503 in the schematics, what would a test point look like visually? don't want to totally disassemble the unit just yet.

thanks
Click to expand...

A little metal post sticking up off the board, should be labeled on the board as TP-503
 
TP = "test point" VR= variable resistor or the bias adjust. (sometimes amp sm's have dc 'offset' pots, too..)
If not sure pics would help as 'Eastham' noted!!

very short Pins, a pair or one for each channel or could be two sets for each channel. Do not short them! use isolated connects etc. these are not connected to ground for idle bias adjust. i.e. connecting neg to chassis ground.
 
Binkman said:
TP = "test point" VR= variable resistor or the bias adjust. (sometimes amp sm's have dc 'offset' pots, too..)
If not sure pics would help as 'Eastham' noted!!

very short Pins, a pair or one for each channel or could be two sets for each channel. Do not short them! use isolated connects etc. these are not connected to ground for idle bias adjust. i.e. connecting neg to chassis ground.
Click to expand...

so to clarify - red test lead to the TP, black lead to chassis ground?
 
Rail voltages can be measured at the output transistor collectors or at the main largest filter capacitors in the power supply.
 
so, i attach red test lead to the emitter terminal of a transistor in the power supply, and the black to ground?
 
enedwaith said:
so, i attach red test lead to the emitter terminal of a transistor in the power supply, and the black to ground?
Click to expand...
Correct. But.. there are 4 output transistors probably fastened to a large heatsink. Black test lead connected to chassis ground . Red test probe to the case of those 4 output transistors one at a time. Do not let the probe slip and short the case to the heatsink(ground ! ).
At this time I'm not concerned with a transistor in the power supply.
 
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