FALKEN said:
thanks!! I got a box for it. in your ps schematic there is a 120v 1A fuse. all i could find is 250V 1A. is that ok or am I screwed? also, is it ok to omit the switch, or put it on the +/- 15V side ?
The current rating is what truly matters. for 120V use a 125V 1A and a 250V 1A fuse serves the same purpose.
Generally power switches are put between the primary transformer coils and the mains, so when you open the switch the power transformer drops its magnetic field and as the capacitors on the secondary side drain from the load, the entire power supply becomes unpowered.
*I* prefer to use a DPDT switch and cut both the hot and neutral lines, so the transformer isn't attached to either leg of the outlet - just in case it's plugged in when I take the cover off and poke around. Even though plugs and outlets are keyed, once in a while you may have the misfortune of plugging it into an outlet that's miswired, so when the SPST switch breaks the hot lead, the white lead, i.e. neutral, might actually be hot. Hit that and the metal case with a screwdriver...
The last +/-15V power supply I made also had a 120V coiled DPDT relay in parallel with the primary transformer coil. When the power switch was on, the relay would energize too, and using the normally closed contacts, disconnect a 32V 1A light bulb that was inside the case. When I powered off the power supply, the relay immediately de-energized, switching the light bulb onto the secondary windings, draining the filter capacitors almost instantly. This is a monkey way, i.e. cheap way, to make the secondary side of the power supply "die" faster, if the load is smaller than the filtering capability of the output capacitors (which is what you want with audio circuits). This way, the "thump" upon power down is significantly reduced.
Power up thump is a whole 'nother story.