Dremel scroll saw speed control board

My first action would be to contact the mfgr and see what replacement parts are available and costs, etc. Also ask for a schematic. Try Googling on the model number.

H.R.(Bob) Hofmann

If they sanded off the numbers they most certainly won't supply a schematic.

I'd first suspect cracked solder joints, if those are all ok then look into the power component, almost certainly a triac which controls power to the motor. If all else fails you could build a new speed control from scratch, they need not be very complicated.

J is correct ... of components - look first at the Triac .. most TO-220 versions are 400 V or 600 V models at no more than 4 to 8 amps.

gb

Have you checked for bad solder connections?

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Thanks for all the responses so far. I have already gone over the board checking solder joints. Actually that is the funny part cause the fellows I work with say I must have microscope eyes since lots of the stuff we work on I can pick out bad solder joints with one eye tied behind my back ;-) I haven't really had time yet to check out the triac on the board or any of the transistors and stuff. During the brief time I saw the board I just happened to notice the chips sanded off so I thought I would ask if anyone had a schematic so I can have all my info handy before I start working on it later in the week. I have found places that sell the board for around $60.00 so if all else fails the owner can get another board. I'm on days off at the moment and I'm back to work on Tuesday so that is when I will get my hands on it again to start checking out the board at component level. Like I said, I was just seeing if I can get all my ducks in a row beforehand to make life a little easier. Thanks again folks.

Cheers, Lawrence

Oh boy, the days when I could spot a bad joint at 100 paces ... I'm lucky now to be able to spot one at 100mm without my specs !!

Sometimes, when these jokers sand the tops off of ICs, they don't do a very good job. On many occasions, I've been able to recover at least a partial number by moistening my finger tip, and just wiping it across the top of the IC, whilst shining a strong light at it. Sometimes, something more oily does the trick. Worth a try.

Arfa

Thanks for the reminder. In the past I have used a bit of mineral oil or instrument oil for flight instruments (I am a flight simulator tech) to brighten the chip markings so they were easier to read. It is rare that I come across sanded chips so I had forgotten all about that until your mention of something oily. Thanks again.

Cheers, Lawrence

Arfa Daily wrote:

Here's my update and simple fix for the problem. Initially I was just shown the speed control board just to see if I would be willing to have a go at it. This is why I was looking for access to a schematic out there. Anyway, I said sure so the person brought me the whole saw. I popped open the switch panel on the saw and found a wiring problem so it turned out to not be the control board after all. It seems the owner was cutting something and the saw popped its lock. The owner reset it and it popped again. The owner thought it might be something happening behind the switch panel so he popped it open. In the process he accidentally switched one of the wires going to the power switch with one of the wires going to the light bulb switch. At this point the saw wouldn't work at all when he switched it on. Thank God he had only switched the two wires he did. If he had switched any other wires he would have had a pretty loud bang when he tried to power the saw on since he would have created a dead short in the AC line and it probably would have knocked him ass over teakettle. Anyway, I swapped the wires back to where they should be and everything was good again in a matter of a couple of minutes. I know some people take offence when they ask a question and have other people tell them to keep their noses out of it or they might get hurt. Most times I don't think the ones saying to stay out if not experienced are being cruel or anything like that. They are just trying to help prevent someone from getting seriously injured. So, if you are reading this and you don't consider yourself to be experienced in repairs then please take the time to seek good help before tackling what may appear to be a simple task yourself. The fingers you save just might be your own.

Cheers, Lawrence