Hi all.
Long time lurker - first time poster.
I have a pure stock Yamaha M80 that has worked flawlessly for years. Driving a pair of B&W 803 matrix s2.
Suddenly, we have a noticeable noise floor in the form of low level white noise or hiss.
The hiss is louder in one channel or the other when adjusting the level control for that channel – similar to wiper noise but very consistent and on both controls.
The temporary increase in hiss is greater the faster the knob is turned and can put the amp into protection briefly.
Setting either control higher than 45% triggers the amp protection until the level is reduced below that threshold.
The amp still plays – as long as the level controls are left below that protection threshold.
Does this sound like a filter cap issue?
Deeply appreciation any suggestions where I should start the diagnostic journey.
Long time lurker - first time poster.
I have a pure stock Yamaha M80 that has worked flawlessly for years. Driving a pair of B&W 803 matrix s2.
Suddenly, we have a noticeable noise floor in the form of low level white noise or hiss.
The hiss is louder in one channel or the other when adjusting the level control for that channel – similar to wiper noise but very consistent and on both controls.
The temporary increase in hiss is greater the faster the knob is turned and can put the amp into protection briefly.
Setting either control higher than 45% triggers the amp protection until the level is reduced below that threshold.
The amp still plays – as long as the level controls are left below that protection threshold.
Does this sound like a filter cap issue?
Deeply appreciation any suggestions where I should start the diagnostic journey.
hello.
i have no schematic here on hand.........
but if both channels are affected the flaw could sit in the power supply unit.
first i would clean all contacts (fuseholders,........)
after this i would look for a broken soldering point/pcb copper line......
i have no schematic here on hand.........
but if both channels are affected the flaw could sit in the power supply unit.
first i would clean all contacts (fuseholders,........)
after this i would look for a broken soldering point/pcb copper line......
Thanks for the pointers mjf - I'll start there.
I did manage to find a service manual thanks to other posts in this forum.
I did manage to find a service manual thanks to other posts in this forum.
thanks for the offer Alex - I downloaded one already.
I'm afraid I don't have a scope to look for output oscillation.
I'm afraid I don't have a scope to look for output oscillation.
one of a very common way to fault finding that originates from tv repairs is the freezer spray ..
had similar issues on the head preamp of a reel and age was the main issue i started by replacing small capacitors ...in the preamp area ... then form a voltage aspect all was fine in the preamp then i thought about freezing the transistors ....Oooops after i freeze the one transistor hiss was gone ....replaced all of them and that's it
Often in ltp pairs manufacturers run the semis on the edge to get best results and this can cause such an issue .... combine this with the momentary click of protection ( which obviously comes from Dc in the output ...which obviously come from balance issues ....which obviously means that LTP is the place to start)
happy regards
sakis
had similar issues on the head preamp of a reel and age was the main issue i started by replacing small capacitors ...in the preamp area ... then form a voltage aspect all was fine in the preamp then i thought about freezing the transistors ....Oooops after i freeze the one transistor hiss was gone ....replaced all of them and that's it
Often in ltp pairs manufacturers run the semis on the edge to get best results and this can cause such an issue .... combine this with the momentary click of protection ( which obviously comes from Dc in the output ...which obviously come from balance issues ....which obviously means that LTP is the place to start)
happy regards
sakis
I think all the hissing and protect problems are because the amp is female.... and it's schematic cannot be understood.....did you forget a birthday or something???
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