Power inverter blows fuse when 12V is connected.

Reply

  #1  
Old 02-13-16, 10:43 PM
Member
Thread Starter
Join Date: Feb 2016
Posts: 8
Received 0 Votes on 0 Posts
Power inverter blows fuse when 12V is connected.

Hello everybody, thank you for the help..
I have a 500W inverter (made in china of course), it cost me too much money, i'm not having a good economic situation.. so i can afford to buy another one.. the inverter has 2 months... it worked fine until yesterday, i connected a 500W powerdrill and used for about 15 minutes.. everything was fine.. so i ended with the powerdrill and disconnect everything with no troubles.. today the inverter is not working.. the 40A fuse is blown.. so i replaced it.. but when i connect the 12V wires to the input the fuse blows again.. i tried 3 times.. the connection is directly to a 12V battery... the inverter has nothing connected to the AC output.. I have been reading the entire day about how to solve this.. all the people is talking about replacing the mosfet.. however i didn't find anyone with the same problem.. Could this short circuit be related to the mosfet?...
if anyone with the knowledge can reply i will really appreciated it..

thanks in advance.
 
Sponsored Links
  #2  
Old 02-13-16, 11:18 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 54,665
Received 519 Votes on 489 Posts
Welcome to the forums.

As a low voltage specialist I can tell you that most 12vdc electronic equipment has a reverse polarity diode connected to the 12v incoming leads. That diode conducts when the power is connected backwards and causes the fuse to blow. So..... most likely you connected it momentarily backwards and that diode is now shorted.

If you take the cover off and post a few pics we can probably get you going. We need to see the area of the board where the power wiring connects. http://www.doityourself.com/forum/el...-pictures.html
 
  #3  
Old 02-14-16, 07:35 AM
Member
Thread Starter
Join Date: Feb 2016
Posts: 8
Received 0 Votes on 0 Posts
Hello PJmax, i really appreciate your fast and extensive reply.. however, i must say i did not FOR SURE connected the wires badly or inverted, not because i don't make mistakes but the thing is the 12V is always connected to the same battery... because i have is a power switch between the battery and the inverter, so when I finish using the inverter i just turn off the switch.. what i mean is that the invterter was always connected, nobody touched anything and stops working.. Do you think still can be this diode? (a zener i suppose).. thank you for the help and for the warm welcome... people in forum always amaze me. are like greenpeace guys. helping with no reason.. thank a lot.!
 
  #4  
Old 02-14-16, 09:44 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 54,665
Received 519 Votes on 489 Posts
The diode that is across the input wiring is just a general purpose HD diode. When the leads are connected backwards the diode is supposed to conduct and blow the fuse. In theory all you should have to do is to replace the fuse. However, 40A connected in reverse to a diode will cause it to dead short and stay that way.

I'm not doubting your word but I can't tell you how many people brought items in for service that supposedly weren't connected backwards. It was easy for me to tell because that reverse polarity diode was dead shorted and it could ONLY short if connected backwards.

If you want help servicing that unit.... post me some pics.... I'll tell you what to check.
 
  #5  
Old 02-14-16, 11:22 AM
Member
Thread Starter
Join Date: Feb 2016
Posts: 8
Received 0 Votes on 0 Posts
again Pjmax, thank you a lot!!..

here are some pictures.. since i don't understand much about componentes a made a few marks with references so i can understand what component do you mean...

A) there is a wire.. i didn't cut it.. and i didn't find the rest of the wire.. it is just a cut wire that measure about half inch.. is this normal?.

B) those are the famous mosfet.. is there a way to find if there is any of these burned out?.. i can't connect 12V.. maybe i can plug 1V and test with the multimeter?.. just guessing here.

C) I think this is the diode you are talking.. am i right?.. not sure it looks like something that i would call DIODE..

D) is where the 40A fuse is located. it is a regular fuse like a CAR fuse....


at simple sight anything looks burned.. the same if i flip the board, everything seem to be normal...

any ideas?

thanks!!!
 
Attached Images    
  #6  
Old 02-14-16, 01:29 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 54,665
Received 519 Votes on 489 Posts
The diode(s) are shown as E in your picture. The protection diode would look like that. There are 4 there in this picture. Are there any other large ones like that elsewhere on the board ?

Do you have the ability to take BIG pictures..... like 2-3megs 3000x3000 ?
I need a mega picture of the front and back. They can't be posted here. The board won't allow big pictures. You'd need to put them on a free hosting site or send them to me and I'll host them.

Name:  inversor1.jpg
Views: 1040
Size:  37.7 KB
 
  #7  
Old 02-14-16, 01:31 PM
Member
Thread Starter
Join Date: Feb 2016
Posts: 8
Received 0 Votes on 0 Posts
INDEED PjMax.. i'll upload the shots in 5 minutes

THANK YOU!!
 
  #8  
Old 02-14-16, 01:44 PM
Member
Thread Starter
Join Date: Feb 2016
Posts: 8
Received 0 Votes on 0 Posts
well..let me know if these shots will do the job
there are no other similar diodes beside these 4 diodes.

www.4render.com/tmp/diode01.jpg
www.4render.com/tmp/diode02.jpg
www.4render.com/tmp/diode03.jpg
www.4render.com/tmp/diode04.jpg
 
  #9  
Old 02-14-16, 02:08 PM
Member
Thread Starter
Join Date: Feb 2016
Posts: 8
Received 0 Votes on 0 Posts
sorry i think i missunderstood you.
here is what you want

www.4render.com/tmp/top.jpg

i don't see anything like that but bigger..
 
  #10  
Old 02-17-16, 09:58 AM
Member
Thread Starter
Join Date: Feb 2016
Posts: 8
Received 0 Votes on 0 Posts
please.. can anyone tell me what should I look at?
 
  #11  
Old 02-17-16, 12:24 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 54,665
Received 519 Votes on 489 Posts
Hiya buddy. Your picture links are not working. I sent you a private message.
 
  #12  
Old 02-17-16, 01:29 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 54,665
Received 519 Votes on 489 Posts
The pictures are good. It looks like those four diodes are in parallel and are used for protection.
Do you have an ohmmeter ? Set it to Rx1 and check across those diodes.

You'll probably need to unsolder them from the board to check each one singly. I'd imagine all four may be shorted.
 
  #13  
Old 02-17-16, 01:43 PM
Member
Thread Starter
Join Date: Feb 2016
Posts: 8
Received 0 Votes on 0 Posts
thanks PJmax! understood!.. one question.. since i'm not too experienced can i use a low voltaje battery?. like 4volt.. or 1.2.. or something that will avoid the short circuit and burn and test the diodes without unsolding?.. just guessing with this theory..

also, how should i test these?.. i mean.. this is what i'm supposing your are saying:

Battery 12V to one pole of the diode, the output of the diode to one pole of the ohmeter and the other ohmeter to the negative of the battery... am i right?
 
  #14  
Old 02-17-16, 01:45 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 54,665
Received 519 Votes on 489 Posts
At this point we just want to see if any of the diodes are dead shorted. Just use the meter probes directly to the diodes.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: