My First Watt M2 clone has been reliable (and great sounding) for two years since I built it. It recently blew a fuse (it looks like on startup). I replaced the fuse and tested with some sacrificial speakers. All was well, and it ran for a couple of weeks before blowing a fuse today. I guess the first question is, is it a bad idea to bump up the fuse values and see what happens? The current fuses are 2 amp 125v. Is that conservative? The next question is why might it blow fuses now when it didn't before? Which leads to the third question, should I start diagnosing instead of putting in higher value fuses?
Just use a slightly larger fuse, try 2.5A instead. Maybe your AC line is higher these days, or a thermistor has changed.
Hi, from the user's manual it says that amp draws 160W and fuse for 120VAC should be 2.5A.
I would measure the AC RMS current just to check if it is within the expected value - it should be around 160/120=1.3A.
https://www.firstwatt.com/wp-content/uploads/2023/08/prod_m2_man.pdf
"The initial setup of the amplifier is very straight-forward. Place the amplifier in a well-ventilated location, as it draws about 160 watts during operation and requires as much opportunity to cool itself as possible"
"Fuse 3AG slow blow type,
2.5 Amp for 100-120V
1.25 Amp for 220-240 V"
I would measure the AC RMS current just to check if it is within the expected value - it should be around 160/120=1.3A.
https://www.firstwatt.com/wp-content/uploads/2023/08/prod_m2_man.pdf
"The initial setup of the amplifier is very straight-forward. Place the amplifier in a well-ventilated location, as it draws about 160 watts during operation and requires as much opportunity to cool itself as possible"
"Fuse 3AG slow blow type,
2.5 Amp for 100-120V
1.25 Amp for 220-240 V"
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Often the inrush current can be sizeable on startup as whatever capacitors are filled. That’s generally why it’s a slow blow fuse and not a fast blow one, to allow for the extra startup current. Those fuses are dependent on temperature and have a tolerance too. I’ve had different brands blow in one brand and not in another at the same current. I agree with what others said, it shouldn’t be bad to bump it up slightly.