[sdiy] ROLAND PSA-120S 9VDC switching supply filtering components..

[brianw]

Rather than measure the Roland inductors to pick a value, you could just design a passive filter at the frequency that you desire. You can use SPICE software to confirm the frequency response of a simple filter by plugging in values. It might help to first determine the frequency of the noise that you're trying to eliminate, so you have a target for the filter.

Brian


On Jun 23, 2024, at 11:41 AM wrote:
> L1 is a differential-mode choke and will likely be wound on an iron powder core with quite low permeability. T1 is a common-mode choke and will likely be wound on a high permeability MnZn ferrite core.  They attenuate differential and common-mode noise respectively.
> 
> Only way to know their details would be to count the turns and measure the characteristics on an LCR bridge or impedance analyser.  Then you can make an educated guess at the part numbers of the cores from the inductance, turns, dimensions, etc.
> 
> -Richie.
> 
> On 2024-06-23 18:40, Jean-Pierre Desrochers via Synth-diy wrote:
>> Is there anybody who made some researches on the type of inductors
>> used in the new Roland 9VDC switching supplies ?
>> The actual filtering circuit placed in series with the walwart supply
>> block output is shown here
>> Inductor L1 and the toroid T1 are of unknown values.
>> I can measure them with my meters but they are mounted
>> On solid ferrite cores. So making them more difficult to reproduce..
>> I ask because I already have a bunch of surplus 9vdc at 1A SMPS blocks
>> acquired in the past and would like to use them to supply
>> some of my guitar pedals..
>> Using them with their 'raw' unfiltered 9vdc output makes an annoying
>> background noise in the audio signal path..
>> The 'possible' values of these 2 components, or a similar schematic
>> That would do the same job would be appreciated.
>> Thanks.