Simple power supply hack

[hacklordsniper]

Sometime ago i got these two power supplies (they were so cheap i could not resist)  Voltcraft RNG 1501 and 1502. The 1501 is 15 V -1 A and the 1502 is 15V- 2 A with adjustable current limiting.



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I did not have time to check them out until now and compare them with a similiar Chinese power supply. The power supplies were originally built for German market so they should be better!

Check the heatsinking of Chinese unit compared to this one :



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Also the units are properly grounded while the Chinese one is not. The Chinese one used a ultra thin power cable with a knot as strain relief  . The German units even have heat resistant insulation on the wires. They also put heat shrink tubing on the mains switch and used a proper one (while Chinese one used a crappy switch, certainly life threatening). Altrough if the wire somehow got discconected it could easily contact the low voltage side and give you a shock.



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The transformer in Chinese unit was burned so im powering it trough a wallwart. Im using single voltage and the display and electronics are powered trough a dropper resistor (original transformer has multiple windings for powering them). Compare the transformer removed from Chinese unit



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I noticed the electronics are completly the same, there is even place for the current pot, so i just had to mod it :



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Here is step by step to hack the power supply without current limiting to one that will have it...

Solder 2 missing jumpers:

J4 and J 5



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Solder this bridge together



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Remove R3



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Remove this sticker carefully



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Insert a potentiometer in a prepared hole and solder its wires to PCB where is as X1 - A (above the voltage pot):



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Assemble and enjoy your free current limiting



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[saturation]

Great job and photos, thank you.  How do they regulate and ripple under load?

[hacklordsniper]

Great job and photos, thank you.  How do they regulate and ripple under load?

Uh um to be true i even did not bother to do any measurements except calibrating the display accuracy. I have much better power supplies for serious stuff, but i can do it if there is interest