Fan in the bottom of a Peavey amp

[Novo]

this us for Enzo and anyone else who has old school peavey gear. Is there an amp with maybe a 400bh back that had a fan in the bottom? Would love a picture. Thinking of doing the same thing on a project.

Thanks,

Novo

[J M Fahey]

Whether there was one or not, you can build your own.
The only problem is getting 12 or 24V DC for the fan.

What voltages do you have available?

[Enzo]

Well why bother tapping the circuit when he can just mount a 120vAC fan and tap the mains wiring.

Most 400BH boards I see are in box-style heads, on the rear panel, and I don't recall ever seeing a fan in one. Generally the heat sink radiates outside the amp anyway and unless there is a bias problem, the amp board should run cool enough as is.

One important fact for fans is, they need a complete "circuit" for the air. You can't just make a hole in the bottom of the box and stick a fan there. There would also have to be an exit (or entrance, depending which way you have the fan blowing) vent so the air has a path. Otherwise, all the fan does is pressurize the box. You could mount a fan in the bottom over a hole, and vent the top, or vent out each end. or fan in one end and vent in the other.

There were powered mixers with fans, but I don't recall those using like a 400BH, seems to me those would be more like the innards of a CS400 or something. Box mixers like the ever popular XR600 had no fan.

[Paleo Pete]

I have an 80's Peavey MX, this amp

Peavey VTX MX 1 2 Stack Guitar Amplifier | eBay

It has a fan mounted in front, behind the Peavey logo, you can barely see it if you look close. I don't have that 4x12 cab, sure wish I did...love the road case though. It has a metal grille on back for plenty air circulation, it's not loud but for recording I have to unplug it. The plug is on top of the chassis, along with reverb tank plug, easy to reach after you remove the rear grille. Onstage I never notice the fan at all, even standing a foot away. Inside for bedroom practice I can hear it, but even at the lowest playing volume possible, play a note and the fan noise disappears.

One thing I found a while back about this same topic, you might consider using a 24 volt fan at 12 volts to reduce noise since it should work at lower RPM.

Enzo is right about the air path, same as with computers, fans are useless unless you have a definite path for air to flow through, other wise you're just pressurizing it. I've run the MX for recording for up to 6 hours without the fan plugged in, never noticed any heat problems. I do like having it, don't have to worry about playing outside on a hot day or whatever, but it seems to work fine without it. Unplug the fan, let it idle for an hour, I can still hold my hand on the chassis all day...without touching the tubes of course...that takes oven mitts...But all the electronics are still under the chassis, it only cools the tubes.

The only downside I noticed is that the fan sucks dust into the front grille, and it has a big dust colored circle there now after 20 years of using it. About 5 inch diameter I think...I don't know what voltage they used, I looked about 15 years ago and I think I've slept a time or two since then...

[Enzo]

Fans of all voltages have specs. Aside from size and voltage, they also are rated for air flow and noise. There are low noise fans.

[Jiji]

for the sake of discussion:
in the computer world you want a big fan with slow RPM for moving air in/out of an enclosure. quiet and reliable this way.
if you want to cool a heat-sink, say something that gets hot fast but it also has idle times, like a video card, you want a high RPM fan for the pressure it can create fast.
those are usually controlled by a temperature sensor. low energy but noisy on full RPM.

ball bearing ones last longer and are quieter. the ones without bearings last long and are quiet.
computer fans are 12VDC (1W-5W), brushless and are cheap these days.
I have seen very old computer fans still working -under a blanket of dust.