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Bell Carrol Plasma Cutter - Cut 40

AprilSteel

Feb 2, 2017
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I have one of these that used to work great then developed a problem with the starter circuit.
It does not ignite the plasma even though the sparks between the contacts are good . If I touch the torch to ground without the ceramic tip I get a spark. But when its all as it should be it seems that the starter spark is just not strong enough to get across to the job. The two caps carrying the starter current measure 100mF and bothe of those dirty looking resistors seem to measure OK

Ill add a couple of pictures and maybe someone is familiar with the starter circuit?
IMG_20171101_170125.jpgIMG_20171101_170106.jpg IMG_20171101_170132.jpg
 

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kellys_eye

Jun 25, 2010
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Have you checked that there is no leakage to ground anywhere? Some of the circuitry around the voltage multiplier (the 'string' of diodes and capacitors) seems pretty gunked up and the ends of the big resistors look a bit suspect.

Assuming everything is clean and there is no leakage/flashover then the capacitors may be suspect - despite their measurement.
 

AprilSteel

Feb 2, 2017
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Thanks I did replace the closest resistor as it was measuring in the megohms instead of 150k 5 watts ,but nothing has changed. The bad looking one tested fine. .Checked at night looking for any flashover but none I can see . Do you know what the circuit looks like for that bit? Is it an A/c flow low current high voltage ? and what sort of voltage should come out? Is it produced by a transformer and could that be shorted? Can it short in any way inside the back of the torch? I,m confident the front of the torch is right.
 

kellys_eye

Jun 25, 2010
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The spark looks to be generated from the items shown here:

multiplier.png

The yellow transformer output feeds the multiplier/rectifier circuit comprising the diodes and 'blue blobs' (capacitors). It will be high voltage and high frequency (input) and the transformer itself is fed from an oscillator circuit on its primary that 'may' be the cause of a low voltage output.

Is the big blue 'box' behind the transformer a capacitor or a relay? What do the markings say?
 

AprilSteel

Feb 2, 2017
111
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Feb 2, 2017
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Thanks . The blue is a relay . Ill pull the circuit board out again and check over and tell you the values then . Off to the Cup tomorrow so it will be a few days.

Oh that's the Melbourne cup in Australia..Horse race like the derby
 
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