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Anonymous Poster #1

Please reply fast , its an emergency.

12/14/2012 2:15 PM

Hello buddy,

I had connected two SMPS in series then resistor inside the SMPS burned out. What would be reason for that?
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Doorman
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#1

Re: Please reply fast , its an emergency.

12/14/2012 2:17 PM

Overload.

Was this one of the startup resistors?

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redfred
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#2

Re: Please reply fast , its an emergency.

12/14/2012 2:32 PM

I'm going to take a wild guess here and say that something more than just one resistor died. I'll also guess that you have no idea how to tell.

Good Luck

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Yahlasit
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#3

Re: Please reply fast , its an emergency.

12/14/2012 2:40 PM

Maybe the negative pole of your power supplies are not floating from the chassis ?. If thats the case, you've made a short circuit to the one which negative lead was going to be your ground.

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lyn
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#4

Re: Please reply fast , its an emergency.

12/14/2012 2:55 PM

Two in series. Which one blew?

If it's really an emergency, buy two more power supplies.

This forum doesn't make house calls and we can't trouble shoot very well over the internet either.

Resistor Failure Modes & Reliability Analysis

I'm with redfred on this one.
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Yahlasit
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#5

Re: Please reply fast , its an emergency.

12/14/2012 3:38 PM

Buy or build two linear power supplies, they are electrically isolated from the mains line (only magnetically coupled), or build one bi-polar linear power supply.

What are you doing? how did you connect them in series? was there any load? please submit a drawing.

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#6

Re: Please reply fast , its an emergency.

12/14/2012 4:13 PM

Why would you connect them in series anyway? Were you trying to get 48VDC from 2 24VDC sources? If so, did you put reverse bias diodes accross each one? If not, one can come up to voltage faster than the other one and apply a reverse polarity voltage through the load to the other one, which will fry it.

If you did, start over with new SMPS units (you can't trust even the one that showed no damage now), and this time do a search on what you want to do and how to do it right before you start.

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JRaef
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#7

Re: Please reply fast , its an emergency.

12/14/2012 4:14 PM

To wit:

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Joshi
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#8

Re: Please reply fast , its an emergency.

12/15/2012 3:27 AM

Research your problem out with these.
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Joshi
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#9
In reply to #8

Re: Please reply fast , its an emergency.

12/15/2012 3:31 AM

If you can post circuit schematic & furnish all relevant details, it may be possible to analyse, the causes of resistor failure.
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PWSlack
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#10

Re: Please reply fast , its an emergency.

12/16/2012 10:49 AM

What's urgent about that?

Simply, the resistor was unable to survive the current being passed through it. Look for situations where too much current could have been the cause.

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jack of all trades
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#11

Re: Please reply fast , its an emergency.

12/16/2012 2:09 PM

What would be reason for that?

a) You wired up the equipment incorrectly and it blew up

b) The SMPS supplies and/or circuit are not designed to be connected in series and blew up.

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Users who posted comments:

Doorman (1); jack of all trades (1); Joshi (2); JRaef (2); lyn (1); PWSlack (1); redfred (1); Yahlasit (2)

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