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Its a turn Knob switch for setting timer and push start in Samsung microwave oven I also want to desolder this component. How to do that?

enter image description here enter image description here

enter image description here enter image description here

https://www.buyspares.co.uk/microwave/mw87l-mw87l-bxeu/assy-key-module-dkm-mw87l-key-module/product.pl

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  • \$\begingroup\$ Given the hell this poor board appears to have been through, you're probably best off just buying a new board, though that board currently seems hard to find. I don't suppose you're in the US are you? I suspect the problem is one of the damaged traces on the board, rather than the switch itself, unless you can mechanically feel it doing something it shouldn't, or not doing something it should. \$\endgroup\$ – Doktor J Jul 17 at 19:33
  • \$\begingroup\$ Switch is bad, I tested the connections, I am from Pakistan, can't find new / spare board in market! Samsung shouldn't use this type of component that is hard to find :) I am planning to bypass this encoder switch only, but can't find the traces! \$\endgroup\$ – Muhammad Sannan Khalid Jul 19 at 9:08
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    \$\begingroup\$ Ah. Unfortunately it's likely a proprietary part -- in this case I suspect it's more that a standard part didn't already exist (number of contacts, pushbutton functionality, encoding type, etc). You'll likely have to drill out the four rivets and heat the board to get to the surface-mount contacts. Worst case scenario you can sand the solder mask off one of the traces and solder to the trace outside of the broken switch. The trick will be in figuring out how the switch connects, electrically speaking. \$\endgroup\$ – Doktor J Jul 22 at 14:33
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It is probably a rotary encoder with a switch.

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  • \$\begingroup\$ Ok. do you know how to SALVAGE this component? I want to install new one \$\endgroup\$ – Muhammad Sannan Khalid Jul 17 at 9:55
  • \$\begingroup\$ I don't really understand your question. To replace it you would desolder the existing part, and solder in a new one. \$\endgroup\$ – Colin Jul 17 at 9:56
  • \$\begingroup\$ Yes, I want to replace it, but I can't find soldering points, please see updated image above post! \$\endgroup\$ – Muhammad Sannan Khalid Jul 17 at 10:10
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    \$\begingroup\$ I'd guess that there are no solder points, there's a body with the rotor in it, riveted to the pcb, and that rotor has spring contacts that bear on pads directly printed on the board i.e. the board forms part of the assembly and it won't be any use by itself - just like the snap action switches on that board, they will bear down onto pads printed in the board itself. \$\endgroup\$ – Phil G Jul 17 at 20:56
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    \$\begingroup\$ @PhilG: make that an answer. I'd say you've got it. \$\endgroup\$ – Transistor Jul 18 at 17:06
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It looks like it is a rotary encoder riveted to the copper side of a single sided board. You could drill/grind the rivets from the back of the board and see if the encoder detaches. It might not be soldered on. If it is, you might need a hot air gun to desolder it.

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  • \$\begingroup\$ Interesting. It's first time I see [or hear about] a throughole component riveted to a single layer board. \$\endgroup\$ – Nick Alexeev Jul 17 at 22:39
  • \$\begingroup\$ @NickAlexeev It doesn't look like it is a throughole component. There are no holes for any pins. It is either just pushed against pads on the copper side like all of the push buttons, or it is soldered as a surface mount. \$\endgroup\$ – HandyHowie Jul 18 at 4:45
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I'd guess that there are no solder points, there's a body with the rotor in it, riveted to the pcb, and that rotor has spring contacts that bear on pads directly printed on the board i.e. the board forms part of the assembly and it won't be any use by itself - just like the snap action switches on that board, they will bear down onto pads printed in the board itself.

enter image description here

Here's a transparent rotary switch that shows what is printed on the pcb that's part of this assembly. Typically these small encoders are quadrature encoders, so there's two traces with sectors offset from each other, and a center pad for the push action.

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As for repairing this board - check the connections at the end of the ribbon cable, looks like there are some corroded joints there.

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  • \$\begingroup\$ The connections are good, the press push switch at top of rotary encoder is bad from inside, I don't know how to bypass only SWITCH and make it function-able with other type of switches maybe Mini switch ? \$\endgroup\$ – Muhammad Sannan Khalid Jul 19 at 9:06
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    \$\begingroup\$ Most likely the encoder tracks have a common connection, there should be two of the traces that will go alternately shorted to it and then open as you turn the knob. The switch probably connects to the two remaining traces - I see five running under the body. If you can find an encoder like ttelectronics.com/TTElectronics/media/ProductFiles/Encoders/… available locally, you might be able to just cut a hole through the board and mount that, and add jumper wires to the traces - once the body is removed by grinding the rivet heads you'll see the right connections. \$\endgroup\$ – Phil G Jul 19 at 13:27
  • \$\begingroup\$ OK, I'll give it a try. Thanks for assisting. @phil G \$\endgroup\$ – Muhammad Sannan Khalid Jul 19 at 14:25
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It is a surface mount component. You can apply heat to the rear of the board behind the part with a heat gun to remove it.

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  • \$\begingroup\$ Unlikely. If it was surface mounted it wouldn't require the plastic rivots to be peened over on the underside to hold it in place as the solder would do the job. See PhilG's comment above. \$\endgroup\$ – Transistor Jul 18 at 17:06
  • \$\begingroup\$ @Transistor au contraire. Surface mount soldering is NOT suitable for mechanical security, especially a knob that is regularly twisted and pushed -- that's a recipe for a very short-lived product! They likely soldered the switch in place for the electrical connections, then riveted it to the board so mechanical stresses from daily use are taken up by the rivets instead of the solder joints. \$\endgroup\$ – Doktor J Jul 22 at 14:36
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The trace in the top right corner of the red circle could be broken. Maybe it's enough to fix the trace.

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  • \$\begingroup\$ Trace is good. I checked the continuity \$\endgroup\$ – Muhammad Sannan Khalid Jul 19 at 9:02

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