Switching Mode Power Supply - How to adjust cut off?

Thread Starter

Eddiie

Joined Oct 12, 2014
16
Parts arrived, 0.15, 0.13, and a 0.12 ohm 5W resistor.
They are way too big and the leads will not fit in the holes. But I made it work for testing purposes.
The results are in......

With the new 0.15 ohm resistor, it powered even less of a load than before.
Same for the 0.13, and 0.12 resistors. With them installed, the PSU would not power what it would with the 'faulty' power sense resistor.

Ok, so I put the old resistor back in, did not make it all the way through the hole, in essence, I left pin 6, the power sense pin floating.
When applying AC to the unit, nothing happens.

I've re-soldered the resistor, and am pretty sure is making connection to pin 6, but still now the output is 0.

No blown fuses, either. No smoke. No heat. Nuttin! Guessing with pin 6 floating it is not working?

I'll look to reorder a 3W 0.15 ohm, recheck my soldering but don't think this is going to get the output back up to 5 amps.
 

ian field

Joined Oct 27, 2012
6,536
I think it is 3 watt, when you get to 5 watts they put it in a different package don't they?
I screwed up by ordering a R15 resistor, not 0R15 that was my question, R15 is different than 0.15 ohm..
The one I ordered just has R15 3W stamped on it. I'll double check when I get home but am prepared to order one that says 0.15 @ 3W
Not necessarily *different* package - usually just bigger.

But there are some "bigger" resistors that won't handle the current because they're a completely different type of construction.

I'd go with the guess already posted of somewhere between 3 - 5W, higher wattage won't hurt anything as long as it physically fits in the space.
 
Top