3x powersupply for rpi

[TommyBoy]

my notes about how to connect power supplies
the ic is removed using two soldering irons, then it was easy,

[ritsjie1971]

Very nice TommyBoy!

Actually I'm working on my linear psu too now. I'm gonna use the LT1963. I have to order the parts and then build it together.

[TommyBoy]

you are welcome.
please use as SHORT wires as possible, make room for large local caps like my picture show,
DOUBLE check your PI hardware before removing the original switcmode chip,
like measure the 1.8 and 3.3 and 5.0 volts at the locations i have shown.
different PI pcb versions exist, and they have moved the caps and caps numbers a little bit.
also very important to double check the voltages you make with the new regulators,
trim the two low voltages in as accurate as you can +/- 50mV and the 5V a bit to the high side,
like 5.05mV or 5.10V since your USB disk love a little bit to the high side for biggest margin to fail.

Another trick for noise hunters, see the cap near the USB connector, side of board, near IO pinrows ?
it is called C97 on my PI
it is mounted directly on USB power, after the 5V switch and measure system,
add a 1000-2200uF / 16V switch mode super duper grade cap accross this one,
now peak currents from usb disks cant enter your pi.

please share pictures, and results..

[ritsjie1971]

20170218_213347.jpg (145.58 KiB) Viewed 1819 times

My spare time is quite limited these days, as a lot of it goes to my photography hobby

Anyway, I started with the power supply. The main linear supply is finished. With this, I'm gonna feed the stablizers for the 5V, 3V3 and 1V8.

I used a 6V transformer, 4 3A schottky diodes as rectifier, and 4 1500 μF in parallel for smoothing.

[ritsjie1971]

Rectifier and smoothing elco's.

[ritsjie1971]

Schematic, so far. No rocket science at all. Power On LED is not drawn here, but it's connected at the output right via a 470 Ohm resistor.

[pelliott321]

Just one question
What is the resistor across the smoothing caps for? What is the value?

[ritsjie1971]

[TommyBoy]

what is your LOADED voltage at v-min measured with a scope ?
to be able to generate 5.00 stable, with no ripple the min pulse must be over 6V
so your trafo deliver too Low voltage,
use a 9V AC trafo and shotkey diodes will give correct range, then add a pre-regulator adjusted to 6V
this way your transfer a perfect DC supply into your critical unit, and this way it can make perfect 5V and all the other voltages,

[JohnC]

I went down the external DAC route with clean power supply (DIY) with good results. This way, so long it's USB DAC Audio Class 2 compliant, I can have better control of what chip to be used and this method works with Rune very well:

A) The following post has a very simple method to separate the power supply using a Y-split USB cable. It works like a charm:


Go to Post #1326 for the illustration. It works great with iFi iDSD Micro for DSD or DXD files.

B) Another option is to use a DAC that separates the power for you. I personally find the HiFiMeDIY Sabre USB DAC 2 (External PSU) sounds good and have good value for general uses.

C) Lastly, the linear power supply mod for HiFiBerry DAC+ Pro is pretty straight forward.

John