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Isolated power supply

Posted: Sun Feb 04, 2024 2:24 pm
by laurie
I needed a fully isolated supply for my stereo board. The Strymon pedals need isolated power because of the digital hash they inject into the power supply when daisy-chained.
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Stereo-board.jpg
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Tried a few options and ended up with this. It is actually fully isolated, and cheap. About USD$40.

It does get warm. I do not know how long it will last, but for now it is working perfectly.
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CP205.jpg
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Re: Isolated power supply

Posted: Fri May 10, 2024 12:13 pm
by laurie
UPDATE - Caline CP205 power supply

After using a couple of these power supplies for a few months and dismantling one to see what is inside, I can report the following.
  • The 8 outputs are most assuredly isolated. There is no ground connection between them, or back to the power pack.
  • Each output is supplied from an independent winding on a small transformer through 7809 linear regulators.
  • The filter capacitors on the linear regulator are 220uF.
  • No-load input to the 7809 is 15VDC, and fully loaded the input is 14VDC.
  • There are no heatsinks on the 7809 regulators - they are free-standing, inside the case with no air-flow.
Bottom line - at 300mA the 7809 regulator is dissipating 1.5W which is enough to cause a temperature rise that pushes the 7809 into thermal shut-down. With high draw pedals (e.g. my Strymons) I am experiencing random drop-outs due to over-temperature cut-out of the regulators.

Running pedals with much lower current draw (e.g. 20mA for a distortion pedal) these power supplies work perfectly.

They are good power supplies, but just can't run my Strymon pedals. They have been moved to my lower current boards, and I've made the expensive decision to buy a Strymon Ojai supply for my main board full of high current pedals.

The Ojai is fully switched-mode (does not use 7809 linear regulators) so does not have the same heat issues as the Caline CP205.

Re: Isolated power supply

Posted: Fri May 10, 2024 12:20 pm
by laurie
CP205-2.jpg
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