The fan is making a lot of noise. How do I fix it? How does it come apart?

Bearings have gone in it... The fans are standard part. Take number off the label and search for the same unit. Note if it has two or three wires. If it has only two wires, replace with one of same voltage and current or wattage rating and of course that fits size-wise. Three wire ones have a sensor and you are best to replace with exact unit.

First thing: Make sure you are using balanced audio connections... XLR or TRS cables.

Next make sure ALL, and I do mean ALL interconnected equipment is powered from the same receptacle or source.

Ground loops by running mixer from a receptacle at one end of a room and speakers and amplifiers from the other is asking for not only noise, but possible damage due to ground bounce on the audio lines. Run an extension to the mixer if you are using a snake for example.

Bo, the fans cannot be lubricated. If the noise is from bearings, replacement is the only option.

You can either oil it up OR replace it for around 20$
Both ways involve removing the amp from the casing by unscrewing the 6 screws on top and sliding it out and then getting the fan out

locate the fan; locate the 4 outside screw covers that are next to the fan grill screws and pop them open. Remove the four screws that are under those plastic covers. The fan should separate. Take Fan out and remember how it was in there.
To oil: lift the sticker and locate the rubber plunger in the middle of the fan; remove it. Then, put ONE drop of regular 3-1oil NOT-wd-40, pb blaster or bike lube. re-assemble
To replace: just unplug old fan and then replace with new fan. I recommend replacing the fan when it gets to the point of bearing noise because oil doesn't always fix this.

Best thing is to open the unit and extract the fan and find the EXACT model number fan online and replace it. There are only two wires to solder., but mechanically these can be a mess to get to.

The hissing is caused by a bad connection, most likely at the cable jack. Try replacing it and while you're doing that check the rest of the components - especially the potentiometers, used ones generate a lot of static.

Try to remove the fan and look for the sticker on the back side where the wires come out.

Remove the sticker, underneath it there will be a small aluminium cap (sometimes there is no cap and the axis is readily visible when you remove the sticker).

Take the cap off with a sharp tool (it shouldn't require a lot of force to do it), now you should be able to see the fan axis being held in place by a small clamp - put a drop or two of machine oil in there, move the fan blades a little to make the oil flow past the axis into the bearing.

Reinstall the cap, put the sticker back in place, reinstall the fan and test it.

Sometimes this will make things better, but if it doesn't then it is only fair to replace the fan.

regards

Triarcuate

As it heats up it is heating the lubricant in the fan bearings which dries out and hardens over time. You can take the fan apart and clean the blades and relube the bearings but it is not easy. It may be easier to just replace it .

It might be giving notice, it might have some loose screws, but then again, it might just need some oiling.

There's probably a sticker on the rear side of the fan (where the power wires come out), remove it, underneath you'll see an aluminium cover near the center. Take this cover off with a pointed knife or similar, it should come off with just a slight force and you should now see the axis fixed in place by a clamp.

You just need to put a drop or so of oil, just make sure it reaches underneath the clamp into the bearing/bushing and if the bearing/bushing was just a bit dry or dirty and if it's not really damaged then the fan shoud now run quietly.

Put the aluminium cover and the sticker back in place, try it out, if it's silent, you win, if it's still giving notice then it should most probably be replaced.

regards

3rq8 (Triarcuate)

Could very well be the fan. The motors can cause interference. There may be a solution to get rid of the noise. Some copper shielding tape may help. You could rule out it being a microphonic preamp tube by turning the amp on as normal and tapping the tubes with something non-conductive. If you hear the tapping noise coming thru the speakers while doing this to a particular tube, replace it. With power tubes, the tops of them turn white on the top when they become microphonic, along with plenty background noise.