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Bought Massage Chair Blowing Fuses Capacitor Destroyed

Mrtelectric

Aug 12, 2020
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Hi. First post here. Start off let me tell you I am a licensed electrician but not too much experienced with electronic boards. Get right to the point. Purchased an expensive massage chair in an auction and was extremely excited to receive today. But, when I finished the set-up no power. Took out fuse, blown. Now this kinda scared me because why was it blown to begin with? So I just installed another glass time delay fuse and and flash boom. So took apart didn't see any signs of any shorts nothing on wire but looked closely at where the flash came from and it was directed in front of power cord connection at the capacitor. Any suggestions much appreciated thank you?
 

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Mrtelectric

Aug 12, 2020
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BTW...I wiped off a little soot off yellow capacitor and I clearly see a hole in it.
 

Mrtelectric

Aug 12, 2020
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Hi. First post here. Start off let me tell you I am a licensed electrician but not too much experienced with electronic boards. Get right to the point. Purchased an expensive massage chair in an auction and was extremely excited to receive today. But, when I finished the set-up no power. Took out fuse, blown. Now this kinda scared me because why was it blown to begin with? So I just installed another glass time delay fuse and and flash boom. So took apart didn't see any signs of any shorts nothing on wire but looked closely at where the flash came from and it was directed in front of power cord connection at the capacitor. Any suggestions much appreciated thank you?
Is this a safety capacitor?
 

Martaine2005

May 12, 2015
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Hi Mrelectric, it looks like a thermistor. You can use your multimeter and check for a short across the live and neutral lines.
If shorted, remove it from the PCB and check the lines again for a short.

Martin
 

Martaine2005

May 12, 2015
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The X2 safety cap is the yellow topped rectangular component next to the blown component.

Martin
 

Mrtelectric

Aug 12, 2020
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Hi Mrelectric, it looks like a thermistor. You can use your multimeter and check for a short across the live and neutral lines.
If shorted, remove it from the PCB and check the lines again for a short.

Martin
Thanks Martin for the reply back. Very much appreciated. I was just thrilled to finally to get my chair I waited forever to finally get but I just got a disappointed lemon. But damn I will try to figure this out to get some hope back. I figure it is a positive lead dead shorted somewhere to the chair frame but once that power plug is connected to board I have no idea where to find any short. I do know there is no short in cord coming to board. That thermistor is also closed I have continuity thru it, not sure it suppose to or not.
 

Martaine2005

May 12, 2015
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I am sure, you being the sparky, can find the short.
I would start looking at areas where the wires are near moving parts and could get snagged/damaged.
But you need to also know whether the board has a short on it.
The thermistor (if it is one) will have resistance that changes if you heat it. But it has a hole anyway. Disconnect the chair from the board and power up the board through a series incandescent bulb. If it lights bright, the board has a short.

Martin
 

Mrtelectric

Aug 12, 2020
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I am sure, you being the sparky, can find the short.
I would start looking at areas where the wires are near moving parts and could get snagged/damaged.
But you need to also know whether the board has a short on it.
The thermistor (if it is one) will have resistance that changes if you heat it. But it has a hole anyway. Disconnect the chair from the board and power up the board through a series incandescent bulb. If it lights bright, the board has a short.

Martin
I would imagine I would need to replace that thermistor...
 

Martaine2005

May 12, 2015
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Can you see any reference on the PCB or symbol next to the component?.
Can you see how it’s connected?. Is it inline or is it across the the live and neutral?. It could be a MOV.
If inline (series), for testing purposes only, you can short the thermistor.
If a MOV, you can cut it out of circuit, for testing purposes. Still, use the bulb limiter when testing.
 

Mrtelectric

Aug 12, 2020
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I went ahead and plugged power cord (end of cord at board from fuse) into board and rang out the end of the power cord and no continuity so that tells me no short at board/cord...no signs of short at board ringing thru components...even thou evident thermistor has hole in it...I wonder if I used wrong fuse replacement... 5a/240v/time delay I used...do you think the time delay caused the thermistor to burn out?..sent more pictures...I cannot see any evidence of short on any wires in chair and from my line of work that's where the arc would come from...
 

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Mrtelectric

Aug 12, 2020
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I went ahead and plugged power cord (end of cord at board from fuse) into board and rang out the end of the power cord and no continuity so that tells me no short at board/cord...no signs of short at board ringing thru components...even thou evident thermistor has hole in it...I wonder if I used wrong fuse replacement... 5a/240v/time delay I used...do you think the time delay caused the thermistor to burn out?..sent more pictures...I cannot see any evidence of short on any wires in chair and from my line of work that's where the arc would come from...
Added another picture of complete wiring under chair...the board I pulled goes behind the other board...
 

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Martaine2005

May 12, 2015
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Judging by your new photos, the device with a hole is a MOV (varistor).
It is possible that it was shorted and now it’s blown open circuit.
Can you power up the board without chair connected?.

Martin
 

Ngineer

Aug 14, 2020
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A service manual or schematic would be helpful, but if you can't find one you'll just have to trace out the circuit and draw your own schematic so that you can make sense of it. Looking at the photos it appears most of the controls are electronic using mosfets rather than relays and you are probably getting a little out of your depth, being unfamiliar with this technology. It really is a job for an electronic technician with a service manual but if you proceed carefully with proper advice you may be able to fix it yourself. Being a licenced electrician you would already be aware of the dangers.

I see you have already removed the board from the chassis and suggest as a first step that you trace out the board and draw a partial schematic of the power input circuit.

1. Unsolder the blown component (probably an MOV surge suppressor if in parallel with the mains. If in series it is probably a thermistor to limit inrush current to the primary of the toroidal power transformer).
2. Clean away all carbon deposits from the board and surrounding components. (If they remain after mains power is applied you will get tracking across the top surface of the PCB leaving a permanent breakdown path)
3. Wire a low wattage bulb in series with the mains lead going to the board and apply power for a bench test.
If the bulb lights something is blown/shorted and you need to look at your schematic to work out what might be causing the short.
A multimeter will help you test individual components and check voltages.

Give that a try and let us know how you go!
 

Mrtelectric

Aug 12, 2020
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A service manual or schematic would be helpful, but if you can't find one you'll just have to trace out the circuit and draw your own schematic so that you can make sense of it. Looking at the photos it appears most of the controls are electronic using mosfets rather than relays and you are probably getting a little out of your depth, being unfamiliar with this technology. It really is a job for an electronic technician with a service manual but if you proceed carefully with proper advice you may be able to fix it yourself. Being a licenced electrician you would already be aware of the dangers.

I see you have already removed the board from the chassis and suggest as a first step that you trace out the board and draw a partial schematic of the power input circuit.

1. Unsolder the blown component (probably an MOV surge suppressor if in parallel with the mains. If in series it is probably a thermistor to limit inrush current to the primary of the toroidal power transformer).
2. Clean away all carbon deposits from the board and surrounding components. (If they remain after mains power is applied you will get tracking across the top surface of the PCB leaving a permanent breakdown path)
3. Wire a low wattage bulb in series with the mains lead going to the board and apply power for a bench test.
If the bulb lights something is blown/shorted and you need to look at your schematic to work out what might be causing the short.
A multimeter will help you test individual components and check voltages.

Give that a try and let us know how you go!

after ringing out and inspecting every wire the short was coming from that
Judging by your new photos, the device with a hole is a MOV (varistor).
It is possible that it was shorted and now it’s blown open circuit.
Can you power up the board without chair connected?.

Martin
Judging by your new photos, the device with a hole is a MOV (varistor).
It is possible that it was shorted and now it’s blown open circuit.
Can you power up the board without chair connected?.

Martin
 

Mrtelectric

Aug 12, 2020
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After ringing everything out the only short was coming from that MOV...I removed that MOV from the board and plugged the chair back in to power up and now the chairs works perfectly. I will try to find the replacement MOV or leave out and plug chair into a surge protector and a smaller rated system chair fuse.
 

Mrtelectric

Aug 12, 2020
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Judging by your new photos, the device with a hole is a MOV (varistor).
It is possible that it was shorted and now it’s blown open circuit.
Can you power up the board without chair connected?.

Martin
You’re welcome.[/QUOTE
]is this MOV for surge protection?...Crazy how you can remove it from circuit board and doesn't effect anything...
 

Martaine2005

May 12, 2015
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Yes, it’s to suppress transient voltages.
It’s designed to fail short circuit and blow the fuse. Hence removing it, removes the short.

Martin
 
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