| Electronics > Beginners |
| Noisy SMPS putting 100Hz buzz into mains? |
| (1/3) > >> |
| dazz:
Something tells me this is one of those instances when I should be able to find answers on google, and I've tried to no avail, so please excuse me. Anyway, I got this SMPS to power an audio (guitar) amplifier a while back, grounded the output to minimize noise (see picture) and the amp is reasonably quiet when powered by it, but it seems to be inducing a loud 100Hz buzz into the mains that an AM/FM battery powered radio picks up several meters away in a different room. The buzz is also audible (read loud AF) through the guitar amp when I turn the guitar's volume pot all the way down, which grounds the pickups. For what I could gather, the buzz comes from the full wave rectifier. Any suggestions as to how to troubleshoot it, please? |
| HB9EVI:
Hmm, it looks like there several essential parts missing, like common mode choke, X cap and Y-caps, so no wonder that everything possible ends up on mains |
| SeanB:
Simplest fix is a new SMPS, one with actual input filtering, the right class x capacitors across the mains, the right Class Y capacitors to shunt mains noise to ground and LC filtering on the output side. Otherwise you have to add it to this one, and fitting this into the same size housing will not be possible. |
| Gyro:
It looks like a dodgy PSU to me... Firstly, No evidence of EMC filtering on the mains input, so it could well inject switching noise (rectifier and other) into the mains. Secondly, it seems to have the primary side switching transistor and the secondary side rectifier clipped to the same heatsink (top edge). I can see that there is a ground wire running from the mains socket input to the output (bottom left) but I'd want to examine it more closely to ensure that the heatsink is safely grounded. |
| dazz:
And here I thought the transformer labeled JHT-4096 was the common mode choke. I'm so clueless :-DD Isn't CY1 the Y cap? but anyway, I understand there's no way to fix it, so unless it's unsafe for me or my equipment I'll leave it for other purposes other than the amp. Or maybe one of these mains EMI filters would help? |
| Navigation |
| Message Index |
| Next page |