When buying an off-the-shelf computer I assume it gets tested to make sure for example that the power supply meets the regulation, the battery and usage does not exceed the limits etc.

How does it work when building or substantially customising a laptop/desktop, is it the case that the parts are approved individually and therefore the whole system is approved to be sold in the UK or is it completely not regulated?


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There are several 'regulations'.

The power supply bears the brunt of complying with many. Mains safety, mains-borne EMI, low power when in standby, power factor. The rest of the computer is at low voltage DC, so doesn't influence these.

Fire risk should be handled on a part by part basis, with them being fused internally or otherwise protected from drawing too much current, or being metal cased so that a burning component in a part doesn't spread to others.

Transmitted EMI should have also been pre tested part by part, but the connected system obviously cannot be tested for that until it's assembled. Here, the case, with its conductive flanges can improve the system EMI. I'll wager that custom-built computer suppliers don't test each machine they build for radiated EMI anyway, as it's a difficult and expensive test to do properly, but rely on the parts and case.


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