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I have a problem with identifying an SMD component that I'm sure is burned and has to be replaced.

It should be a transistor used to switch the 24 V coil of a J01A-24-F relay.

Input at the supposed base pin (it could also be a MOSFET, so the gate) is 0/5 V coming from a PIC18F452. The coil is inserted on the collector side. The emitter is at ground. I noticed that there are no resistors to polarize the transistor, so I suppose the resistors, if any, are internal to the component.

The board controls a gas boiler. The relay opens/closes a water pump on the 230 V side.

Over the component I read "XF" horizontally and "5N" vertically. I thought it could be a transistor like the RN1101F but I'm not sure. Could you please suggest the correct code or an equivalent, (preferably not an SMD to facilitate soldering and purchase)?

I attached a photo.

enter image description here

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  • \$\begingroup\$ TR = transistor? \$\endgroup\$
    – JRE
    Sep 15, 2022 at 13:03
  • \$\begingroup\$ Yes, I edit the post. \$\endgroup\$
    – daigs
    Sep 15, 2022 at 15:21

1 Answer 1

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RN1106 is a plausible choice. If you can remove a similar one and measure the E-B resistance you'll have a much better idea if it's an exact replacement (should be ~52kΩ in one direction and perhaps lower in the other).

If you want to go with non-SMT you could hack in a 2N4401 with a couple resistors (such as series 4.7k and 47k E-B), but make sure you don't compromise safety in any way.

schematic

simulate this circuit – Schematic created using CircuitLab

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