Tdw Posted August 20, 2010 Share Posted August 20, 2010 Hi , i have a trace elliot gp7sm ah300 head that destroys amp fuses very regularly. They never blow when the amp is switched on and working but rather when powering up or down (while the mute switch is off ) its hard for me to say if its on power up or power down or both. I have tried various fuses in the plug and it doesnt seem to make any difference. Just to clarify the amp fuses are 3.15 amp 250 volt glass fuses, the ones im using are fast blow. Sometimes it may go a week or more before blowing a fuse, at other times two may blow consecutively. Also the mute switch is somewhat crackely when pressed although i dont know if this has any relation to the fuses blowing. Any suggestions on what might be causing this and what could be done about it? Quote Link to comment Share on other sites More sharing options...
Moos3h Posted August 20, 2010 Share Posted August 20, 2010 [quote name='Tdw' post='931238' date='Aug 20 2010, 06:53 PM']Hi , i have a trace elliot gp7sm ah300 head that destroys amp fuses very regularly. They never blow when the amp is switched on and working but rather when powering up or down (while the mute switch is off ) its hard for me to say if its on power up or power down or both. I have tried various fuses in the plug and it doesnt seem to make any difference. Just to clarify the amp fuses are 3.15 amp 250 volt glass fuses, the ones im using are fast blow. Sometimes it may go a week or more before blowing a fuse, at other times two may blow consecutively. Also the mute switch is somewhat crackely when pressed although i dont know if this has any relation to the fuses blowing. Any suggestions on what might be causing this and what could be done about it?[/quote] You should be using Slo-blo ('T' rated fuses) - T means time-delay. There are massive current surges when powering on amps, and Fast fuses will just pop. Quote Link to comment Share on other sites More sharing options...
DHA Posted August 21, 2010 Share Posted August 21, 2010 [quote name='Tdw' post='931238' date='Aug 20 2010, 06:53 PM']Hi , i have a trace elliot gp7sm ah300 head that destroys amp fuses very regularly. They never blow when the amp is switched on and working but rather when powering up or down (while the mute switch is off ) its hard for me to say if its on power up or power down or both. I have tried various fuses in the plug and it doesnt seem to make any difference. Just to clarify the amp fuses are 3.15 amp 250 volt glass fuses, the ones im using are fast blow. Sometimes it may go a week or more before blowing a fuse, at other times two may blow consecutively. Also the mute switch is somewhat crackely when pressed although i dont know if this has any relation to the fuses blowing. Any suggestions on what might be causing this and what could be done about it?[/quote] The fuse in the mains plug is there only to protect the mains cable. Is it a kettle plug type? if so try another fitted with a 5A fuse. If the mains cable is 5 or 13A then you can just fit a 5A in the existing plug. It's a common issue with all amps as there is a large inrush current at switch on which is way above the normal operating current. Quote Link to comment Share on other sites More sharing options...
Tdw Posted August 24, 2010 Author Share Posted August 24, 2010 Thanks alot to moos3h and DHA for the replys , i have checked the plug and it appears to to be 5 amp cable with a 5 amp fuse, i tried another 5 amp cable/fuse and it didnt seem to make a difference, fuse still blew. I have ordered some slow blow fuses and i think this seems likely to be the issue. Quote Link to comment Share on other sites More sharing options...
Tdw Posted September 20, 2010 Author Share Posted September 20, 2010 Yeah the time delay fuses have solved it. I must have not been able to get the correct type and ended up with fastblow, then forgot. Thanks for the help guys. Quote Link to comment Share on other sites More sharing options...
flyfisher Posted September 20, 2010 Share Posted September 20, 2010 A fuse is deliberately designed to be a weak link in a power chain that will blow when too much current (according to the system design) flows. There are usually many fuses in any power chain. In this case, the 3.15A fuse in the amp, the 5A fuse in the plug, the 30A fuse in the consumer unit feeding the power circuit, the 60/100A fuse in the electricity meter, the ???A fuse in the local sub-station . . . etc etc. As the current consumption increases it's fairly obvious that the lowest rating fuse will be the one to blow first. Thus, with a 3.15A fuse in the amp, it doesn't really matter whether the plug fuse is 5A or 13A. It will have no effect on the amp fuse. The previous point about power-on current surges is the real issue, hence the need for a slow-blow fuse in the amp. Quote Link to comment Share on other sites More sharing options...
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