reducing output

[Lostcause]

Hi chaps, I have variable output SMPS that has 6 steps from 5VDC up to 15VDC and I wondered if it was possible to lower the output of one of these steps by half a volt or so?
One setting is supposed to give 13.5V but it's nearer 13.9V which is too high. The next one down is 12V but ideally I'm looking for 13>13.2V.
I can post pictures if needed.
Any input is, as always, appreciated.

Thanks
Lee

[BWRX]

Put a diode in series with the output. That should drop about half a volt.

Or you could tweak the resistor feedback values (assuming that's how the different voltages are obtained) to give you slightly lower output.

I'd imagine this will be used as a supply for a Tripath based amp, eh?

[Lostcause]

Originally posted by BWRX
Put a diode in series with the output. That should drop about half a volt.

Or you could tweak the resistor feedback values (assuming that's how the different voltages are obtained) to give you slightly lower output.

I'd imagine this will be used as a supply for a Tripath based amp, eh?

Right on the nose there Brian!

I don't want to go back to 12V now that I've sampled 13.2
But I would like to put this little SMPS in my latest amp and see how it sounds against my old linear supply.

I wondered about the feedback resistors, it looks like 3 of the settings are all linked to the same trace with different values so I think I'll have a play with that idea.

Then maybe I'll get some of your new modules if there is another run

Ta very much
Lee

[Lostcause]

Ok so using standard resistor values I'm now at 12.8V, that will do nicely, thanks Brian

[BWRX]

If you want to fine tune it some more you can put a large pot in parallel with one of the feedback resistors that makes the output voltage higher than 13.2V and slowly increase it's value until you get the desired output voltage. Then remove the pot and measure it's resistance. Knowing the value of the other feedback resistor and the resistance of the pot, calculate what value resistor you should be using to get 13.2V.