Strange RCD tripping - Page 1
Forum section: electronics / general

author: taoybb
author_rank: Contributor
timestamp: April 27, 2020, 04:46:54 am
content: Hello, I 'm having weird RCD keep tripping and still can't figure it out what really happened. I sorted it out and it all came from my PC and audio stuff.At first time, no DAC and Headphone Amp (will be call H.Amp for short) in system nothing wrong, RCD not tripping at all. But after I added DAC and Headphone amp, RCD starting to act weird. I have test some scenario.1st - Plug everything in, DAC/H.AMP always turn off. If I hit turn on button on my PC (Front button that connected to the motherboard). RCD will trip immediately.2nd - Plug everything in, DAC/H.AMP always turn off. If I switch my power strip off, turn on PC with UPS Backup power then switch power back on to provide AC power as usual, RCD will not trip.At this stage, I though that my PC PSU might start to go bad but it's actually not (?) when I investigate further more.3rd - Plug everything in, Turn on DAC but H.AMP still turn off while PC already running, RCD will not trip. (DAC seem to be fine?)4th - From '3rd' step, as soon as I turn H.Amp on, RCD will trip immediately.Then, well it might cause by my Headphone amp?5th - Take H.Amp out from system, disconnect RCA cable and plug it in then turn H.Amp on separately, (PC still running), RCD will not trip. (What? amp still fine?)6th - Plug everything back in (AC,USB,RCA), change AC cord on both DAC and H.Amp with 'No ground cord'. And RCD still trip as soon as I turn H.Amp on.7th - Unplug USB cable from DAC, so no grounding for both DAC and H.Amp, and turn both on.. RCD will not trip.8th - From step '7th', when I plug USB cable in, RCD will trip immediately.9th - Remove DAC and H.amp, RCD will never trip again.I think it could be either DAC or Headphone amp goes bad, so I open both to check inside and it seem to be fine. Both DAC and Headphone amp is transformer based, no SMPS, no filter capacitor on AC side at all, only snubber cap on power switch. I used DMM on continuity mode to check on AC side ,ground or even low voltage (secondary) and it show no continuity at all.My DAC is Fostex HP-A8My Headphone amp is Gustard H10Now I have no clue or idea what really happening. Did anyone got any advise? Thanks you.

author: fourtytwo42
author_rank: Super Contributor
timestamp: April 27, 2020, 06:31:27 pm
content: I don't know anything about electrics in Thailand so a few pictures would be helpful.RCD's trip because there is an imbalance about earth, some cases can beFaulty RCD or to sensitive for application, what is the trip current of yours ?Faulty Y capacitors in equipmentNormal Y capacitors in equipment, just so many of them the total tolerance is enough to cause an imbalanceSome sort of very strange grounding scenario, but I don't even know if your wall outlets have a ground connection ?I don't know if in your long list of trials you included removing the "filter strip" but that may be the problem (to many / to high a value of Y capacitors)Another completely different possibility is that your RCD includes a magnetic overload trip and the inrush current of some devices is sufficient to trip it ?

author: uer166
author_rank: Super Contributor
timestamp: April 29, 2020, 05:59:49 am
content: Have you checked that there is no actual real residual current fault?

author: Electro Detective
author_rank: Super Contributor
timestamp: April 29, 2020, 07:22:21 am
content: Test each device separately for earth leakage and take notes so you can add up the total laterSome sensitive or tired 30mA rated RCDs will trip at anywhere anytime from as low as 17mA to 28mAa good 30mA one will reliably trip from 25mA to 28mAso if all your equipment leakage combined is 12mA or more, you can expect intermittent trip drama with a sensitive or 'time to replace' RCDor you've got a ground loop somewhere or live wire to chassis problem = divide and conquer

author: taoybb
author_rank: Contributor
timestamp: May 02, 2020, 04:26:22 am
content: Hello, sorry for long gone. I have get a electrician and he can't find out what happen but we end up suspect my headphone amp might have small amount of leakage current. So finally I send my headphone amp to get a properly check in a electrical lab and result is it got some current leak between 'Primary' and 'Secondary' on one of it transformer (I has 2 transformer) and it flow from live wire to circuit ground then on chassis and end at earth wire. So I think changing new transformer should fix this (?).Quote from: fourtytwo42 on April 27, 2020, 06:31:27 pmWe got 30mA RCD as standard here, been checking everything as everyone said and end up as above. I think the reason it tripped only when PC turning on is maybe my PC create some spike and it sum up with Headphone amp leakage to be high enough to trip RCD.Quote from: uer166 on April 29, 2020, 05:59:49 amChecked, ans it came from my headphone amp. So need to fix it before I can use it again.Quote from: Electro Detective on April 29, 2020, 07:22:21 amThanks for advice, so I got virtually live wire to chassis as mention above. I did get electrician to test and everything is fine, phew.. no big bill or need to fix something wrong since my electrical system in house is just only few month old. Only need to fix my headphone amp, I already ordered new parts and will change and see the result soon.

author: fourtytwo42
author_rank: Super Contributor
timestamp: May 02, 2020, 09:15:32 am
content: Quote from: taoybb on May 02, 2020, 04:26:22 amTo think that some transformer manufacturer out there is making mains transformers of such poor quality and obviously ignoring safety standards beggars beliefYou are very lucky you have an RCD and it didn't kill you, I would certainly have words with the headphone amplifier supplier and encourage them to change there transformer supplier, if it was DIY did you buy the transformer from Ali-Express etc and are you buying a new one from the same source ?