Can't Slow Down

[etlcsns]

This is my first post so hello to everyone

I have a vintage SIP Handymig, and have been having wire feed problems, It will not slow down, the speed control does change the speed but only slightly. After going through posts here I found the trim pot on the PCB but it makes no difference at all, The Pot does have 100 written on it so I assume that is the value.

As usual I only noticed this when use is urgent, any ideas what is wrong?

 

[the snooper]

hi and welcome to the forum
you would need to test the pots with a meter to verify they are working correctly and any resistors then onto the other parts of the board

 

[etlcsns]

Thanks,

I have taken the PCB out and measured across the trim pot, and the readings don't change at all regardless of where it's set.

So I assume we have found the problem.

Maplins have a subminiature 100R pot, so I'll get one and fit it.

Is there reason this has failed?

 

[Robotstar5]

I have taken the PCB out and measured across the trim pot, and the readings don't change at all regardless of where it's set.

Did you remove the pot?, you may have been measuring other components connected to it via the PCB

 

[the snooper]

also pots have three connections two of which are the carbon track and when measured will give the value of it say 100 ohms and wont change regardless of position and the third (usually in the middle) is the variable connection and will change from a low resistance to a maximum of 100 ohms (value of component)

 

[etlcsns]

I noticed particles coming out of the pot when turned, so I removed it

Again no readings so i prised the end off and the carbon track has broken up completely, i'll post a photo tomorrow.

Also removed and tested the transistor which checked out ok, but I'll change it anyway.

Big thanks to every one who replied