Makita 447M shopvac / dust extractor

[artag]

I picked up a faulty 110V (centre-tapped building site style) Makita shopvac at a local auction recently and could have saved some work if I'd been able to find some repair notes. I'm not going to strip it all down and do a video but I thought I'd just leave something here for google to find for someone else.

The vacuum cleaner is a pretty high end machine, selling for about £550 or half that secondhand. It's a 2.4kW unit with an M-class particulate filter and a fancy device for shaking dust off it. It can also sense the current taken by a tool and automatically switch on the vacuum when the tool is operated.

This unit was dead, with no motor power and no pass-through power.

As is usual with Makita, user manuals and an exploded parts diagram are easily available, as are the parts (though some are annoyingly large subassemblies). The first problem was getting it apart : the diagram shows a single long M6 bolt into the lowest part of the top handle - part 3 on the attached jpeg - and two screws in each of the clips - part 59 -  which hold the lid down. Removal of these, and the visible screws around the filter, left the cover still firmly retained.

Eventually I pulled hard on the handle, assuming it was somehow hooked into the other end  (nearer the switch panel). It isn't. It's fixed with another long socket-headed bolt whose head is hidden down a deep hole underneath the pleated filter.  I broke the retainer for its nut, which meant the handle came off but the cover was still held in place. It did at least reveal the presence of that bolt, and removing it freed the cover at last.

It's not actually necessary to remove the filter-shaking mechanism - parts 49-51 - but removing the semi-circular filter guard - part 52 - (4 obvious screws) makes it much easier to access that hidden bolt with a normal-length hex driver. A double-length hex driver (about 300mm) would be useful to avoid removing the guard.

Once inside it was fairly easy to find the problem.

The main rotary switch is a two-pole switch that disconnects both mains wires from the main motor and the 110V passthrough connection. It's important that both poles are switched as the power is actually 55-0-55 with an earthed centretap, so if only one side is switched there is still 55V above earth on the passthrough connector. I don't know how this translates to US 110V versions or 240V versions but the switching is probably the same.

One of the switch contacts (the one identified as Neutral, towards the back of the switch) was burnt,  making it impossible to pass any but a light current and that not reliably. The switch is a Makita special and doesn't seem to be sold separately (to be fair, it's not easy to remove) : the intended replacement is the whole control board at about £110-£140.

However, the switch has pins both into the board and spade terminals sticking up. Mains comes in on two of the spades and there is a spare spade which is an unused switched neutral. This presented a convenient hack : moving the incoming neutral onto the switched side bypasses the broken contact but still leaves the motor and passthrough output switched via the other contact.

For the reasons mentioned above this is an unsafe repair for the 110V centre-earth version. The motor and passthrough socket switch off but one of the passthrough pins is still at 55V above earth. I intend to make a safer repair (if I can't find a cheap switch replacement) by using the switched 110V to operate a contactor and switch both sides of the passthrough power with that. It may not be required on the 240V or 110V unbalanced versions.

If you know about the second bolt mentioned above, you shouldn't damage the handle as I did. New handles are available at a not unreasonable £25, but I was able to repair it invisibly by putting an M6 joiner where the hidden nut had been, and an M6 screw into that joiner from above (the handle, when removed, can be split in half, revealing the M6 nuts). This has made a strong repair, but best avoided!


Now I just need a hose, which didn't come with it. It seems to use about a 57mm pushfit connection, possibly tapered, and up to 38mm hose. A rotary control adjusts the cleaner for the hose size : not sure how, possibly only by adjusting the threshold of the blocked-hose sensor, possibly by limiting max vacuum. The official hose is fairly expensive at about £80, though there is a cloned one available at £40. A Numatic (Henry) hose is way cheaper .. it just needs an adapter. I haven't found one yet but it seems an ideal candidate for a 3d print - these are often made for the other end of the hose, to adapt it to the vacuum port on most woodworking tools.