hankhill Posted March 31, 2022 Share Posted March 31, 2022 (edited) In a quest to build a lightweight rig to save my ageing back I’ve just bought a (used) Peavey Minimax 500. So far it’s great apart from the loud fan noise, which reviews had led me to expect. It seems to be a standard 50mm fan, and there are several so called silent 50mm fans around online so I’m going to try one. I also have an inline 12v fan potentiometer from a PC that I built, which would slow the fan down. Or, maybe I can fit a thermal switch so it’s not constantly running? The noise will be less of an issue onstage but is too loud when playing at home. Has anyone ever done a fan swap or thermal switch mod on this or similar amps, to reduce the fan noise? Did it work? TIA Edited March 31, 2022 by hankhill Quote Link to comment Share on other sites More sharing options...
Mottlefeeder Posted March 31, 2022 Share Posted March 31, 2022 If it is a 12v fan, this circuit will make it temperature controlled. David https://sound-au.com/project42.htm 1 Quote Link to comment Share on other sites More sharing options...
hankhill Posted March 31, 2022 Author Share Posted March 31, 2022 So, now that I have opended up the amp, I have discovered that the fan is 24v not 12v, and there is very limited clearance between the outer wall and the circuit board, which means a (more common) 25mm depth fan almost certainly won't fit. The current fan is 15mm deep. So I'm now searching t'internet for a 60x60mm fan, 20mm deep, and 24v. My theory is that a deeper fan (20mm instead of 15mm) will be more efficient and therefore won't need to spin as fast. The current fan just screams at full speed all the time, I've not been able to find the specs online, so I've no idea of the rpm its doing, its just a cheapo generic chinese OEM fan. My current Ashdown RM500 also has a fairly noisy fan, I assume that manufacturers just choose the cheapest they can find. Quote Link to comment Share on other sites More sharing options...
John Cribbin Posted March 31, 2022 Share Posted March 31, 2022 If you are happy to solder, you could look at reducing the 24 volt feed to the fan with a couple of resistors. Look up voltage dropping resistors to give you an idea of what's involved. It's been decades since I played with that stuff and the details are hazy ... Quote Link to comment Share on other sites More sharing options...
nekomatic Posted April 1, 2022 Share Posted April 1, 2022 16 hours ago, Mottlefeeder said: If it is a 12v fan, this circuit will make it temperature controlled. David https://sound-au.com/project42.htm I don’t see why that circuit wouldn’t work off 24 V for a 24 V fan. Bump up R5 to 750 ohms ish, and maybe R6 and R7 to 2k each. Quote Link to comment Share on other sites More sharing options...
fleabag Posted April 6, 2022 Share Posted April 6, 2022 (edited) Be careful when buying your chosen fan. Many sellers on say Amazon, dont publish the db levels. Some of the very quiet fans are down to 12Ddb. If you can find any at 25 db, or lower, they'd be fine. The sound of a person breathing at 1 metre in a quiet room, no other noise, is about 25db, as long as they're not asthmatic. I think 24v 60x60x20 and quiet, might be tricky to find. Edited April 6, 2022 by fleabag Quote Link to comment Share on other sites More sharing options...
hankhill Posted April 6, 2022 Author Share Posted April 6, 2022 (edited) I have literally just finished putting my Peavey Minimax amp back together having found, after a long search, a suitable fan. I had to go for a 25mm deep fan in the end and chamfer the bottom edge to clear the main PCB. It is supposedly rated at 27db. Sadly, having just fired it up, I don’t think it’s made any difference to the noise. All the ultra quiet fans are 12v as they're for PC use, but the Peavey fan is 24v. I see that its set blowing into the amp, and there are vent holes on the other side where you can feel a draught exiting the amp. Would turning the fan around make a difference? Or am I taking too big a risk? Maybe next I’ll look at fitting a fan controller somewhere, so I can turn it down when rehearsing at home. Or, a thermal switch but that’s beyond my skills and I wouldn’t know where to place the sensor. Edited April 6, 2022 by hankhill Quote Link to comment Share on other sites More sharing options...
BigRedX Posted April 6, 2022 Share Posted April 6, 2022 The other you need to check is that the flow rate of your replacement fan is at least equal if not greater than the one you are replacing. Some low-noise fans are low noise because they simply don't move as much air at the same rate. If you don't move a sufficient volume of "cool" air over the hot components at the required rate, they won't cool down enough and will eventually go pop... Quote Link to comment Share on other sites More sharing options...
hankhill Posted April 6, 2022 Author Share Posted April 6, 2022 Yes I was aware of flow rate and you’re right, silence comes at a price. Unfortunately the original fan label model number didn’t reveal any info via Google apart from 24v and 0.11A. I made sure the new fan was at least that power rating (it’s actually 0.12A). I think I will just have to accept that a noisy fan is the price to pay for a powerful yet light and compact amp like the Minimax. Quote Link to comment Share on other sites More sharing options...
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