Re: Feedback SSTC failure!

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <teslalist-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Richard,

On 30 Jul 2003, at 20:27, Tesla list wrote:

 > Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
<Robynsaddiction-at-aol-dot-com>
 >
 > Hey List,
 >
 >         I've spent a total of about 26 hours working on a SSTC board 
centered
 > on Justin and Aron's feedback design. The schematics that I used were from
 > Steve Ward's site. I have the board stuffed, and ready to go. However, not
 > even
 > the LED will fire up. With 12 volts in, I am getting 8 volts out of the 
GL7805
 > (should have 5 volts here), and only 12 volts out of the LM317 (should 
have 15
 > volts). Also, the 317 is getting hot. The square wave coming out of the 555
 > is very messy to say the least. Even adjusting the pot. on the power supply
 > will not give me the right voltages out of the regulators. I haven't
 > bothered to
 > check beyond this (wouldn't doubt it if I ruined all those expensive chips
 > somehow). I'm exhausted from two solid days of work on this project, and 
very
 > very lost. Anyone have any suggestions of where to begin? Thanks, 
Richard Harris

The first clue is the voltage coming from the 5V regulator. Either
it's not working correctly, it's in round the wrong way, or it is one
of the maverick types that needs some minimum load before its output
voltage drops to the correct level.

      The second is the heating in the LM317: it sounds as if it's
pretty heavily loaded assuming it's wired correctly. It is not a bad
idea to check that the supplies are all working correctly before
plugging any other components into the board.

Malcolm