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MarkBass combo fan noise

#23
Phaidrus said:
You're welcome. Let me note that in the case of the LM3 head it wasn't exactly plug and play easy. I had to remove the entire pcb board from the chassis in order to remove the fan, which meant cutting a number of zip ties that kept a bunch of wires tidy together, and then the fan plugs where not identical given that the replacement SilenX fan has a different plug to accommodate a third wire (don't know what it is for, perhaps @agedhorse could chime in and enlighten us). The stock fan only has two wires, black and red. So some soldering was necessary. So, as noted above, I don't plan to repeat this upgrade with another amp.
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There are 4 different configurations for that fan, some are compatible, some are not, it depends which one. The third wire may be tach feedback or PWM control. Best to use the correct factory fan.
 
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#26
BadMonk said:
The Sanyo fan isn't plug and play either but not as bad as pulling the board. MB uses a fan to board connector in my LM 250 head, making it a bit of a pain. I'll not spend money on a OEM fan. After just eight months, fan blades pull away from the fan housing by a quarter inch. Junk.
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Or you just got a bad one, or it got broken by someone monkeying with it.
 
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#34
Digging up this thread because I recently took delivery of two new MB58R CMD combos (with the Little Mark 58R head), both of which had significant fan noise. Fine for playing with a band, but a dealbreaker for the practice room or studio use.

I opened one of them up intending to see whether the fan would be replaceable and noticed the fan is only loosely secured to the chassis with some sticky foam. After experimenting with putting some finger pressure on the fan I figured it's the looseness that's causing the fan to rattle a little.

So I cut up some thin layers of extra foam (packing material for some headphones I bought) and placed them at the points where the fan makes contact with the chassis and the lid. These hold the fan more firmly in place and provide a bit of isolation.

The fan noise is vastly improved. Almost inaudible when the amp is cold and quite acceptable after it warms up.

IMG_3084.jpeg

IMG_3086.jpeg
 
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#35
PatTheDog said:
Digging up this thread because I recently took delivery of two new MB58R CMD combos (with the Little Mark 58R head), both of which had significant fan noise. Fine for playing with a band, but a dealbreaker for the practice room or studio use.

I opened one of them up intending to see whether the fan would be replaceable and noticed the fan is only loosely secured to the chassis with some sticky foam. After experimenting with putting some finger pressure on the fan I figured it's the looseness that's causing the fan to rattle a little.

So I cut up some thin layers of extra foam (packing material for some headphones I bought) and placed them at the points where the fan makes contact with the chassis and the lid. These hold the fan more firmly in place and provide a bit of isolation.

The fan noise is vastly improved. Almost inaudible when the amp is cold and quite acceptable after it warms up.

View attachment 7355064
View attachment 7355065
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Good job! You can also buy a special rubber gasket for pretty much any size fan and mount it between the fan and the chassis. And there's even rubber "screws" to use instead of the metal ones for even more isolation/noise/vibration reduction.
 
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#37
PatTheDog said:
Update: even after adding the extra foam, the noise was still a bit much so I replaced the fan with a Noctua NF-A6x25 FLX. Now it really is quiet!
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Hope there's adequate airflow, my experience is that the air flow suffers from these products (that's a big part of why they are quieter). If the airflow is inadequate, you run the risk of damaging the amp, but as long as you are willing to accept this risk it's your choice.
 
#39
PatTheDog said:
Good point. The air flow does appear to be a bit lower according to the specs 29.2 m³/h compared to the stock 34.3m3/h.
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It's not just the air flow number but also the static pressure the fan is specified at and the static pressure that the fan is operating at.

All of this factors into the actual air flow, and if a specific air velocity and SP is required in order induce turbulence in a portion of the circuitry that is a critical path in the cooling (there are many different areas of some circuits that require cooling), and it's inadequate, the real cooling fan fall off exponentially.

For example, on a class D design I worked on maybe 20 years ago, there were several different elements of a circuit that needed different degrees of cooling in order to function reliably. There were thermal protection sensors that protected high thermal loads by sensing the temperature of PCB copper traces adjacent to the components generating the heat. It was in this case critical to cool the component and not the sensor itself in order to maintain the necessary level of circuit protection. We received a patent on this approach that was later assigned to Fender for use on their products (presumably the class D Rumbles and Bassmans).
 
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