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DanielSimao
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Join Date: Aug 2011
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Polar Mohr Etromat 72

09/01/2011 7:09 AM

Im still having issues with my 72. I replaced a burnt resistor and it keeps melting down on me. Does anyone have any idea what might be causing this issue? Its a 47 ohm 11 watt resistor that I replaced it with. Any help would be appreciated.
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PWSlack
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#1

Re: Polar Mohr Etromat 72

09/01/2011 7:42 AM

What is the voltage across the resistor?

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DanielSimao
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#2
In reply to #1

Re: Polar Mohr Etromat 72

09/01/2011 7:56 AM

209 v
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PWSlack
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#3
In reply to #2

Re: Polar Mohr Etromat 72

09/01/2011 7:58 AM

OK. Here's a clue. (209V^2)/47Ω = 929W.

929W/11W = 84-odd. Either the resistor is undersized by that factor or the voltage is too large by the square root of it.

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PWSlack
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#4
In reply to #2

Re: Polar Mohr Etromat 72

09/01/2011 8:23 AM
  • Is there a 24V power supply that has gone phut somewhere, and that is taking pseudo-mains voltage and shoving it across this resistor instead? It cannot be a design fault if the equipment has been working up until the point where the resistor went phut for the first time. What does this resistor do and why is it "seeing" 209V?
  • If the current is nine times normal, why didn't some protection circuit work somewhere to protect the electronics?

These are the sorts of things that need investigation.

http://www.polar-mohr.com/kontakt/index_en.html may be able to help too.

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DanielSimao
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#5
In reply to #4

Re: Polar Mohr Etromat 72

09/01/2011 8:52 AM

I found this info on another thread.

The transistor on the power board #3 was bad and not giving 25 volts.(control voltage)

I replaced both transistors while I was at it, I now had the 25volts, and it worked.

The resistor on board 22 is the charge resistor, for the stop capacitor.

I think this sounds exactly what my problem is. Polar Mohr is no help. Tried already. My problem is that I know very little bout electronics and not sure what the transistors even look like. I see 2 heat sinks 3 capacitors and a bunch of resistors and 2 potentiometers
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PWSlack
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#6
In reply to #5

Re: Polar Mohr Etromat 72

09/01/2011 8:53 AM

Bingo.

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DanielSimao
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#7
In reply to #6

Re: Polar Mohr Etromat 72

09/01/2011 8:54 AM

If I email you a picture do you think that you could help me out with what I need to replace?
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