[ARC5] DM-32 SMPS sub

[J Mcvey]

I've had this SMPS I bought from Ebay for quite a while , but was inspired By David's recent ventures to revisit the project. It takes in 12 to 24V and the HV is adjustable from 100 to 250V.
Sometimes I have a low frustration level, so when I first hooked the SMPS to the receiver, it was such a noisey disaster i pulled it off and chucked it aside , thinking that I would design one myself!Well, that didn't happen and being the lazy person that I am, I decided to try some noise abatement on the Chinese SMPS.  ( even the IC has has Chinese characters on it !!!!!).
I tested it with a 7500 ohm 20W load to see what kind of junk was on the DC. There was a scramble of waveforms with an amplitude of about 1 Volt riding on the 240 volts. This was surprising because I would think that the waveform would be repetitive with a constant load, but it wasn't.  This may be because it takes a 12 to 24 input as well, causing to constantly "hunt" the input voltage as well?  
Since the HV ground is isolated on this device I used a 1'" D X 0.6 H high perm core that was part of a 1980's vintage TV AC common mode noise suppression choke to filter the HV and terminated that with a 10uf/450V electrolytic bypassed with .047 uf /400v mylar. Both of these are important to filter out all of the noise components.

I tried other smaller common mode chokes, but they didn't have the inductance that this one had, so they weren't as effective. This one worked pretty well, but that wasn't the end of the process. There was still some radiation from the PCB that was being picked up. The quick solution was to attach a grounding lug to the heatsink and cover the top with tinfoil. 
It works! ( see attached photo of the proto-mess)
The finished project will be in a small aluminum box that will plug onto the dynamotor port.


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