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· Premium Member
422 Posts
Firstly, very best wishes to everyone for 2021.

This months Chip Pan Fire has resulted in the destruction of the P mosfet and a ferrite filter-bead on a C2817 decoder.

The past two monthly outrages included wrecking a microcontroller, and an NO2 mosfet respectively. Thanks to the considerable patience of experts here I was able to replace and repair both chips - and learn a great deal in the meantime.

I have already sorted out the P mosfet, but now need to ascertain the specification of the decoders ferrite filter-bead to order a replacement. My research tells me that this involves identifying the physical size, impedance and frequency for this component; but there maybe more.

1) Does anyone have this info. please?

2) Also, is it possible to measure a working ferrite filter, in or out of circuit, to obtain the correct values for a reorder?

Thank you.


· Banned
6,404 Posts
Hi Keith,

Sorry I havent ever needed to replace a FB on a standard Scalextric chip.

In terms of key parameters we are looking for low DC resistance and high current drive... then as much inductance as can fit inside a 0805 or 0806 smd footprint.

I think the rs part 7241542 should be fine:

1/ 20mOhms and 3.5A
2/ impedance of 60 Ohms at 100MHz
3/ 0805 footprint i.e. 2mm x 1.2mm

Warning - I never tried this myself. Others more into decoder repairs may have better ideas/advice...

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