I am working on a full rebuild of a Pioneer M-22 class A power amp and have some questions that I hope someone here could shed some light on.
This amp came to me because it broke down, accordingly to the owner because he first switched on his (heavily modified) Philips CD-104, then the pre (Pioneer C-21) and only then the M-22, after which the M-22 emitted a cloud of smoke and did not come out of protection anymore.
I meanwhile traced the fault back to a blown ouput transistor, but I wonder what truth there might be in the order of switching on the devices and the risk involved of blowing an output transistor?
Specifically because there must be at least a sufficient DC protection given by the 2 pieces of 3.3uF/100mV metallized mylar capacitors that are directly below the inputs. Or do I miss something?
This amp came to me because it broke down, accordingly to the owner because he first switched on his (heavily modified) Philips CD-104, then the pre (Pioneer C-21) and only then the M-22, after which the M-22 emitted a cloud of smoke and did not come out of protection anymore.
I meanwhile traced the fault back to a blown ouput transistor, but I wonder what truth there might be in the order of switching on the devices and the risk involved of blowing an output transistor?
Specifically because there must be at least a sufficient DC protection given by the 2 pieces of 3.3uF/100mV metallized mylar capacitors that are directly below the inputs. Or do I miss something?
Download the Pioneer M-22 manuals for free - Hifi Manuals
Unfortunately VR100 and VR200 can get dirty sliders and as a consequence excess current is drawn through the output stage and that can cause issues.
Follow the circuit diagramme in the above service manual and you will find the cause and then can fix it.
Unfortunately VR100 and VR200 can get dirty sliders and as a consequence excess current is drawn through the output stage and that can cause issues.
Follow the circuit diagramme in the above service manual and you will find the cause and then can fix it.
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