speed control switch

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mock

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Can you change a speed control switch on a diamond fret saw If so how and where to purchase a replacement thanks in anticipation Mock
 
Just opened mine up, there are a few photos below. I'm not entirely clear what needs replacing, the switch or the speed control? The speed control is a 250K linear pot, since it is wiring as avariable resistor as opposed to potentiometer I'd try to match that resistance value. Shaft is 1/4" D flatted. I measured 14.4mm from end of shaft to top of bush but looking at data sheets it appears the length is taken to the bottom of the bush. https://cpc.farnell.com/bourns/93r1a-r22-a22l/potentiometer-linear-250kohm-10/dp/RE07611 would be a suitable replacemnt alebit with 6mm round shaft so you'll need a new knob to fit it, e.g. https://cpc.farnell.com/multicomp-pro/mp1611/knob-25-4mm-w-dot-6mm-screw-black/dp/SW05902

OTOH if you really mean the switch it's just a 6A rated SPST toggle. Didn't have the right wrench handy to pull out the switch from the panel but the lock nut is 16mm diameter. Suitable replacement would be https://cpc.farnell.com/multicomp/mcr13-5-05/switch-toggle-spst-off-on-so/dp/SW05738

Interesting to comparing the innards of this saw with the Excalibur saw that came up elsewhere here recently. This one doesn't even have a circuit board, just a switch, a pot and a completely integrated phase angle controller, one of these: https://uk.farnell.com/united-automation/csr604a/ic-power-regulator-6a/dp/1213082
 

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This shows one of the reasons this is the best saw ever built!!!
These components are a cheap and easy fix if they go wrong.
If a hegner Axminster or dewalt fail it costs a fortune to fix
 
Just opened mine up, there are a few photos below. I'm not entirely clear what needs replacing, the switch or the speed control? The speed control is a 250K linear pot, since it is wiring as avariable resistor as opposed to potentiometer I'd try to match that resistance value. Shaft is 1/4" D flatted. I measured 14.4mm from end of shaft to top of bush but looking at data sheets it appears the length is taken to the bottom of the bush. https://cpc.farnell.com/bourns/93r1a-r22-a22l/potentiometer-linear-250kohm-10/dp/RE07611 would be a suitable replacemnt alebit with 6mm round shaft so you'll need a new knob to fit it, e.g. https://cpc.farnell.com/multicomp-pro/mp1611/knob-25-4mm-w-dot-6mm-screw-black/dp/SW05902

OTOH if you really mean the switch it's just a 6A rated SPST toggle. Didn't have the right wrench handy to pull out the switch from the panel but the lock nut is 16mm diameter. Suitable replacement would be https://cpc.farnell.com/multicomp/mcr13-5-05/switch-toggle-spst-off-on-so/dp/SW05738

Interesting to comparing the innards of this saw with the Excalibur saw that came up elsewhere here recently. This one doesn't even have a circuit board, just a switch, a pot and a completely integrated phase angle controller, one of these: https://uk.farnell.com/united-automation/csr604a/ic-power-regulator-6a/dp/1213082
 
This shows one of the reasons this is the best saw ever built!!!
These components are a cheap and easy fix if they go wrong.
If a hegner Axminster or dewalt fail it costs a fortune to fix
They may be cheap and easy to fix, but only if you know what you are looking for, how to test it and where to source the individual replacement component.
Unfortunately the number of people who fall into this bracket are getting few and far between.

Colin
 
had a little go at the diamond scroll saw earlier today when the saw started up the speed control was working but soon went back to normal full speed any idea why before I order new parts Mock
 
Sounds like a worn pot. The giveaway would be if it happens again tapping the speed knob or giving it a tiny speed tweak puts it back at the right speed.
 
Today it struggled to start but when she started the speed control worked again but only for a short period of time could it be the brushes
 
If you can give the pot a spray of WD40 into it then turn the knob a few times to help clean the contact inside tap it on a towel a few times then try to run it again.
 
Running ok today sprayed WD-40 on the contract s and speed control knob that turns the spindle on the controller ok but still does not control the speed sadly
 
A well known (and very simple) circuit- it is almost certainly the pot at fault (it could be a cracked carbon track- again common in higher value pots as it is a very thin film of carbon indeed, easily damaged)- replace with any 250K linear pot that physically fits as when being used with a 604A power reg chip or its 'bigger brothers', if it goes open circuit it goes to full speed(if you get a 'fluted' shaft instead of a 'flat keyway' shaft or vice versa, you may need a new knob in some cases though lol)
(WD40 isn't a good choice for cleaning pots- proper 'contact cleaner' readily available is better)

A new pot isn't much and can be replaced in under a minute with only two soldered connections... (and only a couple of pounds)

If not, the 604A is faulty, and they are again readily available and cost about 20-25 pounds for the 6A version

These are a great little unit suitable for direct replacement in many uses where the mains voltage needs to be varied, as they can be used with lamps, transformers and most inductive loads (fans, motors, etc) giving 0%-100% output- that is the 'baby' version rated at 6A, also available rated at 10A and 16A versions for bigger motors...

(Commonly used both as OEM circuits, and great for replacing most factory speed controllers as they are literally so simple to hook up- also handy for varying the speed on most motors where they didn't have one to start with as it literally goes in the Line wire in series and has a total of 3 components needed (one is 'optional' but good to have ie the 'SCR fuse' ie 'semiconductor fuse' - indeed there are versions available that are designed to mount directly to the pot itself, making fitting it on a 'non speed controlled' motor as simple as cut one wire, fit in series to the motor and drill a hole for mounting your new speed control circuit)

Screenshot from 2023-11-28 05-07-58.png


As you can see from the datasheet above, the pot is put across pins 1 and 2, with the incoming mains Line on pin 2 as well, and the motor connects to pin 3...

Personally I prefer to use an 'insulated shaft' pot in this application (many cheap companies don't, and rely on the plastic of the knob) as that pot is connected directly to the mains... any internal failure could see mains on the pot shaft in many cases!!!)

But as I said, a great little IC for making practically any motor 'speed controlled; or as a replacement unit for some overly complicated factory OEM circuits that cost mega $$$ for replacements- it is very close to being a 'universal' motor controller....
 
When my Diamond speed controller failed some years ago Doug Woodward (the manufacturer) sent me a free replacement tyristor to fit, Unfortunately Doug is no longer with us but you should find it easy to replace.
As you can see from the pictures AJS posted it is very simple and if your saw works fine on full speed it can only be the controller faulty.
The Diamond uses a series wound or universal carbon brush motor which are easy to control. If you are stuck you may be able to bypass the original and use an alternative Variable speed controller.
 
Just opened mine up, there are a few photos below. I'm not entirely clear what needs replacing, the switch or the speed control? The speed control is a 250K linear pot, since it is wiring as avariable resistor as opposed to potentiometer I'd try to match that resistance value. Shaft is 1/4" D flatted. I measured 14.4mm from end of shaft to top of bush but looking at data sheets it appears the length is taken to the bottom of the bush. https://cpc.farnell.com/bourns/93r1a-r22-a22l/potentiometer-linear-250kohm-10/dp/RE07611 would be a suitable replacemnt alebit with 6mm round shaft so you'll need a new knob to fit it, e.g. https://cpc.farnell.com/multicomp-pro/mp1611/knob-25-4mm-w-dot-6mm-screw-black/dp/SW05902

OTOH if you really mean the switch it's just a 6A rated SPST toggle. Didn't have the right wrench handy to pull out the switch from the panel but the lock nut is 16mm diameter. Suitable replacement would be https://cpc.farnell.com/multicomp/mcr13-5-05/switch-toggle-spst-off-on-so/dp/SW05738

Interesting to comparing the innards of this saw with the Excalibur saw that came up elsewhere here recently. This one doesn't even have a circuit board, just a switch, a pot and a completely integrated phase angle controller, one of these: https://uk.farnell.com/united-automation/csr604a/ic-power-regulator-6a/dp/1213082
new switch and speed control switch replaced still no joy next : https://uk.farnell.com/united-automation/csr604a/ic-power-regulator-6a/dp/1213082 £27 odd i think ill sell it on but tell them about the problem we will see thanks for your help Mock
 
new switch and speed control switch replaced still no joy next : https://uk.farnell.com/united-automation/csr604a/ic-power-regulator-6a/dp/1213082 £27 odd i think ill sell it on but tell them about the problem we will see thanks for your help Mock
That is a great shame. the Diamond is a well made saw and has no complex electronics to worry about as found in some of today's machines, because of this they are cheap and simple to repair. apart from the switch, speed control the motor and some wiring there is nowt complicated about the saw.
Because the Diamond uses a series wound carbon brush motor and your speed control wont work it would be simple bypass the original and use a non standard variable speed control with this saw.
 
The electronics are as simple as it gets in these.
I'd spend the money and swap the 604A.
If you want to be really sure there is nothing else left that it can be, just connect the motor directly to a flex and plug, turning it on and off at the socket. If the motor is good and you've swapped the pot and switch, then it can only be the semiconductor, or a maybe an intermittent break somewhere in the few inches of wiring.
 
What jumped out for me is that earth terminal, I hope that is not the only connection to ground for the machine as the box is polycarb / abs and if that is the only earth connection then in my opinion it is very poor as it relies only on the nut / washer at the back.
 
Looks like the bolt being used as the earth terminal is one of two mounting bolts that secure the plastic box to the metal behind it. I'd expect the bolt or machine screw to be going into a tapped hole in the metal bodywork.
 
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