Removing the speed control from the motor depends on the type of motor used.

If its a pemanent magnet motor, you will need to feed the motor with high voltage dc to get it to run ( high voltage means greater than 12v……) if its a universal motor, then simply connecting mains 240v ac will get it to run…..

If its an induction motor……well lets see what you come back with..with regards to the type of speed control thats fitted..

Might be a dirty speed control pot?

Having seen the picture I think Neil is correct. If you unplug the saw, then open up the box with the knob on the front and you will see what looks like a volume control and on the back of it (if you are lucky) will be its value in Ohms. For example 10K Lin. You can buy a replacement from several suppliers on line RS, Farnell, Rapid or ESR., it must be a Linear type (Lin ) Or, if you know of an electronic repairer a quirt with their RS switch cleaner might solve your problem. John

bear this in mind if you want it flat out all the time

All these cheap scroll saws i have seen vibrate like mad..very poorly constructed and balanced they need fastening onto a thick felt cushion

Some pots have lin or log printed on them some have an A for analogue or a B for linear .

Does the speed keep changing with any sort of regularity or settle down after a few minutes ?

You really do want to keep the speed control function on the saw as it makes them more usable , sometimes you want to slow things down for delicate work etc .

It could as neil suggested be a crook pot or it could be a crook connection or dry solder joint , the only way to check it is to pull it apart and have a look .

Edited By XD 351 on 30/06/2018 08:24:36

I think it is unlikely to be the pot (potentiometer) but if you want to test it…

The speed pot has 3 connections. Disconnect the middle connection (black) and connect it to one of the other pot terminals (also connected to red wire) and run it – you should get either max or min speed depending on which end.

Then do the same but connect to the other pot terminal (also connected to blue wire) and run it again.

Leave red and blue connected to the pot at all times.

This will give you max and minimum speeds. If still not stable in speed it is 99.9% certain not the pot. If it is stable then change the pot – the value is written on it and plenty on ebay.

Edited By Clive India on 30/06/2018 09:52:51

Misbehaviour when the board is vibrated suggests a loose connection or bad joint. For example an intermittent on the either of the max or min pots would cause the control range to float and confuse the poor thing.

Try flipping the board over and checking with a magnifying glass for dry joints, cracks between joints and board or components and – less likely – tiny whiskers of solder bridging any connections. This link has a good overview.

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Great result

MichaelG.