The wizard of woz
Malcolm, it's worth swapping the tip for a 1mm one just to see if it has any effect whatsoever on your problem.
No noticeable resistance there to start with, but a new tip with the 0.8 wire made no difference. I normally find the resistance increases when the tip and wire gets hot - can grab if you really heat them up.
Malcolm, what is the part # on the transistor? Hope it is something like LM317 (voltage regulator) instead of just a transistor like the SIP's use. Probably a common part.
rtbcomp, that is a variable voltage drop. It sets drops the supply voltage by a fixed amount. It is effected by the gain of the transistor that changes with temperature. Does not regulate the motor voltage well.
I have to say malc, If this was one of my machines I would have got the manufacture to sort it, even on the simplest of thing's never mind buggering about with PCBs...Murex sorted me parts FOC even tho, the machine was 10 years old....a simlar story with cebora over an inverter.... Ring em up say its broke, get em to fix it.
Felt it would be a hassle returning the whole thing - would need to post it so need to find a big box and be at home for a day for a transport company to pick it up so a days earnings lost. If I can figure out which bit to ask for I could get that posted here.
Yes, looks like they use pulse-width to control the speed of the motor. I would have expected better for a higher-end machine.Strange that it didn't happen from new and that nobody else spotted if it's a design fault. I think something has broken somewhere on my machine.
Here's the transistor. Looked it up - it's a Thyristor - posh! Suggested applications include motor control.
Yes, looks like they use pulse-width to control the speed of the motor. I would have expected better for a higher-end machine.
Thyristors don't like inductive loads like motors. Takes a considerable amount of circuitry to do them well. Looks like the same circuit I saw on one of those Wolf welders
I'ld just replace the board. I would check the brushes first. If they are noisy they can make these circuits unstable.
Don't use the SIP circuit!