What does it do with a load (like even a 4.7K R) attached? (I think Q1 or Q2 may be 'leaky' though - impurities have a way of 'migrating' within devices with the passage of time and elevated temperatures don't help either ...) RF Jim ----- Original Message ----- From: "Dale Botkin" To: Sent: Monday, November 04, 2002 10:26 PM Subject: [EE]: Power supply rework (again) > > OK, I did some desoldering and hacking tonight to test one possible > configuration and see how it would work. I removed the old regulator > circuit and replaced it with my own. See attached schematic - an LM317T > driving the bases of the two 2N5885 power transistors. I omitted a couple > of 2200uF caps on the input side of the regulator, two more on the > collectors of Q1 & Q2. > > When I unplug J3, disconnecting the regulator from the transistors, I get > a nice solid stable 28.5V from the LM317, and I can adjust it up or down. > As soon as I connect the regulator output to the transistor bases, I > measure 44.0V on the output of the LM317 and at the transistor bases. No > adjustment regardless of the pot setting. The collectors of Q1 & Q2 are > at 44.7V. This happens with or without a load on the emitters of Q1 & Q2 > - I used a 100 Ohm resistor for a test load. No appreciable difference > with or without it. The LM317 stays cool the whole time. > > I don't measure any obvious collector-base shorts on Q1 or Q2, but it sure > is acting like it. Or am I missing something? > > Dale > --- > We are Dyslexia of Borg. > Fusistance is retile. > Your ass will be laminated. > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics