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PSU Current Limit Problem
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author PSU Current Limit Problem
When I measure the current limit across the +15v and 0V terminals, I am only getting 530ma, and as well as the +ve LED going out, the -ve LED is going very dim. Taking the probes off, the LEDs come straight back on. Measuring across -15v and 0v I get 740ma, and just the -ve LED goes out. I'm using 1R current limit resistors and a Yamaha PA-20. Both the positive and negative voltages are at 15v.

Any suggestions of where I might have gone wrong would be most appreciated, as I'm quite keen to build something that makes a sound now!
530mA does seem a little low. It could be that the 1R resistor has a slightly higher resistance than expected. Perhaps as much as 10% out.

But these are fractions of an ohm so maybe just simply putting a bit of fresh solder around the 1R resistors pads will be enough. It's a big pad and the resistor itself is pretty big so it will readily steal away some of the heat from the soldering iron thus making it harder to make a good joint.

Also I've had a few of these newer RoHS (ie. Pb free) power resistor's leads not solder well. I think they tarnish more easily than the older one with Pb/Sn tinned leads. This means they need that little more time to solder.

The -ve LED should dim when you short out the +ve rail so that bit is OK.

Thanks for the quick reply - I'll investigate those ideas.
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