2
\$\begingroup\$

The base of my my beloved robotic lawn mower has stopped working. It is the base that is the problem. If I unplug it for a while, then it will work for a few minutes, when I reconnect it.

I have deduced that the error fault is on the control board, and since it is four years old, hand has been outside in all weather - frost and sunshine, I am guessing the capacitators may have lived out their lives.

But I am not sure how to decode the values on these "modern" SMD capacitors.

Any experienced folk in here, that can help me translate the values of these "t4 22H C M", "100 HFT 6G7", "6O 330 jzJ" and "100 VFK. Q86"?

enter image description here

\$\endgroup\$
4
  • 2
    \$\begingroup\$ Just to be sure you use the right voltage rated capacitor, use your multimeter to check the voltage across those capacitors while the device is working before you change them, to be sure what is the higher voltage that each of them reaches. \$\endgroup\$
    – Christianidis Vasilis
    Commented May 2, 2022 at 8:42
  • 2
    \$\begingroup\$ 330 = 330 uF, 22 = 22 uF and so on for these types. Usually one of the letters denotes the voltage rating. I have not found a consistent translation for them among different manufacturers so you need to find the datasheet to be sure. When in doubt, go for higher voltage rating and same capacity if you are replacing them. \$\endgroup\$
    – winny
    Commented May 2, 2022 at 8:59
  • \$\begingroup\$ @ChristianidisVasileios Ah - great tip, hadn't even thought of that. My greatest concern was indeed how I ensured that i bought capacitors with high enough voltage rating. Of course I can just measure. Thank you very much. \$\endgroup\$
    – Wispheren
    Commented May 2, 2022 at 9:09
  • \$\begingroup\$ @winny I thought as much, but would like confirmation. Thank you for your answer. \$\endgroup\$
    – Wispheren
    Commented May 2, 2022 at 9:10

1 Answer 1

Reset to default
4
\$\begingroup\$

FK capacitors from Panasonic are 105°C low-ESR types. Do not replace with high-ESR general purpose caps, it will not work. You can replace with the same caps, they're easy to find and not expensive.

enter image description here

Same for the other Panasonic FT capacitor.

I have no idea what the other two are, probably general purpose. In case they're low ESR models too, you can replace with FK series.

However I would doubt that this board is the source of your problems. If the device has cooked in full sunlight, I'd first investigate the power supply and other parts that dissipate a lot of heat. These will get even hotter in sunlight. If the power supply is a simple model with a single voltage output, perhaps you can test the device with an equivalent known-good power supply to get a quick answer.

Another source of these intermittent problems can be a bad connection or cracked solder joint. Due to thermal dilatation of materials, sometimes it makes contact, then the device heats up, and it no longer makes contact. Then you let it cool down and it makes contact again.

\$\endgroup\$
2
  • \$\begingroup\$ Thank you very much! Initially I agreed with you, I seriously doubted that the board was the problem. However I have made new fresh connections, and measured the total resistance to be around 4 Ohms on the board (which is quite alright for a few hundred meters of wire). And with regards to the power supply, my brother has an identical robotic mower, and with his power supply, the problem is exactly the same. The board is the "last suspect". And while it is powered, a distinct switch mode psu clicking sound is emitted. So that is why I suspect the capacitors. \$\endgroup\$
    – Wispheren
    Commented May 3, 2022 at 8:29
  • \$\begingroup\$ Oh, okay! That sounds legit. You can check the power supply rails at the output of the switching regulators on this board too, with a scope or a multimeter. Maybe one of the buck diodes is shorted. Also check these power rails for short to ground with ohmmeter. Could be a cracked/shorted ceramic cap. \$\endgroup\$
    – bobflux
    Commented May 3, 2022 at 8:38

Not the answer you're looking for? Browse other questions tagged or ask your own question.