The "Quiet Mesa Walkabout" project...

[BillyB_from_LZ]

Reviving a long thread on a topic of interest so that relevant information can be found more easily by others in the future. Here are my questions, for those who have performed this surgery:

The solders on the board, where the resistor (which should be removed to maximize fan speed) is located, are somewhat buried in this amp. Not easy to access. How did you get to these solders? Did you detach the heat sink and flip it over and (hopefully) out of the way, at least within the limits of the wires connected to the heat sink?

Do either of these two solder joints on the board poke through the board? Particularly the resistor. Will it be necessary to get the soldering iron under the board, in order to release the resistor or the other wire? Or, alternatively, are these solder joints just 'surface' connections?

When I replaced the fan in my Walkabout years ago, I peeled the label on the fan back and unsoldered the wiring at the fan rather than at the circuit board.

 

[Old Fart]

In another thread, I had mentioned the factory fan and the SilenX both use 12 VDC and that the SilenX draws roughly half the current (0.09A compared to 0.2A). Agedhorse replied with another significant concern about how the SilenX might deal with different static pressures. It may be less able to move air into a box which has fewer vents and therefore might be more pressurized:

The fans are not terribly close. The SilentX is 32CFM and no static pressure value is listed which assumes it to be free air (no static pressure). One way to make a quiet fan is to give up the ability to load the fan down with acceptable air flow. The Sunon is about 40CFM with the air flow stalling at .20" H2O static pressure. There is no way to know how that SilentX fan will perform under the static pressure load that the amp places on the fan, and if the slope is different (it's almost certainly a shallower slope) the air flow will be lower as well. That's why without testing and knowing the most important spec when comparing fans for cooling performance, it can't be stated that the fan is adequate. There was one that was close enough, but I do not recall which one it was.

This is also why when changing a fan in an amp where the fan speed is proportionally controlled, it's even more important that the slopes and end points match closely. The servo driver circuit's gain is calculated based on the design temperature set point and end point so that as the amp heats up, the fan speeds up to cool the amp down. If the slope is wrong, it will affect the set point and also possible the end point (beyond which the amp's reliability is jeopardized). The Walkabout needs every bit of cooling available in the original fan, as there is significant static pressure drop (which is partly why the cooling system is as noisy as it is).

 

[Old Fart]

mikeswals seems to have a similar concern:

With the last version of the WA, the top lid has lots of vents. The OE fan was way louder in this case than in any previous non-vented lid version I had. To check I laid a panel covering the top just to listen, and I wouldn't have done the Silenx fan if it were just solid lid.

My Walkabout has vents on the two short sides. Do some Walkabouts have more than just the side vents? Some are more vented than others. is mine one of the better-vented ones, or not?

I also notice, with interest, that the Scout cabinet vents the air from those side-louvres downward, toward the rear of the head.....where the fan gets air. In other words, the Scout cabinet is configured so that the fan gets some air that has already been through the heat sink and is therefore warmer. Hmm....

 

[agedhorse]

I’m going from memory here, but the voltage MUST be measured at the SOURCE side of the fan dropping resistor to verify that it is 12V +/- 10%. It’s possible that some versions may have as much as 16-17V and the resistor is necessary to drop the voltage, otherwise the fan can be damaged.

The value of the resistor varies with the rated fan current, which is why I suggest replacing with the factory part or seek a qualified tech to do these measurements and calculations.

If the voltage is ~12V at the source end of the resistor, it’s possible for the resistor to be bypassed with a wire from the source end to the load end. If the PCB becomes damaged due to careless or unqualified work, all versions except possibly the last version are no longer available.

There are a lot of power supply components on that PCB so if it’s ruined, the amp will no longer be useable or (practically) repairable.

There were different versions over the 10+ years of production, I am not familiar with all possible versions. (disclaimer)

 

[Willicious]

My Walkabout has vents on the two short sides. Do some Walkabouts have more than just the side vents? Some are more vented than others. is mine one of the better-vented ones, or not?

The WB cover received additional venting for its later incarnations. I tried to get one of these from Mesa, for my first-gen WB, but was informed they have none left on their spare parts shelf. Here's an example from 2016:

 

[BillyB_from_LZ]

The WB cover received additional venting for its later incarnations. I tried to get one of these from Mesa, for my first-gen WB, but was informed they have none left on their spare parts shelf. Here's an example from 2016:

View attachment 4033753

I believe that was the cover that was employed when Mesa sought UL Listing (or another safety Certification). While it makes sense from a heat dissipation standpoint, I would be concerned about the ingress of "dripping" liquids or similar.

 

[WannaJazz]

Has anyone tried the fan sold by Mesa Boogie, in the Walkabout?

Fan, Sunon Ball Bearing

I am keenly aware of the admonitions proposed by Agedhorse, regarding changing to a quieter fan.

The price of the fan is worth the gamble, the $100.00 an hour shop fee, on a gamble, is more than I prefer to risk.

So, I thought I would ask for opinions/experiences with the Mesa Boogie replacement fan.

 

[sunbeast]

Has anyone tried the fan sold by Mesa Boogie, in the Walkabout?

Fan, Sunon Ball Bearing

I am keenly aware of the admonitions proposed by Agedhorse, regarding changing to a quieter fan.

The price of the fan is worth the gamble, the $100.00 an hour shop fee, on a gamble, is more than I prefer to risk.

So, I thought I would ask for opinions/experiences with the Mesa Boogie replacement fan.

I think this was just the original equipment (and of course mentions the Walkabout in the description). Having replaced the fan in my Walkabout I feel the noise is a result of the placement and airflow through the chassis more than the result of a particularly noisy unit used. The decrease in noise comes with a significant decrease in fan power as well, so it’s definitely a potential gamble using most of the quieter fans suggested here. It isn’t a difficult part to replace on your own though if you want to try

 

[agedhorse]

There were some different fans used from the beginning to the end of the production, most fans we have used in the past 10 years are ball bearing because of the increased reliability. The original fan is the best choice.