Bad design? Bad components? Something else?

[madan1]

Hi everyone.
I really don't know from where to start
Nah.. none of the rest is important.. just watch the video and see the photos.. then I will answer your questions ( if any ).

video - https://www.dropbox.com/s/fj4n2dalp5...88093.mp4?dl=0

oh, basically I would like to hear your ideas about fixing it...

p.s. all parts test fine.

[budm]

Re: Bad design? Bad components? Something else?

I cannot access the video.
So why is the fuse bypassed?

[madan1]

Re: Bad design? Bad components? Something else?

Hmm, that's odd ( about the video ).. anyway, here it is rar-ed.
The fuse is bypassed, temporary... at least that is the plan .
Indeed, today I couldn't find such fuses in the local electronics store. I hope I'll have some of those in stock by the time I get the unit(s) back together.
Also, I already blew few ( of those 3A that are inserted in the UK plugs ) while banging my head in the wall trying to figure out what made the bang, but after that tests fine.

p.s. the video is with a current limiter.

[petehall347]

Re: Bad design? Bad components? Something else?

pesky fuses who needs fuses ?

[budm]

Re: Bad design? Bad components? Something else?

So it looks like it has 12VDC SMPS, and Motor (M - and Switched M + through the relay) drive output?

I saw the video, so it has arc over between the Neutral and the dropper resistor R2 for bridge DB1.
The clearance between the resistor and the Neutral leg of the choke looks to be <0.25". I also wonder why the coating on R2 is scraped up.

[madan1]

Re: Bad design? Bad components? Something else?

Yes, the SMPS is for the control board ( turns on the relay on the power board ). The rectified output just powers the motor.

Alright - some background info - these are "michelin tyre inflators". Both came to me dead. One of them had both fuses blown ( the on on the board and the other one in the plug ). The other one had blown only the one on the pcb. One of the units seems to be completely new ( still has the plastic cover on the display ).
Both boards arc and of course - blow fuses.
One sparks between the resistor and the common mode choke, the other one - between the resistor and the rectifier.
So I wonder if this is a really bad design ( components placed too close to each other ) or the resistors are from a defective batch for instance.
If the resistors are faulty, then it is easy - just replace them.. but if the design is bad, just a replacement will not make any good in long term.

And again - all components seem to be fine. When 50vDC is applied on the input, there is almost none consumption and the smps tries to boot.

[budm]

Re: Bad design? Bad components? Something else?

The resistor itself has breakdown Voltage spec (https://cdn.badcaps-static.com/pdfs/...ad10cec911.pdf), but from the way the resistor which is connected to the Hot is sitting real close to the Neutral leg of the CM choke. I would put a dab of electronics grade RTV on the CM legs to give more creepage (https://www.tempoautomation.com/blog...nce-standards/).

[madan1]

Re: Bad design? Bad components? Something else?

So you are thinking that the distance between the components is not enough? Probably designed with 120vac in mind?
By the way, our plugs do not have direction, so N and L are irrelevant.
I removed the resistors on both units and they are faulty. According to the color code, they should be 10ohms, but one measured 8.5mO, the other - few hundreds of k. Installed a new one ( unfortunately 1/4w, so tomorrow will go to the store for the correct ones + fuses ), put it in heat shrinking tube and did some tests. Everything worked fine.

[momaka]

Re: Bad design? Bad components? Something else?

Given the cheap electrolytic caps and overall cheap look on the PSU boards, I think not only is the creepage distance too small, but possibly those 10-Ohm resistors either weren't specced properly for 230V AC or they are simply cheap rubbish themselves.

Probably best to replace those resistors -AND- isolate everything with silicone glue. Of course, also make sure to clean away all of the black charring from the PCB and components, as that stuff is conductive.

pesky fuses who needs fuses ?

Exactly!
And real true men plug everything directly into 3-phase 380V AC.

[budm]

Re: Bad design? Bad components? Something else?

So you are thinking that the distance between the components is not enough? Probably designed with 120vac in mind?
By the way, our plugs do not have direction, so N and L are irrelevant.
I removed the resistors on both units and they are faulty. According to the color code, they should be 10ohms, but one measured 8.5mO, the other - few hundreds of k. Installed a new one ( unfortunately 1/4w, so tomorrow will go to the store for the correct ones + fuses ), put it in heat shrinking tube and did some tests. Everything worked fine.

You still do have Hot and Neutral so you will still have difference potential between the resistor and the CM choke, it does not matter if the plug is polarized or not.

[madan1]

Re: Bad design? Bad components? Something else?

You still do have Hot and Neutral so you will still have difference potential between the resistor and the CM choke, it does not matter if the plug is polarized or not.

There is no question about that. I'm just saying that here, we never know which is live and which neutral .

[ChaosLegionnaire]

Re: Bad design? Bad components? Something else?

not knowing which is live and neutral? that must make electrical work very funn in bulgaria! electrical work must be like a box of chocolates there. u never know which one, live or neutral, u're gonna get or what will give u the zaps and tingles!

[madan1]

Re: Bad design? Bad components? Something else?

not knowing which is live and neutral? that must make electrical work very funn in bulgaria! electrical work must be like a box of chocolates there. u never know which one, live or neutral, u're gonna get or what will give u the zaps and tingles!

Mmm.... do you feel lucky today ?



Also, most home installations do not have a dedicated ground lead... which means that the ground pin is actually connected to neutral. We've had occasions when after changing the electricity meter, the technicians reverse live and neutral... so yeah - like a box of chocolates.

[momaka]

Re: Bad design? Bad components? Something else?

not knowing which is live and neutral? that must make electrical work very funn in bulgaria!

What he meant by not knowing which is Live and which is Neutral is that because of the Schuko plug used in most of EU, you can take that plug, turn it 180 degrees, and plug it again into the socket that way too. So this will essentially reverse Live and Neutral going to the device. (Ground will still be ground, if the device has the connections for it and if the plug is wired to modern codes.) This is the same as 2-prong devices in North America that use a non-polarized non-grounded plug - you can take the plug and insert it any which way you want into the wall outlet.

But aside from that, there are modern electrical codes in Eastern Europe now, same as in rest of the EU - i.e. Live should be brown, Neutral should be light blue, and Ground is green or green with yellow stripe. At least for all modern-built buildings, that's the code they have to conform to. Of course, in E. EU, it all comes down to who you hire to do the work. Because of more lax regulations and inspections, there are a lot of incompetent contractors / workers, and that can indeed lead to situations where you might have someone swap Live and Neutral in the panel. Though most likely, I imagine that happens more often with older buildings (particularly most condos build during Communist times), as these often did not have color-coded wiring nor ground. And then.... yeah, it's a bit like a box of chocolates... or Russian Roulette. (230V AC gives slightly more "ouch" than 120V. )

[ChaosLegionnaire]

Re: Bad design? Bad components? Something else?

230V AC gives slightly more "ouch" than 120V.

lol i think thats nearly double the voltage! so i think its double the ouch and double the funn and tingle! truly an exciting job to have! hehehe!

[zx8401]

Re: Bad design? Bad components? Something else?

I would remove the resistor and clean it, it could be surface muck thats creating a path.
Or make a replacement part with three resistors in series, less voltage across each resistor and arranging them in a " n " shape will keep them away from the pcb.