paul_5 Posted March 13, 2017 Share Posted March 13, 2017 I was always taught that fuse rating was Watts / Volts x 1.25 I've got an Ampeg pre (finally) that states 15W Max, so at 230V the sums come out at 0.0815. What size fuse should I put in the IEC (kettle) lead? Quote Link to comment Share on other sites More sharing options...
T-Bay Posted March 13, 2017 Share Posted March 13, 2017 Does it have an internal fuse? Most amps do and they tend to be in the range of 1-5 amps (most are 1-3A it seems from when I wa searching when I had a problem with mine). If you can find the rating of that one put the next available size up in the main plug. Quote Link to comment Share on other sites More sharing options...
paul_5 Posted March 13, 2017 Author Share Posted March 13, 2017 Thanks for the tip, it's got 2 internal fuses on the schematic (one for 230V, one for 115V) rated at 1/16 A SB (presumably slow blow) - 0.0625A I'm thinking that even a 1A in the plug will be pointless. Quote Link to comment Share on other sites More sharing options...
T-Bay Posted March 13, 2017 Share Posted March 13, 2017 Generally they are as the amp one will go first if needed. I guess it protects against a damaged lead touching something you don't want it to. Quote Link to comment Share on other sites More sharing options...
paul_5 Posted March 13, 2017 Author Share Posted March 13, 2017 I could try a 100mA one and see what happens. Quote Link to comment Share on other sites More sharing options...
Downdown Posted March 13, 2017 Share Posted March 13, 2017 [quote name='paul_5' timestamp='1489438022' post='3256974'] I was always taught that fuse rating was Watts / Volts x 1.25 I've got an Ampeg pre (finally) that states 15W Max, so at 230V the sums come out at 0.0815. What size fuse should I put in the IEC (kettle) lead? [/quote] 3 amp. Because the Ampeg has been designed to accept an IEC mains connector, it follows that in most countries the mains lead will not have any fuse in it at all. Knowing this, the Ampeg designers will have designed some form of over-current protection within the device itself, usually an internal fuse, sometimes a fuse holder mounted on the rear panel near the IEC mains input. In the UK, mains plugs are fitted with fuses and an IEC mains lead can be treated as a 'device' in its own right because it can be used for many different appliances. Thus, the fuse in a UK-plugged IEC mains only has to provide over-current protection for the mains lead itself. So far, so simple. Things are slightly complicated by the fact that the IEC connector is rated at 10A and the leads themselves quite often have 0.75mm2 wires that are rated at 6A. In such cases, a 5A fuse is fine. However, BS-something or other (I forget the number) only recognises 3A and 13A fuses and generally recommend 3A for any appliance less than 700W and 13A for anything over 700W. Quote Link to comment Share on other sites More sharing options...
paul_5 Posted March 13, 2017 Author Share Posted March 13, 2017 Cheers Downdown. That makes more sense. Quote Link to comment Share on other sites More sharing options...
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