I am currently fighting an amp that has a MOSFET output stage.
A Professional Music Power amp used by Music bands.
This thing is a Chinese design, this I can tell pretty easily.
I am having a hard time finding a fault.
I did fix it once, but the owner took the cover and did some thing, what I dunno, he called and said fire and smoke came out form the board.
Previously a SMD resistor was blown in the driver stage. This time another resistor was blown, replacing it is causing another to heat up.
The topology is AB, since it uses MOSFET pairs at the output. But they are rather small for a professional grade Power amp. I mean it uses the IRF640. TO-220 packages.
Funny thing is, this thing uses 3 opto couplers with in the driver and pre-drive stage. I have never seen any one using opto's in an audio amp.
Does any one have any schema's of this kind, that I might refer to.....
Problem is that this bloody thing is driving me nuts. I just can't seem to find a faulty component. I have been at it non stop for more than a night...
I do have pictures, if any one likes to see it, just ask..Since I am fighting this thing right now I cannot edit and upload the pics.
The reason for asking this is a funny one.
Now I know how opto's work. But this one is a dooozy....
I measured 18V across the input of one in circuit, which lead me to believe that the LED would have definitely be blown, so I took it out but the diode check says it's OK.
What Gives..........
A Professional Music Power amp used by Music bands.
This thing is a Chinese design, this I can tell pretty easily.
I am having a hard time finding a fault.
I did fix it once, but the owner took the cover and did some thing, what I dunno, he called and said fire and smoke came out form the board.
Previously a SMD resistor was blown in the driver stage. This time another resistor was blown, replacing it is causing another to heat up.
The topology is AB, since it uses MOSFET pairs at the output. But they are rather small for a professional grade Power amp. I mean it uses the IRF640. TO-220 packages.
Funny thing is, this thing uses 3 opto couplers with in the driver and pre-drive stage. I have never seen any one using opto's in an audio amp.
Does any one have any schema's of this kind, that I might refer to.....
Problem is that this bloody thing is driving me nuts. I just can't seem to find a faulty component. I have been at it non stop for more than a night...
I do have pictures, if any one likes to see it, just ask..Since I am fighting this thing right now I cannot edit and upload the pics.
The reason for asking this is a funny one.
Now I know how opto's work. But this one is a dooozy....
I measured 18V across the input of one in circuit, which lead me to believe that the LED would have definitely be blown, so I took it out but the diode check says it's OK.
What Gives..........
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