Akai RC Snubber Replacement

[GaryJarcia]

Hey all,

I've been doing my research on spark quenchers / RC snubbers to replace the 120R + .1uf 500VAC snubber in the Akai 280D-SS i'm restoring.

Initially I wanted to replace the original part "RU1201" (Listed as CR101 & 102 on the schematic) with "RE1201" but the voltage rating listed on the 280D-SS schematic is "500VX2." I'm assuming this means a 500VAC X2 rated capacitor, but the RE1201 I planned on replacing it with is listed as 275VAC rating, so that seems to be a no go.

To my understanding, RC snubbers have a high operation frequency so I was planning on replacing the RC snubber with a Nichicon .1uf 500VAC cap & 120R CDE 3W resistor. However, I cannot find information about the saftey ratings of this capacitor: https://www.mouser.com/ProductDetail/Nichicon/PPA1853100KG?qs=vmHwEFxEFR/GbSRP8To9qw==

I will be transparent, i'm an EE student just beginning my career and am having difficulty identifying if these are good replacements or not. Any assistance would be much appreciated!

Thanks so much

 

[jlb2]

Hi Gary. These capacitors are connected between the phase and the neutral of the mains, so they must be X2 (or X1) type. Those are guaranteed, should they fail, to do it in a way that does not compromize safety. A non-safety capacitor is potentially dangerous even if they have a higher voltage rating. 275 VAC is more than enough for those caps that will not see more than 110 volts, the important thing is "X2". But you are correct that it is best to avoid replacing a component by another component with inferior ratings. The only reasons I can imagine for using 500V caps there, are either that the motor switching can generate high voltage pulses through the snubber, or that the manufacturer just used parts that were available at a time when 275V X2 caps were out of stock.

BTW why do you need to replace these caps? Any trouble with them?

 

[GaryJarcia]

Hi Gary. These capacitors are connected between the phase and the neutral of the mains, so they must be X2 (or X1) type. Those are guaranteed, should they fail, to do it in a way that does not compromize safety. A non-safety capacitor is potentially dangerous even if they have a higher voltage rating. 275 VAC is more than enough for those caps that will not see more than 110 volts, the important thing is "X2". But you are correct that it is best to avoid replacing a component by another component with inferior ratings. The only reasons I can imagine for using 500V caps there, are either that the motor switching can generate high voltage pulses through the snubber, or that the manufacturer just used parts that were available at a time when 275V X2 caps were out of stock.

BTW why do you need to replace these caps? Any trouble with them?

Thanks so much for your thorough response! I will be sure that the replacements are a specified X2/X1 rated capacitor. I wanted to replace them as they had some sort of white fluidish material around the base and they have both drifted down to 85uf and 90uf. As i'm not having any issues, i'll likely use them until I begin to have issues. I can imagine maybe the 500VAC cap was a good choice as the deck includes a 220V option for export models? Just a guess.

 

[jlb2]

You are welcome You are correct, X-type capacitors are not one of the types that go bad with time, I would leave them alone unless they show signs of aging (cracks, burns, etc.). As for the voltage rating, those that we use in Europe are 275 VAC too, that's more than enough for our 230-240 VAC mains voltage. 500 VAC rated caps would only be needed for 3-phase machines, but it's not the case here. the more I think about it, the more I think it was just a matter of availability, with inductance-generated pulses as a remote possibility. If someone can check the caps in another 280D with a very different serial, that would hlep decide between the two options.