question on spark suppressor capacitor

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question on spark suppressor capacitor

Postby TheAnalogSource » Mon Mar 05, 2012 8:49 am

Hi all,

most old turntables has a capacitor in parallel with the switch. i think this is meant to suppress spark upon contact preventing deterioration of contact point.

however example if the switch is in the off position, isn't it that current will pass through the capacitor when charge is filled up leading to supply of current to the motor. then if the motor is not spinning, there will be a heat buildup in motor stator.
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Re: question on spark suppressor capacitor

Postby Remus » Mon Mar 05, 2012 9:28 am

most old turntables has a capacitor in parallel with the switch

They are called snubbers, and usually consist of a resistor and capacitor in series. Single package assemblies are available hence they may appear as single component only.

i think this is meant to suppress spark upon contact preventing deterioration of contact

On the contrary, they function during switching off and not during switching on.

however example if the switch is in the off position, isn't it that current will pass through the capacitor when charge is filled up leading to supply of current to the motor.

This will only happen if the snubber is defective.

then if the motor is not spinning, there will be a heat buildup in motor stator.

It depends on how defective the snubber is: the platter may spin as soon as you plug in the power chord even with the switch at off position; or after some playing time, the platter may continue spinning even if switched off; or after being left plugged for some time the platter may spin by itself (while switched off). Heat will build-up if the motor is mechanically prevented from spinning.

You can check for leaked voltage on the motor terminals. You can verify effectivity of the snubber by observing the switch contact for sparks while switching on/off in the dark.
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Re: question on spark suppressor capacitor

Postby TheAnalogSource » Mon Mar 05, 2012 9:51 am

if it is a resistor and capacitor in series inside...then still the same question...if the capacitor charge capacity is filled up...then the electricity will flow. what will inhibit the electricity to flow if the parralleled switch in not shorted.


also if it is damaged then is it safe to assume that the capacitor side is the damage portion because if its the resistor then the line will now be open...or pwede ba damage ang resistor tapos bumaba lang resistance. follow up question...if the capacitor is damaged then either... the line is open then the electricity will not flow.....or there will be no charge capacity thus electricity will instantly flow.
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Re: question on spark suppressor capacitor

Postby tony » Mon Mar 05, 2012 12:20 pm

TheAnalogSource wrote:if it is a resistor and capacitor in series inside...then still the same question...if the capacitor charge capacity is filled up...then the electricity will flow. what will inhibit the electricity to flow if the parralleled switch in not shorted.


also if it is damaged then is it safe to assume that the capacitor side is the damage portion because if its the resistor then the line will now be open...or pwede ba damage ang resistor tapos bumaba lang resistance. follow up question...if the capacitor is damaged then either... the line is open then the electricity will not flow.....or there will be no charge capacity thus electricity will instantly flow.



in the open switch position current will flow to the rest of the circuit, the question is, is the current large enough to cause the motor to run? if the motor thus the plater does not move, then we know that the current is low enough to matter....

as remus explained, the snubers are intended to arrest the sparking during switch off, because if there is sparking, the switch contacts will be eroded, and in time contacts will become high resistance instead of a short that it was intended to be....so a damaged cap might lead to a damaged switch....
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Re: question on spark suppressor capacitor

Postby TheAnalogSource » Mon Mar 05, 2012 4:43 pm

thanks tony....but example there is a correct value of resistance and capacitance in the snubber such that the motor will not spin at switch open position.

....but since there is current passing thru the motor...isnt it also follows that the motor will heat up or the resistor/capacitor will fail being a close system if the system is plug in for a long time? if the resistor/capacitor fails...ok lang because it would mean that it will become an open system....but what worries me is the motor heat buildup because then it would make them fire hazard if continuously plug in.

...on a side note, the newer system have the same snubber in series with the switch and the motor. Would you think it is a better layout?


sorry i may not be using the right term but i think you'll get my point.
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Re: question on spark suppressor capacitor

Postby tony » Mon Mar 05, 2012 4:52 pm

TheAnalogSource wrote:thanks tony....but example there is a correct value of resistance and capacitance in the snubber such that the motor will not spin at switch open position.

....but since there is current passing thru the motor...isnt it also follows that the motor will heat up or the resistor/capacitor will fail being a close system if the system is plug in for a long time? if the resistor/capacitor fails...ok lang because it would mean that it will become an open system....but what worries me is the motor heat buildup because then it would make them fire hazard if continuously plug in.

...on a side note, the newer system have the same snubber in series with the switch and the motor. Would you think it is a better layout?


sorry i may not be using the right term but i think you'll get my point.


the fact that the plater does not move at all in off position is a proof that there is nothing to worry about....a broken capacitor will manifest itself with obvious signs like burn marks, bulging and corrosion, even to the untrained this is easy to see....

better lay-out? if your player is still alive after all these years, that is a testament to good engineering....
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Re: question on spark suppressor capacitor

Postby Remus » Tue Mar 06, 2012 7:58 am

if the capacitor charge capacity is filled up...then the electricity will flow.

Again, on the contrary, if you connect a capacitor in series with a load and supply it with electrcity, a very small amount of current will flow thru the capacitor and the load for a very short period of time (depending on the size of the capacitor or the electricity applied) as the capacitor charges up. When the capacitor is fully charged, the flow of current will stop.

because then it would make them fire hazard if continuously plug in

It is always safer to unplug any electrical device that is not being used. However, if you are inconvenienced by plugging/unplugging, then a cut-off switch may be installed.
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Re: question on spark suppressor capacitor

Postby TheAnalogSource » Tue Mar 06, 2012 8:16 am

Remus wrote:
if the capacitor charge capacity is filled up...then the electricity will flow.

Again, on the contrary, if you connect a capacitor in series with a load and supply it with electrcity, a very small amount of current will flow thru the capacitor and the load for a very short period of time (depending on the size of the capacitor or the electricity applied) as the capacitor charges up. When the capacitor is fully charged, the flow of current will stop.


ah ok...dito ako nalito...i was thinking the other way around. thanks.
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Re: question on spark suppressor capacitor

Postby tony » Tue Mar 06, 2012 11:01 am

It is always safer to unplug any electrical device that is not being used. However, if you are inconvenienced by plugging/unplugging, then a cut-off switch may be installed.


very good advice, i myself do this as a matter of practice and energy conservation......


Again, on the contrary, if you connect a capacitor in series with a load and supply it with electrcity, a very small amount of current will flow thru the capacitor and the load for a very short period of time (depending on the size of the capacitor or the electricity applied) as the capacitor charges up. When the capacitor is fully charged, the flow of current will stop.



this true for dc voltages....for ac wherein polarity changes 60 times per second, there is current flow due to charge-discharge cycles....again this is no cause for concern......and the best thing to do is unplug your equipment when not in use....
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Re: question on spark suppressor capacitor

Postby philpath » Tue Mar 06, 2012 3:46 pm

LUMA na kasi mga "idler turntables" at di pa uso nun ang electronic switching or small relays!!!!!! Hahahahahaha ;) ;) ;) ;) ;)
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Re: question on spark suppressor capacitor

Postby tony » Tue Mar 06, 2012 3:57 pm

philpath wrote:LUMA na kasi mga "idler turntables" at di pa uso nun ang electronic switching or small relays!!!!!! Hahahahahaha ;) ;) ;) ;) ;)


these turntables used shaded pole ac motors, very, very, very low power consumption.... 8)
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