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Need help sourcing a power transformer

Gourockian

Nov 1, 2007
13
Joined
Nov 1, 2007
Messages
13
UPDATE:- well, I didn't have great success with my home-built PSU so I ended up taking the easy way out. I ordered 2 ready built PSU's from TRC Electronics for $8.94 each (https://www.trcelectronics.com/ecomm/pdf/eps15.pdf). One provides 10.8 ~ 13.5V at 0 ~ 1.38A and the other, 32.4 ~ 39.6V at 0 ~ 0.46A, well within my requirements.
I had an old HP laptop PSU which was no longer needed and after removing all the components on the top side of the PCB, I mounted the two new units directly onto it. This picture shows the experimental stage, using a temporary connector block for the outputs but this was replaced by soldered and heatshrunk flying leads. The A/C power socket was originally soldered to the PCB but again, these were soldered direct to the flying leads. The white I/P and O/P connectors were cut down from a PC motherboard power connector, which accounts for the mismatched wire colors. 20220328_124407.jpg

When I first tried hooking it up to my Yamaha AVS-10 Voice Expander, the panel lights came on but no sound was produced via MIDI from my keyboard. I knew that the MIDI and audio connections were good as it had worked okay with the Yamaha power supply. The problem was that I had adjusted the output voltages, using the small built-in potentiometer, to 10v and 35V under no load condition but when I took them up to 13.75 and 40V, it worked perfectly. These voltages are slightly higher than the manufacturere's ratings but closer to what the Yamaha PSU produces.

One thing I was slightly concerned about was heat dissipation as the HP PSU does not have any vents but after leaving everything running for about 30 minutes, there was hardly any increase in temperature. It took me a bit longer than anticipated to get to final completion but I'm very happy with the result.

Thanks again to all who offered advice.

Al
 
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