Thread: Makita HP1500 drill sparking
31st May 2008, 02:41 PM #1
Makita HP1500 drill sparking
My Makita hammer drill is sparking pretty badly internally and losing power.
Is this and indication that the bushes need replacing? If so, is it a simple enough job to do myself and are they easy to get?
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31st May 2008, 03:24 PM #2
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31st May 2008, 06:36 PM #3
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1st Jun 2008, 04:19 AM #4
as far as i know, the HP 1500 has no auto switch-off brushes. These would have built-in spring-loaded pads, which break free as a safety measure when the brushes start to wear beyond a certain minimum. The pads slide on the running commutator without scratching them until the armature stops and the springs behind the pads lift the brush carbons a bit from the commutator copper and stop the flow of electricity. The tool cannot damage itself any further and won't run until a brush change.
Without switch-off brushes, the worn bits of carbon are pushed out of their holders too far and can have their proper contact with the commutator sabotaged by bits breaking off or being wrenched in an odd angle. When the carbon is gone entirely, the pressure spring behind it remains pressing on the commutator copper and violently scratches the running strips. But by then, you will have seen spectacular fireworks and heard very odd sharp noises.
My advise would be to not use the drill for one second anymore before having inspected the commutator itself. Under good lighting, you can see enough of it through the air louvres above the hind grip, or to see it better still, you can screw loose one half of the housing (all parts lay loose then like in a Meccano box, so be careful that nothing drops out and is still in the same order when the housing halves are shut again; you need to have some experience to do this). Rotate the armature slowly by hand (by means of the chuck when the drill is in one piece, by means of the fan when the bottom half plus contents lies opened on the table) and inspect every copper commutator strip. There is the obvious slightly blackened track where the brushes touch the commutator drum, and this blackness as well as a certain smoothness, should be the same all around on all strips. There may an intermittent and ever so slight burning of one edge of every second strip, that is normal. When one or more strips however, show more burning-in than the rest, or show more blackening (darker, matt black) or even some signs from melting caused by arcing of violent spraks, than this will be a sign of one or more partly shorted armature coils. That means an armature replacement or a look for a cheap second-hand HP1500 on eBay as a spare part source.
A second sign of armature trouble will be visible on the brushes. When longer than 6 mms, they will not be worn entirley yet and the sparking will not have been caused by that. When one of their edges is eaten away (the trailing edge, where it leaves the copper strips), that is a sign of a current way too high. The loss of power is in that case caused by heat generated by the shorted windings (which act like shorted secondary windings in a transformer, which is basically the same as what happens in a spot-welding machine). This heat from induced shorting current absorbs output power from the motor, which loses strength and rpm.
A third reason for abnormal sparking (and it that case the armature can still be okay) may be a blown radio noise suppressor condensor. After a few years of heavy service, this part can literally blow up sometimes. This often occurs when the motor is switched off while under heavy load, precisely at the moment that the AC sine wave of the 230 volts reached maximum. Due to the strong current and magnetic field, a high peak voltage is generated at that moment of switch-off, reaching or overstepping the threshold voltage of the condenser. It will fail at that same moment or one of the next times the drill is used. This condenser suppresses the sparks and without it, the sparks will be much bigger and your tool will be audible through FM radio broadcasts in a 200 yards radius.
So your best bet is to have a look inside, at the commutator strips, the brushes themselves and the condenser. Don't use the drill before you are sure, or you may loose the electronics and the motor field windings as well.
Good luck and do ask me for any advice you want!
2nd Jun 2008, 07:43 AM #5
What Gerhard said but something extra: it could well be the field. I've had field trouble on a Makita HR2220 rotary hammer and on a 3612BR router - both of which I picked up in eBay. Luckily I have a number of both of these machines and was able to determine the problem through trial and error.
Nice too 'cause a field is a lot cheaper than an arbour...
DamienIs it wrong to be in love with a sawbench?
2nd Jun 2008, 07:29 PM #6
I'm going to try replacing the bushes first. I think they look a bit worn but I haven't seen them in original condition...thanks for the heads up on the parts being loosely mounted in the chassis.
7th Jun 2008, 07:04 AM #7
Bushes replaced, general clean and tidy up inside the case and all fixed.
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