alright, i havent been here for a long time, but after some months of playing regularly in the practice room i brought my rack back home again and IMMEDIATELY got fed up with the mesa 20/20 4cm fan noise again. really, its aweful!
aanyway, i started to google again and all i found about annoying fan noise were basically my own complaints in a german boogie forum and here, so i decided that something finally had to happen.
obviously, the small 4cm fan is supposed to drag air through the transformators over the capacitors to finally ease the heat from the tubes via small air vents at the backside of the case. i had basically 4 options:
1.) let the small fan run at low speeds
2.) buy a replacement 4x4cm fan which is hopefully more silent
3.) switch it off completely and put 2 12x12cm fans at the backside of my 3HE rack
4.) find another solution
i tried 1.) first, but it seemed to run too hot when built into the rack, i didnt believe in 2.) since a small fan at high RPMs will always be annoying and audible, so basically i was left with 3.) or something else. i wasnt sure about 2 12cm fans at the back of my rack - it wouldve helped the tubes of the triaxis as well, but i wasnt sure about the cooling of the transformators in the 20/20, so i finally decided to go for 4.). in my case i found a reasonable spot for an 8x8cm fan in the 20/20 casing, drilled a big whole for it, checked for silent fans from the pc market which were guaranteed to run at the 5V power supply of the original fan. this is only possible, since the power amp was always the lowest of my 3 rack units and my rack leaves around 1cm space underneath the 20/20 - enough air for the fan. stuffed it all together and what can i say: wow, finally i like this damn noisy unit!
the be quiet USC 8x8cm fan is really absolutely inaudible at the 5V supply. the cooling is somewhat weaker than the cooling of the high RPM original fan, but strong enough to give me a comfortable feeling about the whole thing - eventually higher voltage can be found somewhere in the 20/20 (im no real expert in electronics, i just checked power demands of the fans and used the old supply cables for the new fan). the flow principle is somewhat diffrent now, since air is sucked in from the lower side of the case, pushed out at the sides/front and the original 4x4cm fan whole into the backmost parts of the case. overall the stream into the backmost parts of the case is weaker than with the weirdly placed original fan, but i think its working out fairly well. the unit is cold in the first part of the case, its handwarm in the middle section and it becomes hot where the tubes are. overall not much diffrent from the original setup.
made some pictures, hope you like it.