Stiletto Ace Fan upgrade

[JustPassingThrough]

Hello,

The fan on my Ace had become rather noisy as of late and sounded like a hand dryer in a public bathroom (issue 1). I was also picking up some clicking through the speaker (issue 2)

Issue 1: replace the noisy fan.

This is fairly easy.

Get a Noctua A6x25- Either PWM or FLX. It does not matter. The PWM is the fancy version for computer case fans that has different speed levels and automatic speeds when temps get a certain threshold. That doesn't matter here.

You need to worry about 2 of the wires: YELLOW and BLACK. The other 2 are superfluous (I clipped them short and wrapped them in tape) and are used for the controlling/automated stuff mentioned above.

YELLOW = HOT
BLACK = GROUND

Strip these 2 wires back, leaving about 10mm of bare wire.

Unscrew the existing fan from the chassis. Desolder or clip the red and black wires from the fan and keep them as long as you're able. Too long a wire is infinitely better than too short in this case.

Splice the red and black wires to the yellow and black on the fan. I put the old and new side by side, twisted them together tightly, soldered them, then wrapped them in heat shrink.

Connect the wires like this:

STOCK / NOCTUA

RED to YELLOW
BLACK to BLACK

Heatshrink over your joins to prevent any future weirdness.

RESULT = Better cooling, fan is silent.

ISSUE 2: Fan noise coming through speaker.

According to Mesa the capacitor designed to quieten the power rail for the fan can die over time (it takes several years but is a known point of failure), go crappy, and short out. It's a 15uf/25v tantalum cap that you need to replace. I used a 22uf/50v electrolytic as I had them to hand. More filtering never hurt anybody.

This cap lives in parallel to R17, and is located here by the big tall capacitors. See the red circle. It's that yellow bullet shaped cap to the right hand side of the tall guy. The chamfer (facing the pots) is the positive end. Do not switch the polarity. Unsolder it, then solder the new cap to the same place, over the resistor. This will quieten the power supply to the fan and won't fail as readily as tantalum.

RESULT: No more clicking, quieter fan operation. All is good.

Total time for the mod is about 30 minutes front to back, and 25 of that is getting the chassis out and then back in again. There's really not a lot to it for a really useful upgrade to a quality part that's cheaper and better than the fans Mesa sells and will last years, they even come with a 6 year warranty.

Cheers.

 

[rarebitusa]

Nice writeup, thanks for posting those details.

My Ace fan went south as well. I replaced it with a noisy cheap fan and integrated a toggle off/on switch inline. Not a good move on my part, so I welcome the Noctua A6x25 recommendation.

Was unaware of the fan noise coupling, but I have moved the Ace chassis to a headshell maybe that is why I don't notice? Or else my ears are blown, which is very possible.

 

[JustPassingThrough]

Nice writeup, thanks for posting those details.

My Ace fan went south as well. I replaced it with a noisy cheap fan and integrated a toggle off/on switch inline. Not a good move on my part, so I welcome the Noctua A6x25 recommendation.

Was unaware of the fan noise coupling, but I have moved the Ace chassis to a headshell maybe that is why I don't notice? Or else my ears are blown, which is very possible.

In my case there was a ticking noise through the speaker occasionally, that would stop if I jammed a pencil into the fan, then start again once the fan started. Mesa suggested that 15uf cap was shorting out causing the interference.

Plus if you've ever tried to record the combo with the fan, the stock one being so loud gets in the way of that.

But without the fan doesn't the amp overheat? There's no vent above the tubes like on other amps.

 

[tbonesullivan]

The combo is VERY close quarters due to it being closed back, so the tubes have very little room to radiate heat. The fan is definitely needed, but yes, it can be somewhat loud. The fans MESA uses are chosen for reliability and air flow, not for noise unfortunately. I have found however that the dust many people let build up on the fan often is part of the reason they are so loud.

 

[JustPassingThrough]

The combo is VERY close quarters due to it being closed back, so the tubes have very little room to radiate heat. The fan is definitely needed, but yes, it can be somewhat loud. The fans MESA uses are chosen for reliability and air flow, not for noise unfortunately. I have found however that the dust many people let build up on the fan often is part of the reason they are so loud.

I cleaned mine off with compressed air, it was still noisy. They're just cheap fans that don't have very good air flow and aren't really that reliable compared to what else is out there for around the same price. Noctua are the Rolls Royce of fans and you can find them cheaper than Mesa will sell you one of their off brand ones.

Luckily it's an easy change if it bothers the end user. If it doesn't, it doesn't, that's cool too.

 

[rarebitusa]

The combo is VERY close quarters due to it being closed back, so the tubes have very little room to radiate heat. The fan is definitely needed, but yes, it can be somewhat loud. The fans MESA uses are chosen for reliability and air flow, not for noise unfortunately. I have found however that the dust many people let build up on the fan often is part of the reason they are so loud.

Yea those tubes are right on top of that closed back aren't they. Kinda one of the reasons I moved the Ace chassis to a headshell. BTW the Ace combo cab makes for nice 1x12 extension cab.

 

[tbonesullivan]

Yea those tubes are right on top of that closed back aren't they. Kinda one of the reasons I moved the Ace chassis to a headshell. BTW the Ace combo cab makes for nice 1x12 extension cab.

YEP. Having to pull the chassis to do ANYTHING with the tubes is kinda annoying. But things are like that with other amps I own, like a Rivera Stage IV, which has that HUGE EM12 speaker in it, which gets in the way of two preamp tube shields.

 

[JustPassingThrough]

Do you though? To change power tubes you just take the back off and there right there.

Preamp tubes sure, there's the fan in the way but as far as amps go it's a relatively easy chassis to get in and out. My dual rec is a pain in the ass.