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Bad Primary Switch (B2)

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Timer counting down but no fan and no power to magnetron Opened-up the unit, found signs of overheating on the

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  #1 (permalink)  
Old 11-15-2015, 08:56 AM
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mvuille is on a distinguished road
Question Bad Primary Switch (B2)
Model Number: MW6470W   Brand: Samsung   Age: More than 10 years   

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Timer counting down but no fan and no power to
magnetron

Opened-up the unit, found signs of overheating on the
quick-disconnect to switch B2 (primary switch)

Removed the switch and found that the N.O. terminal
has overheated, plastic switch casing is slightly melted,
switch no longer operates correctly (N.O. on only when
partially activated, off when fully activated)

I am thinking there are two possibilities:

1) quick-disconnect connection went bad over time, increasing
resistance, causing overheating, eventually resulting in the
damage I see

2) overheating and damage are a symptom of a short-circuit
or similar more serious issue

For (1), I can simply replace the switch and clean-up or
replace the quick-disconnect

I am more concerned about (2). How would I check for an
over-current or short-circuit?

MV


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  #2 (permalink)  
Old 11-15-2015, 12:22 PM
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Default Additional information

Measured the D.C. resistance of the low-voltage winding
of the H.V. Transformer and got 0.4 ohm. (This is with both
secondaries disconnected)

That doesn't seem reasonable, does it?

MV

Last edited by mvuille : 11-15-2015 at 12:32 PM.
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