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Home made dual rail power supply problems

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joedevola:
This is how it looks all together.



I will have 1R sense resistors on the outputs so that I can use a digital panel meter to monitor/set current.

Credit for the voltage section to Rod Elliot of Elliot Sound Products, please see this link to the project and other great stuff http://sound.westhost.com/project44.htm
Hope this helps!

Cheers,

Chris

jimmc:
Hi Chris,
Glad to see you've got it sorted.

By the way there are some 'typos' on the diagram...
As B1 is drawn TR1 should connect to top and bottom of 'diamond' C1 to RH and C2 to LH.
Both halves of R11 are backwards.
Links are missing from D3A/C3 to IC4adj and from D4A/C4 to IC5adj.

I confess that I don't like the voltage adjustment, I think you'll find it's very non linear.


To answer FenderBender,  tracking between the rails is not the best I've seen, but it doesn't matter for most applications.
(The usual method is to have one supply as a 'master' and a feedback circuit to slave the other rail to it.)

Jim

joedevola:
Thanks Jim,

Your help has been invaluable.  I fixed the typos you mentioned, thanks for that.  I just edited the image above so there is not just a stream of incorrect schematics in the thread.

If you can suggest a better voltage control, please go ahead and make a suggestion.  I have that part of the supply hard wired already, but it would be for the benefit of any future projects or people looking at this thread.

Also, noted last night while testing that while both rails regulate the current, the output of the positive rail was reading +39 volts to common with 1 Amp, but negative rail was showing about -19 volts to common with 1 Amp.  Input to the current regs was +/- 39 volts measured to common.  Common is floating at the moment.

Cheers,

Chris

FenderBender:
So does that schematic still need revision?

jimmc:
Hi Chris,
On the diagram left and right connections of B1 are crossed (cathode end is positive).

The standard way to adjust the voltage is a variable resistor from adj to ground (and a fixed resistor from output to adjust).
This gives linear control but can suffer from spikes as the pot wears and the contact resistance between the wiper and track starts to increase.
Probably the best way is to use a separate voltage reference and Op-Amp as Dave has described in his power supply.

Not too sure where you were measuring the voltages.
By 'Common is floating at the moment' do you mean that you are using a single load between + and -.
If you do then the voltages you measured could be normal if you are into current limiting.
Ideally in current limit the current should be independent of the output voltage so whichever side limits first (by even the smallest amount) will drop its voltage until your load draws the set current.
The other side will not be in current limit and will maintain its output.

Jim

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