07-04-2012, 07:18 PM
Hi Al, are your caps as close as possible to the 317's leads, if not you may have a power oscillator. These devices burst into oscillation at the drop of a hat. If you have more than about 1uF on the output, wire a diode backwards across the chip. If not the cap tries to discharge into the chip and it dies PDQ. 3 diodes and a fuse across the output is a good crowbar. I used similar circuits in an article for WW many years ago and it worked fine.
Is this the low dropout 317 you are using? If not it may need a higher input voltage to regulate properly.
Switch on surge on the valves should not be a problem as the 317 has internal current limiting.
These are nice devices but are full of traps for the unwary user.
Ed
Is this the low dropout 317 you are using? If not it may need a higher input voltage to regulate properly.
Switch on surge on the valves should not be a problem as the 317 has internal current limiting.
These are nice devices but are full of traps for the unwary user.
Ed
