Bipolar power supply circuit - OK?

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gusts

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Hello all!

I found a bipolar power supply circuit and used it for a while successfully. I got +15 (V) and -15 (V). But now I get +15 (V) and -22 (V). Input voltage sof the voltage regulators are +35 (V) and -35 (V). In addition, when measuring the voltage at the point indicated by the arrow I get 75 VAC (!!!). Is this normal for such a circuit? I suppose it is not normal. The input voltage of a regulator should be without any AC component.

Thanks and best regards
gusts
 

The schematic is fine although I can't see how you can get 75V AC at that point unless you are measuring against somewhere other than the 0V line.

As those are quite small regulators it is quite likely you have damaged the 79L15 by overloading it. However, in view of the strange 75V you measured it would first be a good idea to know how you took the voltage measurements.

Brian.
 

Thank You Brian for the reply! The most strange is the fact that after removing everything to the right from 2200 uF capacitors these 75 VAC still apear!!
 

The 25VAC wall-wart has a voltage much too high. Its voltage is probably higher when the load current is low. Texas Instruments recommends a maximum input voltage of 30VDC to their uA78L15 and uA79L15 regulators. A 15VAC wall-wart will allow the regulators to operate cooler and last longer.
 

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