Fan mosfet Q27 for Duet3 MB 6HC

3hristian

Hello,

I have found many topics related to Duet2 mosfet repairs and possible part numbers for replacements. There is even an article in the Duet3D Documentation.
(In case someone is searching for that: https://docs.duet3d.com/en/User_manual/Troubleshooting/Parts#fan-mosfet)

Thanks for that great community support by the way!

In my case, unfortunately I probably have a blown fan mosfet on my Duet 3 MB6 HC (v1.0) board for fans 6 and 9. This guess comes from the fact that both fans are now permanently on and not responding to control instructions.
Now I would like to replace the mosfet, but I am having a hard time finding a suitable replacement part. Apart from that, I haven't tried to replace such small SMD components yet either and would be grateful for any tips. Otherwise I would probably try a tweezer soldering iron first.

Specifically, I'm talking about the 3x3mm Fairchild Dual Mosfet Q27. Printed on the component is the text "T18 1915".

It would be great if someone can give me a hint
for a reference source and a part number or similar. In the long term, maybe also the existing documentation could be expanded accordingly.

Many thanks and best regards!
Christian

dc42

@3hristian the part number for that dual mosfet on the v1.0 board is DMT6018LDR. Unfortunately these are very hard to find at present due to the ongoing chip shortage.

Which country are you in? Please add it to your profile, if you are happy doing that.

To replace a small SMD component like that you would need a hotplate, hot air desoldering equipment, and a means to protect the adjacent connectors from the heat.

3hristian

Thanks for the quick reply dc42! I am from Germany :). Unfortunately the DMT6018LDR seems to have a lead time of a year or so at the well known distributors here...
Also thank you for the short description of how this component might be replaced.

Best regards
Christian

dc42

@3hristian if you were to send the board to me then I might be able to replace the mosfet because we have some stocks of that part. Unfortunately, Brexshit makes that cumbersome and probably uneconomical.

3hristian

Thanks for the great offer dc42! Before I might come back to that offer I may have another idea:

Because a possible workaraound (although not as nice) that might make my machine useful (even if with restrictions) again, could be the following:

I have a mains powered heated chamber in my printer. I control the heaters for that with a SSD relay (crydom A2450), which draws a maximum of 12 mA as input current. At the moment I also use a fan output to control the relay.

I could free the IO_5 port on my machine (which is able to generate a pwm signal). But I think that the direct connection of the relay (without additional transistor stage) is not possible, because the 12 mA are too much for a general IO port on the Duet3 MB 6HC? (I could not find any information about this.)

Am I correct at this assumption? Or asked in another way (for others maybe an even more helpful information): How much current can an IO_X port on the duet deliver?

Best regards and thank you very much!
Christian

dc42

@3hristian said in Fan mosfet Q27 for Duet3 MB 6HC:

I have a mains powered heated chamber in my printer. I control the heaters for that with a SSD relay (crydom A2450)

Did you mean D2450? The A2450 has AC control input.

Are you using the PS_ON output? If not then you could use that to control the SSR.

The IOx_OUT ports have a 470 ohm series resistor to offer them some protection against miswiring, so not suitable for providing 12mA. You could use a small mosfet or NPN transistor to drive the SSR from the IOx.OUT port.

3hristian

Oh, yes. Of course it's the D2450!

I just connected the SSD input to the PS_ON output. (I had completely forgotten about that port - thanks for pointing out!)

With this I can workaround the broken transistor for the important fan of my machine. I'll just run the other fan as always on fan from now on (it's just an aesthetic and not a functional flaw for my machine).

Thanks for the help and your offer with which I do not want to bother you now. It's fun to be (a small) part of such a community and to buy products from a company with this kind of customer support!

Best regards!
Christian