Hi Folks: I'm working on an A8000 that seems to have a flaky power suppy. After changing the electrolytic caps, the stink is gone but after sitting, it still blows fuses. On 12V input, it still blows the 7.5A fuse. If I change it, turn it back on, it works. I've ran it all night like this, with no overheating. Let it sit overnight, off, just plug it in in the morning, and it tries to come on, blows the fuse. I have a limited 12V supply on it now to see what's happening before it blows the fuse. It seems to be making 5 and 12V +-, but the snubber looks like it's getting too hot. The resistor is black now.. The snubber-cap looks good. Maybe this diode is shorting? Maybe this thing shouldn't be ran without the internal battery connected (it's dead)? Why would this be coming on by just plugging it in? Sometimes when I press the 'battery' side of the switch, the supply puts DC voltage on the gates of the FETs and that's pulling my limited supply down. The FET's then go linear and quickly get hot! Why would it try to run at low voltage? I see no switcher-chips, just op-amps. A clue maybe, there is some substance under one of the caps I changed. Maybe electrolyte? Freon TF doesn't seem to take it off. I don't know... I have 2 1200'service monitors that have had no problems. Thanks for any leads Harry
- posted
16 years ago