I bought a used Ryobi 16" scroll saw several years ago and just used it the first time last week. I ran it for 5 minutes and shut it off, when I went to start it again it tripped the breaker, nothing else plugged into that breaker, reset 20a breaker, tripped again. Motor turns easy by hand, don't smell anything burnt, I took the control panel off and see nothing wrong or burnt. I ohm'ed the switch, it's good, checked voltage at power cord at 122v, wasn't sure how the test anything else on the circuit board but nothing looks burnt or bulging. I checked the brushes on the motor and they look hardly worn, I may not have tested the motor properly so I ordered a new one anyway. I bypassed the circuit board to make a direct connection to the motor just to see if it would spin, when connected the motor just vibrated back and forth really fast. So yesterday I get my new motor installed and it immediatley trips the breaker. What am I missing?
Scroll Saw Tripping Breaker
- Thread starter drew67
- Start date
rlitman
Well-known member
Is it a GFCI or AFCI breaker?
rlitman
Well-known member
Oh well, that was worth a shot at least.
Is the plug grounded? Sounds to me like something in the machine is shorting to ground when you energize the switch.
Is the plug grounded? Sounds to me like something in the machine is shorting to ground when you energize the switch.
Empty Pockets
Well-known member
That could be why the other guy sold it. maybe a bad switch?
Can you post a picture of the control board? A brush motor is also called a universal motor and should work on AC or DC. Try the new motor direct wired. If it doesn't run instantly don't try it again.The old motor may have blown and taken out the control board. Try plugging in the saw without the motor. Does
It pop the breaker? If it does, disconnecr the control board and try again. You find the problem by process of elimination.
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It pop the breaker? If it does, disconnecr the control board and try again. You find the problem by process of elimination.
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I just got a look at the control board on Ereplacementparts. From what I could see in the fuzzy picture there is a ********* square on the board that is a bridge rectifier. There should be a + and a- on diagnsl corners and it should say AC or have symbol of a sine wave on the other two diagnal corners. measure across the pins on each side both ways if any of them measure close to zero in both directions, it is blown. The ste sys the board is discontinued but I may not be looking at the right machine. Do this with 5he board disconnected. Do this before trying the motor. It is a better bet
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One thing I noticed last night was I had screwed the board and front panel back on and turned it on one last time, there was a definite pop inside when the breaker tripped which it hadn't done before when the breaker tripped. I reset the breaker and tried again, no trip. When I took the board back out there were slight burn marks on the bottom of the board. So I unhooked the motor wires and turned it on, no trip. I hook the motor wires directly to the power wires, again just like original post, motor vibrating back and forth. Voltage good through switch. Checked ohmes on bridge rectifier, yes, one test was .3, the others were about 16.0. So I'm probably ordering a board but what about the motor vibrating or shaking back and forth?
If it is a brush motor and won't run on AC, ya got me. Where did you find a board? 16 ohms is normal in the forward direction. Reversing the probes, the readings should be much higher. The real low resistance will probably read that low both ways. It is shorted, the first component off the AC line and will blow the fuse in a heartbeat. If the board is expensive or hard to obtain, those rectifiers are very cheap.[/URL][/IMG]
One thing I noticed last night was I had screwed the board and front panel back on and turned it on one last time, there was a definite pop inside when the breaker tripped which it hadn't done before when the breaker tripped. I reset the breaker and tried again, no trip. When I took the board back out there were slight burn marks on the bottom of the board. So I unhooked the motor wires and turned it on, no trip. I hook the motor wires directly to the power wires, again just like original post, motor vibrating back and forth. Voltage good through switch. Checked ohmes on bridge rectifier, yes, one test was .3, the others were about 16.0. So I'm probably ordering a board but what about the motor vibrating or shaking back and forth?
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The nice part of helping somebody else is that you learn stuff yourself. I just did some quick research and found out why your motor wont run on AC. I was familiar with series type brush motors. One brush is connected to the line and makes contact with the rotor. The other brush contacts the rotor and is connected to rhe stationary or stator winding. The other side of the stator goes to the other side of the line. In a paralell set up the two brushes go to the line as well as the leads off the stator. According to what I just read this will just result in humming if connected to AC. BINGO!! You have a parallel wound DC motor that will only run on DC, supplied by that blown bridge rectifier
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rlitman
Well-known member
Yep. The bridge rectifier is that black square on the board with the hole in the middle, and one corner beveled. A replacement can probably be found for under $5 if you feel like soldering.
vtwinjunkie
Well-known member
Might be a silly question....but how old is that breaker?
I found a board on Tool Parts Direct... http://www.toolpartsdirect.com/ryobi-sc165vs-scroll-saw.html for $16, since it's relatively cheap and there are burn marks on the board I'll just order a new one. As for the breakers age, maybe 10 years old
No question is silly. That is how we learn. He popped the breaker after 5 minutes the first time. Presumably, that is when the rectifier shorted. Now it pops instantly. Power rectifiers are often right across the line and that is the first thing I check when a device is popping the breaker. Rectifiers, triacs in lamp dimmers and speed controllers, output transistors in Hi Fis are the components that handle the power and they are usually the ones that fail. If you look at his control board you will see a device on a heat sink on the far corner. That is the triac that controls motor speed and was suspect number 2.
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