You toasted your caps. You'll need new ones even at 12Vx2 transformer: I'd recommend at least 20V preferably 25V. Bob Ammerman ----- Original Message ----- From: "Tal Bejerano - AMC" To: Sent: Thursday, May 30, 2002 6:45 PM Subject: Re: [PIC]: Need help with a stupid problem > Olin > > About the caps' I found that I use 16v instead of using 35v. > the transformer is what I have in my junk box, you know those who are packet > in plastic case the deliver about 40mA. I will buy 12vx2 tomorrow and check > again. > about the consumption: I didn't measure it but data say "6mA" it's a LM4558. > other problem I have is "hum" look like main 50hz. I feel handicapped with > out a scope but I try to reduces it in many ways. it's really a bad project > for cause this IC is very sensitive. > > > Regards > > Tal Bejerano > AMC - ISRAEL > > > -----Original Message----- > From: pic microcontroller discussion list > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Olin Lathrop > Sent: Thursday, May 30, 2002 10:38 PM > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: [PIC]: Need help with a stupid problem > > > > Attached file as you can see its a small and simple psu. > > this device produce heat to much, it only supply to a opamp about 10-15mA > . > > the regulators are very hot as well the input capacitors. > > You are trying to make a +- 9V regulated supply. The transformer > secondaries are too high voltage for this, which will cause unnecessary > heating in the linear regulators. The unregulated voltages will be 18 * > sqrt(2) = 25V, possibly higher depending on input line voltage and what load > the 18V is specified at. 25 - 9 = 16 volts drop on each regulator. 16V * > 15mA = 240mW. That should cause noticeable heating in a TO-5 package, but > should still be within tolerance. It should certainly not be "very hot", so > something else is going on. The capacitors shouldn't be dissipating any > power. They are either being heated indirectly by the regulators, or > something is very seriously wrong. > > Are you sure the capacitors are installed the right way? If not they will > draw excessive current, get hot, and explode in a minute or so. I'm serious > about this. Don't put your face near this circuit if there is a chance the > capacitors are installed backwards. They are drawn correctly on the > schematic. > > Are you sure the load only draws 15mA? Is that what it's supposed to draw > or what you've actually measured? > > > ***************************************************************** > Embed Inc, embedded system specialists in Littleton Massachusetts > (978) 742-9014, http://www.embedinc.com > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body