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F5 pcb group buy...

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#414
Pathmark said:
ok i built second channel but same result! not sure what would cause -20 volts at output? there are not that many components to place incorrectly! any ideas?
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Confirm that the parts are the correct values. I used 0.91ohm dale mra-5's (for R11 & R12) and only checked one to confirm. Turns out one was actually 90ohm and let the smoke out of the opposite side mosfet.😡

A bad solder joint on one of the feedback resistors R5 or R6 (assuming R7 & R8 not used) can cause 20v at output.
 
#415
If you are using the peter daniels boards make sure you have placed the legs of the output resistors in the right place. Also, the 0.47R resistors in parallel with the pots can blow too - you should check them too. Lastly, make sure the pots are turned all the way to 0R for initial power up. It will take a few turns before you see any action across R11 and R12.

Oh yeah, a few pics of the board will help.

Fran
 
#418
Peter, I want boards for a single transformer stereo amp. One stereo set of F-5 boards ( $15 ) and a power supply board and retifier boards as required, ( $20 ),
Total 35.00 correct? I'll Paypal now, let me know if prices have changed or I'm not thinking right!

RussellC
 
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