This guy is from a dishwasher control panel. I'm having trouble finding a replacement for the entire control unit (that will ship to Japan, anyway) and I am handy with a soldering iron.

Can you take a stab at what you think it might be?

a wider shot, but a bit blurry

original cropped

Replacement Board

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    \$\begingroup\$ Show us photos of Q1, Q2, Q4 ... please? \$\endgroup\$ – skvery Mar 31 at 9:59
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    \$\begingroup\$ We don't have permission to view the image, so don't put it behind a firewall if you want us to help you. \$\endgroup\$ – Edin Fifić Mar 31 at 10:43
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    \$\begingroup\$ Do you know why it performed its own spontaneous disassembly? If the cause isn't fixed a new one will likely do the same thing. \$\endgroup\$ – Colin Mar 31 at 10:58
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    \$\begingroup\$ @Colin it difficult to see, but the back tab might not be properly soldered - maybe this caused the smoke coming out. I would recommend that he orders two replacements. \$\endgroup\$ – skvery Mar 31 at 11:01
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    \$\begingroup\$ By any chance is there a part nearby shaped like this that may have similar evidence of trauma? \$\endgroup\$ – Spehro Pefhany Mar 31 at 13:19

It's made by ST Microelectronics based on Logo.

The package is indeed DPAK (TO-252)

Based on the pinout, it's not a MOSFET (either P or N). All of the ST MOSFETs in DPAK have the gate on pin 1 (lower right in the picture orientation), which makes no sense. The control line of this device is pin 3.

This leaves something like a TRIAC or SCR. The DPAK offerings from ST do have their control line an pin 3, so that looks good.

Beyond that with the markings gone it is hard to tell.

Based on other DPAK parts, the part number is split onto two lines. The first line is the series number, the second line is the rest of the part number.

From your part we can make out very little


The exact number of digits vary.

One option that fits that bill are the T4 series 4A logic level Triacs. These have part numbers that seem to match. For example this one looks pretty darn close to your image.

Similar Triac Part Image Source

Looking closer at your image, we can make out something just before the 4 on the first line which could well be the T.

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    \$\begingroup\$ Top sleuthing Tom! @PlanB do you have photos of any other similar-looking parts on the board? \$\endgroup\$ – jonathanjo Mar 31 at 12:24
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    \$\begingroup\$ Man, Tom, that's just awesome! I knew that there were not going to be alot of variables in this form-factor, I just don't know components enough to do the great work you did; Thanks so much! I can probably pick one up in Akihabara. \$\endgroup\$ – PlanB Mar 31 at 15:22
  • \$\begingroup\$ Unfortunately, on the board there are no other packages that size, nor any with the same logo. However, Tom's guess is probably accurate. In my feeble search, I didn't see any other '252 with a 4 as the last number. \$\endgroup\$ – PlanB Mar 31 at 15:26
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    \$\begingroup\$ @Charlie Frequently but not always. You can't always rely on the refdes label to identify the component type, people use weird choices at times. But when it comes down to it, a triac is basically a weird stacked transistor. \$\endgroup\$ – Tom Carpenter Apr 1 at 11:44
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    \$\begingroup\$ @PlanB: Well, you can't break it anymore I guess ¯_(ツ)_/¯. Ganbatte tomoyo. Don't electrocute yourself. \$\endgroup\$ – Charlie Apr 1 at 12:15

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