+13/-10v from Bi-polar PSU

[DrKoester]

Built Ray Wilson's psu: http://musicfromouterspace.com/analogsynth/WALLWARTSUPPLY/WALLWARTSUPPLY.php to supply +12/0/-12 and I'm getting +13/0/-10 instead.  Any thoughts? The only difference in my build and the build instructions is I don't have the heatsinks of my regulators attached to the PCB with a screw because screws weren't supplied and I didn't have a fit. Is this essential to the build at all?

Cheers,
Tom

[Minion]

well the heatsinks wouldn"t make any differance unless the regulators got really got then they might go out of spec but if you have nothing connected to the PSU then that shouldn"t be a problem ....

Make sure you have all of the parts in the right location and there aren"t any shorts on the PCB ..... It is a very simple curcuit so it should work , if it is put together correctly and there are no mistakes then the only thing I can think of is that maybe the regulators are fakes ... I bought a bunch of Fake Chinese LM7815 and LM7915 regulators and most all of them put out the wrong voltage , anywere from 13v to 17v and some just didn"t regulate at all ....

If you have any other regulators arround you might try them , but if you get the same voltages from the curcuit it would point to there being some other problem ....

Good luck ....

[Ripthorn]

Also remember that most regulators won't provide the exactly the right voltage unless they have some sort of a load.  Try loading the circuit with a box or two and see if they change.

[Minion]

I was going to mention that but I have never seen a regulator gain voltage with a load (as in 10v instead of 12v) It has allways been loose voltage with a load but I could be wrong ....

cheers

[DrKoester]

Thanks for the quick replies.  To be more specific, this is built for the MFOS Sub-commander, which I'm currently trouble-shooting.  I'm also new to electronics (< 1 year) and a bit over my head but nonetheless it is built and partially functioning.  I'm not sure if my problems are related to the power supply or not, that's why I was asking for some input.

well the heatsinks wouldn"t make any differance unless the regulators got really got

The heatsinks haven't gotten hot.  I've had the unit plugged in for as long as an hour as I probed around...

Also remember that most regulators won't provide the exactly the right voltage unless they have some sort of a load.

That's what has me wondering, am I too far over tolerance with +13 and -10?

[DrKoester]

anyone?  are these voltages okay or too far off for this project?

[positron]

anyone?  are these voltages okay or too far off for this project?

Hi, first post

The LM7912 used to regulate the negative portion of the voltage has a tolerance of 4% according to the nation datasheet. -10V is way out of spec. What is the AC voltage output from your wallwart?

[Minion]

If your circuit uses a +/-12v PSU the -10v +13v PSU would work to power the circuit with less headroom and wired things might happen if you start pushing the rails in a high gain curcuit .....

You could use a 1k Trim pot wired as a Voltage divider and put it on the +13v rail and tune the voltage (with curcuit connected) down to 10v so at least it matches the other 10v rail and has some symmetry , but this is not a good solution .....


I suggest that you start over again with some new regulators , you can easilly make one of these on perf board/Vero board in 30 min ....


Good luck

[DrKoester]

Thanks guys.  Wall wart outputs 12VAC.  I'm going to try new regulators and report back.

[DrKoester]

And positron, i'm honored to be getting advice from your first post!  And although I too am rather new here, welcome to the board and thanks!

[DrKoester]

Finally got around to replacing the voltage regulators and I'm getting around +13/-11v.  I'm baffled.