So there is no transistor in the drive circuit?
I see the transformer is being driven from pin 12 of the 494.I guess that is why it is operating at a high temperature than other amps.I pull the FETs but no change.
I see the transformer is being driven from pin 12 of the 494.I guess that is why it is operating at a high temperature than other amps.I pull the FETs but no change.
I don't remember seeing any other of this type of amp (with a driver transformer) that drove it directly from the 494 but if that what you have, it could be the reason that the IC is heating up.
It's not driven from pin 12. That's the supply pin for the IC logic. It's driven from 8/11 or 9/10.
It's not driven from pin 12. That's the supply pin for the IC logic. It's driven from 8/11 or 9/10.
Post a photo of the drive signal with the scope set to 10us and 5v/div. USe DC coupling and align the trace to the reference line on the display.
I think the first image is OK but the scope isn't triggering as it should. Try adjusting the trigger level.
The gate should swing about 12v above and below the source leg.
The gate should swing about 12v above and below the source leg.
I got the IC to run cooler by changing the PS FETs.The FETs the previous tech used was not a good sub.I drop 50n06 in there and all is fine now.
I didn't see it earlier but I wanted a 10uS timebase and you posted a 5uS. That would make the frequency higher than I'd expect. That could be the cause of the heating with the other FETs.
Calculate the oscillation frequency from the installed components to see if it's what it should be.
Calculate the oscillation frequency from the installed components to see if it's what it should be.