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Forum topic by yammi450 posted 01-16-2012 01:46 AM 2348 views 0 times favorited 10 replies Add to Favorites Watch
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yammi450

25 posts in 2121 days


01-16-2012 01:46 AM

I picked up a used Delta bandsaw 28-203 with riser on craigslist, and have a quick question. When I plug it in, there is a slight humming sound with the saw off. I can here it as I plug it in. I can’t tell where exactly it’s coming from but I suspect the switch. Also, there is no resistance to the on button when it’s not pluged in. Is there something about the switch that the power activates it? It also runs fine when on.


10 replies so far

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Loren

8293 posts in 3107 days


#1 posted 01-16-2012 02:00 AM

It may be a magnetic switch. They have mechanical designs that can get
kind of tweaky.

Open the switch and blow it out, check for mechanical problems. Sounds
like the switch is letting some voltage through.

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yammi450

25 posts in 2121 days


#2 posted 01-16-2012 02:56 AM

I opened up the switch and it is a magnetic switch and seems to work fine. I also opened the panel box and there’s transformers, relays, juction boxes, but no kichen sink. all the wiring looks fine and the motor is whats humming( not like its trying to run, but more like a relay sound). Is this normal? If not where do I start to find the problem?

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yammi450

25 posts in 2121 days


#3 posted 01-16-2012 04:14 AM

I looked at it agai, and it’s either the transformer or the relay. Seeing how the humming is there before the relay is tripped by the switch I think the transformer is the niose. Is it normal for a transformer to hum? I just don’t want to leave this pluged in if it’s going to cause damage to the remaining parts, or worse cause a fire.

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EEngineer

1059 posts in 3072 days


#4 posted 01-16-2012 04:32 AM

Cheap transformers will hum. Transformer cores are generally made from thin sheets of steel to shorten eddy current paths and limit core losses. If these laminates are loose, they will vibrate at the 60 Hz line frequency and cause that hum.

It really doesn’t cause any problems but if it annoys you enough I would disassemble the mag switch and retighten all the mounting hardware. Sometimes the transformer core laminates have screws that squeeze the laminates together and these may work loose over time. Loc-tite them and tighten them down. Cheaper transformers may just have a metal frame that is assembled around the laminates. These are usually just clamped around the laminates but often have a coating of shellac to immobilize the laminates and minimize hum. I have had good luck with other noisy transformers just applying another coat of shellac to the laminates and reassembling the transformer while it is still tacky.

Good luck!

-- "Find out what you cannot do and then go do it!"

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Mickey Cassiba

312 posts in 2491 days


#5 posted 01-16-2012 04:37 AM

There shouldn’t be any noise until you close the switch…your contractor may be hanging…or even welded on one leg.

-- One of these hammers oughta fix that...

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yammi450

25 posts in 2121 days


#6 posted 01-16-2012 04:53 AM

The transformer ia a delta original. I’ll have to take another look and see if I could tighten the up or not.
As far as the contactpoints , I can see them all moving from the bottom side when I power on and off.
I’ve disconected the motor completly and it still hums when its pluged in, So im sure its not the motor. I’ve done the same with the switch so I can rule that out too. The hummmmm doesn’t bother me it’s just the chance of additional damage that worries me.

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ChunkyC

856 posts in 2713 days


#7 posted 01-16-2012 04:56 AM

Transformer buzz. They all do it. It’s not a sign that the transformer is bad. It’s just broken welds on the laminations in the transformer core.

-- Chunk's Workshop pictures: http://spadfest.rcspads.com/thumbnails.php?album=135

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yammi450

25 posts in 2121 days


#8 posted 01-16-2012 06:29 AM

Thanks for the information. Before I opened the back panel I thought I had a problem. I didnt know all that stuff was in there. I thought it was a simple 110 hookup and it was the motor humming. If all is normal I won’t worry about it.

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Tyrone D

314 posts in 1792 days


#9 posted 01-16-2012 12:34 PM

It’s normal for a transformer to hum. The copper wire wound around the core gets loose. If you are experienced you can shim the windings so they don’t move around. I’ve never done it and never will do it. I will also never recommend it, it’s too risky. I’d rather have a humming transformer than a transformer with a wrecked coil because I slipped.

-- --Tyrone - BC, Canada "Nothing is ever perfect, we just run out of time."

View Bill White's profile

Bill White

4448 posts in 3420 days


#10 posted 01-16-2012 06:59 PM

Remember that if it is humming, it is using electricity and that equals power consumption. Not tryin’ to sound like a wierd “greener”, BUT $ IS $.
Bill

-- bill@magraphics.us

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