230v Introduced to a 115v to a Space Heater (Circuit Board) Correction - Fuse WAS Blown

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wozDaddy

Joined Feb 26, 2015
25
I have what appears to be a simple pc control board. 230v was accidentally introduced to it. Fuse was not blown, but no indication of power now when connected to 110-115 ac. Nothing looks burned. Do not know if repairable. A picture is attached. (I have replaced obviously damaged components on misc. boards in the past with success)
Can you help ?
Thank you
 

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MaxHeadRoom

Joined Jul 18, 2013
28,699
Find out how the 115v is translated down to the DC required, SMPS, Transformer etc, and check the power supply first.
From the pic, there does not seem to be any AC to DC power conditioning components.
Max.
 

MisterBill2

Joined Jan 23, 2018
18,587
That is a very small and inadequate resolution picture, and so it is not possible to see other than a lack of serious big damage. Are any of the copper tarces on the back damaged? That black item towards the center may have some damage but it is impossible to see with this picture.
 

Tonyr1084

Joined Sep 24, 2015
7,905
Are any of the copper tarces on the back damaged?
I would expect the fuse to blow before traces could burn. With the board in hand I think @wozDaddy would have noticed a significant burn like that. Not saying it couldn't happen, I've seen stranger things.

Last year I repaired a space heater for a neighbor. It was one of those oil filled radiator type heaters. The only problem on that heater was the fusible link.

My recommendation to Mr. Daddy is to check for continuity from the plug (not plugged in of course) to the PCB. If there's an open line then I'd suspect the fusible link. If you don't know what they look like - just google fusible link and I'm sure images of a leaded device with a glass seal on one end will pop up. Just understand that you can not solder those in. The heat - well, heat is one of the two things that will cause it to blow. The other is excessive current. It's possible it blew before your fuse had a chance to.

Another thing I'd look for on the board is the capacitors. If you have a capacitor that is rated for 200 volts and it's been exposed to 230 volts I think that might be one point of failure. However, usually when a capacitor fails it does so spectacularly. I encountered an issue where, as a noob myself, where I put a 16 volt electrolytic capacitor across 120 VAC mains. It virtually vanished and my dad came into my room asking me what went bang. Of course, I can only guess at what may be wrong, but these are the things that come to my mind. If none of the above then it's possible you blew out the microchip.
 

MisterBill2

Joined Jan 23, 2018
18,587
I once made it easy to accidentally apply 240 volts to 120 volt devices. No matter how many warning signs are placed on an outlet the unthinking folks will never read them. All it takes is a double outlet box and an extension cord tied to the hot side of two circuits on opposite phases. The unthinking will disconnect the cord from the 240 volt device being tested and connect it to a 120 volt vacuum cleaner without ever thinking.
 

spinnaker

Joined Oct 29, 2009
7,830
I once made it easy to accidentally apply 240 volts to 120 volt devices. No matter how many warning signs are placed on an outlet the unthinking folks will never read them. All it takes is a double outlet box and an extension cord tied to the hot side of two circuits on opposite phases. The unthinking will disconnect the cord from the 240 volt device being tested and connect it to a 120 volt vacuum cleaner without ever thinking.
That only happens if you doubled down on the stupidity and either wired a 120 outlet to a 240V service or you wired some sort of bastardized extension cord to the 240 outlet. Signs or no signs no one to blame but the installer.

I have several 240V outlets in the garage. Each one is clearly labeled. On top of that it has a standard 240V outlet. It is impossible to connect a 120V device without a whole lot of effort.
 
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Wolframore

Joined Jan 21, 2019
2,610
yeah definitely stupid :D

I really can't see much from your picture. Please include a better picture

1. what is the board for?
2. what is it doing?

It looks like some sort of controller chip on this and my inclination would be the regulator is shot due to the over voltage... but that's only a guess and can't see much in the picture and guessing in the dark.

power supply is on lower left... I think that white blob is a transformer and there are diodes (maybe half bridge to left of that.) And possibly a 7805 regulator surrounded by filter caps. above that.
 
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Tonyr1084

Joined Sep 24, 2015
7,905
It is impossible to connect a 120V device without a whole lot of effort.
Guaranteed: When you make something idiot proof someone comes along and invents a better idiot!

OK, enough of the name calling. At some point in our careers - hobbies - endeavors we've all done something that constitutes the label "Stupid" (as in a stupid act - NOT as in a person is stupid). In high school electronics class I built a switch box with outlets. One outlet wasn't working so I started checking continuity and checking for shorts. I FORGOT TO UNPLUG IT! With the meter on ohms I struck hot and neutral. There was an instant flash of light within the meter and the needle was thoroughly bent from slamming from zero to 100% in under a microsecond. WE ALL MAKE MISTAKES!

I'm sticking with my suspicion that the fusible link is the next thing to check. Checking continuity of the power cord (DEFINITELY NOT PLUGGED IN) (I say that because, as mentioned above - I've done that) (and you can call me stupid if you like - I'm not easily offended). If there is full continuity from the plug end all the way to where the power reaches the board then you know the problem is likely in the board. Given the lack of apparent damage, chances are this board may be destined for the recycle bin. At that point I wouldn't even look for parts from it to scavenge for other projects. But first things first - do you have continuity from the plug to the board? Both wires? All three if grounded?

Diagnostics requires elimination of parts that are still functional. Isolate all functional parts from the one (or possibly multiple) non-functional part(s) is the way to fully diagnose the problem BEFORE you start repairing.
 

JohnInTX

Joined Jun 26, 2012
4,787
Guaranteed: When you make something idiot proof someone comes along and invents a better idiot!
OK, enough of the name calling. At some point in our careers - hobbies - endeavors we've all done something that constitutes the label "Stupid" (as in a stupid act - NOT as in a person is stupid).
Indeed. It is not helpful nor acceptable here to go off on a new member for making mistakes. Remember all of the 'stupid' things you did over your careers and show a little understanding. I personally could write a book on all of the mistakes I made over an otherwise successful career - some of them legendary like mis-connecting a Jones plug and applying line voltage to the TTL supplies of our one and only prototype right in front of the CEO and potential investors. That was a long night. All of our benches had a styrofoam block where we would stick the parts we'd blown, bending the leads to make them look animated. We all had quite the parade of failure there for all to see. I personally was the creator of the 'Burnt Transformer Award' where smoking something important would get you the honor of wearing a little smoked transformer on a zip-cord loop around your neck for the rest of the day. My creation of that award was entirely unintentional. When wiring the machine shop, I grabbed the wrong phase of the power and put 277V on the 120V outlets I'd just wired. Our poor little PA system and its power transformer was the unfortunate victim of my inattention.

We all have stories like that so... let's give the TS a break, shall we?
 

Tonyr1084

Joined Sep 24, 2015
7,905
@wozDaddy Lots of great photographs. However there's little we can tell from the pictures. Troubleshooting comes down to you yourself. Do you have a digital multi-meter? If not - they're available at every hardware store I've ever visited, in their electrical department. You don't need a clamp meter (for measuring amperage). I have one for just such purposes, however rarely use it for more than voltage checks and ohm checks. Using the ohm setting and touching one blade of the power cord, check the wire all the way to the board. If you get zero ohms (often a meter won't read complete zero, but as long as its less than an ohm you can call it good. Do the same with each wire from the plug. Then report back with your findings please.
 

Wolframore

Joined Jan 21, 2019
2,610
OK thanks for the awesome pictures, that helps...

Looking up the part number it is a Control board for EdenPURE/SunTwin infrared heaters. The board is discontinued. There is a new board that replaces this but connectors look different.

The one part that's not shown is the transformer, it is off view connected with the white wires. It is rated for 120VAC = 13.5VAC 200mA.

I would suggest starting with IC1 and IC2.
Check the diodes D1-4
Also check continuity on that fuse, sometimes they can blow and look normal.
Check the transformer. If that's burnt you can get a replacement.
transformer or you can find any rated for same and change plug ends.

IC3 looks like a PIC or AVR or some type... if the high voltage got past IC1 and IC2 the board is toast.
 

MisterBill2

Joined Jan 23, 2018
18,587
Actually, after examining the pictures, the very first question is about the fuse. Is it OK? Check with a meter. That would be way to simple a fix, but one may be lucky. Next I would suspect that light blue device next to the red wire, it may be a varistor, and they sometimes go shorted, with almost full conduction. That will take out as many fuses as you put in. After that, try applying isolated line voltage through a light bulb to limit current. A small isolation transformer should be adequate if you do not run the heater elements.
I see two sets of 4 diodes that may be rectifier bridges, are those working?Is there voltage across the big capacitors? Since nothing looks burned or exploded, probably some part near the power in point of the circuit has failed open. So systematic checking, moving down stream from the mains feed, is the way to go. A circuit diagram would be handy but it can be fixed without that luxury if needed,
 
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