Simple Power Supply Stuff

[Bob Zimmer]

I'm building a simple power supply for the ASM-1 and am wondering about a
couple of things.  First a little background.

The PS uses a transformer from Electronics Goldmine which has three
secondaries: 
28 VCT @ 2A, 18 VCT @ 1A, and 16 VCT @ 2A.  I'm running the 28VCT into a
bridge and into a LM317 and LM337 trimmed to +-15VDC. Yes, it does have the
necessary caps and resistors.  I know that the ASM-1 doesn't need +5V, but I
have the 16VCT winding running into a LM7805 (just using the center tap and
one of the other wires for an actual 8V).  I have small heatsinks (5W or so)
on the three regulators.

I'm using a pair of 10 ohm 10W power resistors in series to load the +15
supply and another pair for the -15V supply to .75A each.  My DMM reads
about .73A so I know this is close.

The questions are:

1.  When running like this, each supply is dropping about 4.3 Volts (1.3V
over the minimum) at .75A.  After a few minutes, the heatsinks seem to get
too hot to touch, but the regulators do not shut down!  How can I tell if
this is too much heat for normal operation?

2.  The power resistors also get very hot and actually put off an odor from
the heat.  Is this normal?

As far as my math allows, everything should be within tolerances for current
and wattage.

  >=== Bob Zimmer -- Philadelphia PA ===<
  >=== bzimmer at voicenet.com          ===<