gregmcm
Active Member
Have read a lot of threads and the protection relay kicking in seems to be a common and sometime mysterious problem on a number of Pioneer units. Wondering if anyone has had a similar experience to mine (see below) and if so were they able to identify the source of the issue.
Here is my story:
- Pioneer SX-980 - all original as far as I can tell as there are no apparent signs of any work having been done on the unit with the exception of one indicator light (Aux) having been replaced.
- unit worked but obvious signs of some bad caps on the Power Supply and at about one third volume into 8ohm speakers with Loudness engaged the protection relay would kick in. When this would happen turn the volume down and a few seconds later the unit would work fine. Replaced the 12 caps on the Power Supply board and adjusted the Center Voltage and Idle Current as per the service manual. Unit sounded better (stronger) and now can turn the volume much higher but at about two thirds volume the protection relay kicks in. Once again turn volume down and a few seconds later unit comes back on and sounds fine.
- rechecked the adjustments and all good.
- visual check of the protection circuit board and no obvious signs of problems.
Questions: has anyone had a similar experience that they have been able to solve?
-Any suggested next steps in troubleshooting to isolate the issue?
-is it worth it to change out the capacitors on the protection circuit board?
-are there any known issues with the transistors on either the Power Supply or Protection Circuit board?
PS: I have some DMM's, Capacitance checking and ESR meters plus an Oscilloscope. Thanks in advance.
Here is my story:
- Pioneer SX-980 - all original as far as I can tell as there are no apparent signs of any work having been done on the unit with the exception of one indicator light (Aux) having been replaced.
- unit worked but obvious signs of some bad caps on the Power Supply and at about one third volume into 8ohm speakers with Loudness engaged the protection relay would kick in. When this would happen turn the volume down and a few seconds later the unit would work fine. Replaced the 12 caps on the Power Supply board and adjusted the Center Voltage and Idle Current as per the service manual. Unit sounded better (stronger) and now can turn the volume much higher but at about two thirds volume the protection relay kicks in. Once again turn volume down and a few seconds later unit comes back on and sounds fine.
- rechecked the adjustments and all good.
- visual check of the protection circuit board and no obvious signs of problems.
Questions: has anyone had a similar experience that they have been able to solve?
-Any suggested next steps in troubleshooting to isolate the issue?
-is it worth it to change out the capacitors on the protection circuit board?
-are there any known issues with the transistors on either the Power Supply or Protection Circuit board?
PS: I have some DMM's, Capacitance checking and ESR meters plus an Oscilloscope. Thanks in advance.
need to figure out what is causing it, measure the DC offset of each channel. measure the power supply voltages and compare against the schematic.