MiG welder..... what is this component?

A

Andyr31

New Member

• Jun 20, 2018

• #1

what is the little yellow blob things here?

not the ones in the Pic but there is another broken one in series on the torch trigger wire.... is it a NTC resistor? if so what value would it be?
the machine is a BOC smootharc 350 there's a service manual available but it does have details of individual components.

 

A

Andyr31

New Member

• Jun 20, 2018

• #2

sorry. .. here is the Pic with the same looking yellow blobs.... (labeled RR1)

 

W

Western

Member

• Jun 20, 2018

• #3

Can you read any of the markings on them ... use a sharp blade and you may just be able to lift off the glue to see.

 

A

Andyr31

New Member

• Jun 20, 2018

• #4

no, the pic is of a pcb from the same machine, the one I part need to replace is inline on the wire to the torch switch, mounted inside the separate wire feeder unit. the broken part is damaged and illegible.

can you think what the purpose of it would be? I haven't come across any other welders with this..

 

camerart

Well-Known Member

• Jun 20, 2018

• #5

Hi A,
I get the impression, that the components is a Thermistor.
Looking at the manual: **broken link removed**

There is reference to RR on one of the pages and checking Thermistor symbols, they look similar.

hope this helps.
Camerart

 

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• Wire control.jpg

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• Wrie feed.jpg

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A

Andyr31

New Member

• Jun 20, 2018

• #6

yes I seen that, any idea as to purpose and value?

 

DerStrom8

Super Moderator

• Jun 20, 2018

• #7

My guess is they're PTC fuses (basically resistors that vary their value according to the current flowing through them). They are used for surge protection - if there is a surge of current their resistance goes up, limiting the current to the rest of the board. This protects the downstream components.

 

camerart

Well-Known Member

• Jun 20, 2018

• #8

Andyr31 said:

yes I seen that, any idea as to purpose and value?

Click to expand...

Hi A,
'D' may be correct!

If they are Thermistors, note on the schematic, that each has an arrow, one pointing in and one out. My guess is they are temperature resistors, one goes up and one goes down depending on temperature.

Try a search for 'your welder' plus thermistors, also images, in case you spot the same type.

Good luck.
C.

 

S

schmitt trigger

Well-Known Member

Most Helpful Member

• Jun 20, 2018

• #9

There is a "t" and a degree symbol next to it in the schematic.

But it does not list initial value nor temperature coefficient.

 

camerart

Well-Known Member

• Jun 20, 2018

• #10

schmitt trigger said:

There is a "t" and a degree symbol next to it in the schematic.

But it does not list initial value nor temperature coefficient.

Click to expand...

Hi T,
Yes, they are Ts, perhaps T for Thermistor?
C.

 

camerart

Well-Known Member

• Jun 26, 2018

• #11

Hi A,
Today I contacted BOC, and was told that this isn't a UK bought welder, so they don't have details about it. If this is correct, and you want to keep trying. I suggest you find out the supplier, open their webpage, see if there is a 'chat' and ask them.
Remember to say the details of RR1 and RR2 are not in the repair manual that you've got.
Cheers,
C.