Milwaukee Circular Saw MOSFET Failure- Need Replacement

[KDoug]

Hi,

I've posted this on another electronics forum, but I haven't got many answers yet. I figured I'd try asking Garage Journal because folks on here know a little bit about everything. So if anybody knows if the two parts I have linked below will work, I'd appreciate any input. Here's the link to my other thread:

http://www.eevblog.com/forum/repair...t-failure-need-replacement/new/?topicseen#new


I've recently bought a non working Milwaukee 18V cordless circular saw (Model 2630-20). I took a chance when I bought it knowing there was a possibility I wouldn't be able to repair it, but I like a challenge so I bought it anyways.

I took the saw apart and found two components on the board that have failed, which I later found out are MOSFETs. I've done a little reading online to get a basic understanding of what a MOSFET is, I don't quite understand what it does, but I know it has a drain, gate and source. I guess my biggest question is- what would cause this to fail? And if I replace it, will it fail again?

I did a quick google search with the writing on the MOSFET, which reads "F1404ZS". I've found two similar parts and need to know which ones will be the best option for me. Below is a link to the parts I have found:

https://www.digikey.com/products/en...f=0&quantity=&ColumnSort=0&page=1&pageSize=25

The two parts I have listed are made by Infineon, are there other brands I should be looking at? I didn't know how to filter down my options, because there are a lot of numbers and information on these MOSFETs and I really don't know what most of it means.

I have also attached some photos of the broken part. The writing reads F1404ZS, International Rectifier Symbol, 016P, TC, 3W

Thanks for help in advance.

 

[kctyphoon]

Milwaukee has a 5 yr warranty - and they still sell that saw, so you might have been able to Just send it in.. I’m not so sure we will be much of a help with this one.

If i were you, id send this info into Milwaukee customer service and see what they say.. they may even send you one of the parts for free.. or even a saw..

 

[woody 73]

See if anything in this link will help you out:

https://www.ereplacementparts.com/m...volt-circular-saw-parts-c-131_5128_16320.html


https://www.toolpartsdirect.com/milwaukee-2630-20-b57a-18-volt-circular-saw.html

 

[cuog]

Your failure was likely caused by a short, but its hard to know for sure.

Either mosfet you linked will work just fine(assuming the rest of the circuit is ok).

My biggest concern would be that basically every semiconductor on that board is dead. The little transistors on there are likely a bunch of cheap NPNs and may have also been fried. In my experience when a mosfet goes, the driving circuit is also taken out.

 

[KDoug]

Milwaukee has a 5 yr warranty - and they still sell that saw, so you might have been able to Just send it in.. I’m not so sure we will be much of a help with this one.

If i were you, id send this info into Milwaukee customer service and see what they say.. they may even send you one of the parts for free.. or even a saw..

Yes, I had thought about the warranty, would I have to send it in? Or can they send me a new electronics assembly? Those MOSFETs are about $2 a piece, so I may start with buying them.

 

[KDoug]

Your failure was likely caused by a short, but its hard to know for sure.

Either mosfet you linked will work just fine(assuming the rest of the circuit is ok).

My biggest concern would be that basically every semiconductor on that board is dead. The little transistors on there are likely a bunch of cheap NPNs and may have also been fried. In my experience when a mosfet goes, the driving circuit is also taken out.

Thanks, that was a bit of helpful information. I couldn't figure out the difference between the two parts I linked, did you notice any difference?

There's not that many parts on the board, I thought about buying each of those components if replacing the two MOSFETs doesn't work. I know how to find the resistors but I'm not sure how to find the other diodes (correct me if they're not diodes).

 

[one9gt]

Is that the switch assembly? If so, why mess around with mosfets when you can get a whole new switch assembly and board for $30?


Sent from my iPhone using Tapatalk

 

[kctyphoon]

Yes, I had thought about the warranty, would I have to send it in? Or can they send me a new electronics assembly? Those MOSFETs are about $2 a piece, so I may start with buying them.

You would have to see what they tell you. I’m sure not many people try to repair / replace electronics on their own. They might just tell you to send it in, for liability purposes, or they may just send you the part.. Customer service being what it is with them, i wouldnt doubt for a minute if they said they’d just send you a new saw.

 

[purplezr2]

Post the serial number so we can see if its under warranty still. If it is, I would just fill out the e service ticket and warranty it .

 

[Rabid Badger]

If you end up replacing the mosfets, just use the same parts that are on the board. Mouser has them for $1.71.

When you see mosfets blown like that it's usually due to a failed snubber diode. Look for a big fat diode on the switch assembly. Odds are it will be toast.

 

[KDoug]

If you end up replacing the mosfets, just use the same parts that are on the board. Mouser has them for $1.71.

When you see mosfets blown like that it's usually due to a failed snubber diode. Look for a big fat diode on the switch assembly. Odds are it will be toast.

Where are you talking about? The picture I posted is all the electronics there is. I did look up one Schottky diode on the top of the picture if that's what you are referring to.

 

[gungatim]

I see 4 diodes D1 through D4.

being that is all surface mount stuff, I personally wouldn't mess with it and just get a new board.

have you ever solder surface mounted components? not something everybody can just do.

you also need to test each part of the circuit, diodes, resistors, caps, etc.

and then make sure the new transistors are properly bonded to the heat sink. honestly not worth the effort IMO.

keep you eye out at the local flea market or junk store and you may get lucky and find another saw you can scavange parts off of. when the batteries go bad, the tools become nearly worthless to most people...

 

[DFB]

Ya really what is the date code in the serial number first of all. Why mess with it if they'll fix it for free.

Board failures are pretty common on these tools. I have already had two tools repaired that way and just sent out a 3rd. Milwaukee normally just replaces the whole board.

Heat or vibration is what usually kills board components.

Since I had a long career in electronic component I'm now quite curious about the Life Test expectancy results of their contracted parts, seeing that they fail quite often. But on they other hand 5 year warranty is the general indicator.

My 3 tools all went down around the 4 year mark

 

[Davefr]

Where are you talking about? The picture I posted is all the electronics there is. I did look up one Schottky diode on the top of the picture if that's what you are referring to.

It also looks like that circuit board has damaged/burn out traces. Get the P/N and order the complete assembly from Ebay.

The individual components might be cheap until you get ready to checkout and see the shipping/handling charges and min. order thresholds.

 

[KDoug]

I see 4 diodes D1 through D4.

being that is all surface mount stuff, I personally wouldn't mess with it and just get a new board.

have you ever solder surface mounted components? not something everybody can just do.

you also need to test each part of the circuit, diodes, resistors, caps, etc.

and then make sure the new transistors are properly bonded to the heat sink. honestly not worth the effort IMO.

keep you eye out at the local flea market or junk store and you may get lucky and find another saw you can scavange parts off of. when the batteries go bad, the tools become nearly worthless to most people...

Yes, I know soldering surface mount components is a pain in the but. I don't have much experience but I did make a repair to a Dewalt Oscillating tool last year. I had chipped one of the resistors trying to take the tool apart. I was able to find a replacement online and soldered a new one on. It was extremely small and had 6 pins, I had to drag solder it on.

 

[sweet victory]

This is what happens when we stay up all night watching AvE. haha Probably best to let the OEM take care of you if it's under warranty.

 

[American Locomotive]

A MOSFET is an electronic switch. You apply a small amount of power to one pin, and it allows a much larger amount of power to flow through the other pins.

Usually when a MOSFET explodes like that, it means something shorted out. It might be worth a shot to replace the mosfets if you're looking to have some fun, but it's possible something else has died as well.

 

[DFB]

All Milwaukee requires for warranty is for you to read the serial number to them. If it's within the warranty period they fix it 100% free.

May not always be free as they do get the final call on the reason for the failure, (abuse, negligence water intrusion etc. is normally not covered) though they are pretty good about warranty work.

But even if they do not cover it under warranty they also give you two options, one to promptly repair it under their speed service program or you can have it returned at your cost if you like otherwise they dispose of it.

 

[KDoug]

This is what happens when we stay up all night watching AvE. haha Probably best to let the OEM take care of you if it's under warranty.

Ha Ha. Yeah, I'm in a little over my head, but I figured if I learn anything it would be worth it.

I did contact Milwaukee this morning, I'm waiting on their response. My serial number starts with B57A.

 

[KDoug]

Here's a good reply I got last night on the EEV Blog:

+1 to everything T3sl4co1l posted.

It's ok to change just the FET and try again, though. If the thing doesn't work anymore, then work your way back and hope you can find the driver and other parts.

There are a lot of specs on a FET, and most of them don't matter for this use. In this case, it's just a switch to turn the saw on/off. The main reason a physical thumb switch doesn't just turn the saw on/off, directly, is the circuit board has to also be able to cut power when the battery runs low to prevent the battery from being a single use item. And the circuit probably also switches off the power in case the motor draws too much current (like what would happen if you were to stall the blade in something), which could irreversibly damage the battery and/or the motor. For the circuit to do that, it uses the FET as a switch, since it can't flip a thumb switch like you can.

If you get the idea that you could just trash the board and replace it with a physical thumb on/off thumbswitch and some common sense, I didn't say it. It would be real easy to overdraw the battery and damage it. It would be somewhat feasible to make your own protection circuit with low voltage cutout and reset as a learning experience, but it's highly unlikely the saw itself is worth that much time in the end.

Brand names don't really matter, so long as you buy it from a regular component retailer and not eBay or Alibaba. Most of the specs don't matter to you other than

1. Correct package. Same package as the one you removed from the board, whether that's a TO220 or Dpak or whatever it is.
2. Rds on, resistance between drain and source.
3. Max voltage of 40V. Don't go too much lower. I bet 30V would work. You could go higher, but it would probably results in worse specs for no reason. 30-40V is fine.
4. Peak current draw. The peak is going to be pretty high in any inductive load, like this. Stick with 750A peak minimum.

The constant/static current draw is also important, but take that with a grain of salt. What you really care about is the package is the same one that came off the PCB and that the Rds is about the same as the original. If the constant/static current draw is rated higher than the original part, but the Rds is also higher, then it is not going to be "better" and it may die, prematurely.

You could go a bit smaller/lower on the Rds than the original without too much issue, but that might affect the cutout voltages of the protection circuitry.

Most of the other specs shouldn't really matter for this purpose. I'd ignore every other spec and just sort by price.

 

[DFB]

For the 5 year warranty purposes without a dated purchase receipt the serial number daycode Milwaukee goes by will be the 4 numbers (yr/mo) following the first four digits.

All the current Milwaukee tools are like that.

 

[KDoug]

I forgot to provide an update with what I ended up doing. I got my parts in from Digikey a little over a week ago and soldered the new MOSFETs on. To my surprise the saw actually ran, but I'll have to use it on a few projects before I can confirm it's really fixed. The two MOSFETs were $2.28 each and shipping was $5. So for less than $10 I was able to fix it.

For those wandering, I did go through Milwaukee, but they pretty much gave me the standard answer, which was to send it in for repair. I might end up doing that if this isn't a long term fix.

Thanks to all who commented and gave me advice.

 

[KDoug]

Here is a picture:

 

[outdoorspace]

Good job, I fixed my Ridgid saw (which is brushless) the same way. Too many heavy cuts in wet PT.

Another important MOSFET parameter is the gate charge, or Qg. If it's too different the transistors could get a lot hotter. Qg affects the power dissipation during the PWM transitions.

 

[KDoug]

Good job, I fixed my Ridgid saw (which is brushless) the same way. Too many heavy cuts in wet PT.

Another important MOSFET parameter is the gate charge, or Qg. If it's too different the transistors could get a lot hotter. Qg affects the power dissipation during the PWM transitions.

Thanks, I'm starting to dabble around with repairing electronics. I'd like to know enough to take the mystery out of it a little bit and fix basic stuff that most people would throw away.