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Yesterday, 07:34 PM
Hi Steve
With a 1M pot and R23=36k and R5=330k Vout max is low by about 8V.
With R5=313k Vout max is low by 4V.
If R5=346k Vout max loses 23V.
I haven't found the fixed resistors to be off by their limit, but there are a lot of parameter spreads to deal with. For one thing, I don't have a model for the FQU and have used something that is not as similar gate-wise as I think. Gate threshold voltages on mosfets have a wide spread, so you will have to tinker with the fixed Rs to get the loss at Vout max down to where it should be.
One thing you might be able to control is how hot the mosfets get. Is there airflow over the chassis position where the board is mounted? If not, add a low-speed fan to move air past the tubes and out the back of the cabinet.
6Vac >> bridge >> 10mF cap >> 8Vdc to 12Vdc fan
Have fun
With a 1M pot and R23=36k and R5=330k Vout max is low by about 8V.
With R5=313k Vout max is low by 4V.
If R5=346k Vout max loses 23V.
I haven't found the fixed resistors to be off by their limit, but there are a lot of parameter spreads to deal with. For one thing, I don't have a model for the FQU and have used something that is not as similar gate-wise as I think. Gate threshold voltages on mosfets have a wide spread, so you will have to tinker with the fixed Rs to get the loss at Vout max down to where it should be.
One thing you might be able to control is how hot the mosfets get. Is there airflow over the chassis position where the board is mounted? If not, add a low-speed fan to move air past the tubes and out the back of the cabinet.
6Vac >> bridge >> 10mF cap >> 8Vdc to 12Vdc fan
Have fun
