Rob Flinn

RFI RC filter
« on: August 15, 2020, 09:53:23 AM »
I have a QUAD 44 hifi preamp on the bench at the moment which has a popped RFI filter capacitor thingee.   See pic. 

I don't seem to be able to find one that is this exact same spec 47n/1K from my usual suppliers.   

1. Is the spec particularly important ?
2. Is the filter itself particularly important ?   Will the owner notice a difference if I just leave it out ?
regards Rob


JohnRoberts

Re: RFI RC filter
« Reply #1 on: August 15, 2020, 10:27:43 AM »
Manufacturers rarely put in extra components for no reason.

Can you replicate a replacement from two parts? The electrons may not notice.

JR
It's nice to be nice....

RuudNL

Re: RFI RC filter
« Reply #2 on: August 15, 2020, 10:30:07 AM »
Is that one of the infamous RIFA capacitors/filters, that always 'explode' after some time?

I just looked at the schematic of the Quad 44 power supply, but I don't see this component.
« Last Edit: August 15, 2020, 10:35:33 AM by RuudNL »
There is a solution for every problem!

http://www.vansteenisaudio.nl

Khron

Re: RFI RC filter
« Reply #3 on: August 15, 2020, 10:34:50 AM »
Looks indeed like one of those doomed-to-fail metallized paper ones.

Just about any X2 rated cap of the same value should do fine. Assuming that's an RF-filter on the mains input?

Is that one of the infamous RIFA capacitors, that always 'explode' after some time?
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

moamps

Re: RFI RC filter
« Reply #4 on: August 15, 2020, 10:57:01 AM »
I just looked at the schematic of the Quad 44 power supply, but I don't see this component.
Look again. :)

rackmonkey

Re: RFI RC filter
« Reply #5 on: August 15, 2020, 11:21:16 AM »
Is that one of the infamous RIFA capacitors/filters, that always 'explode' after some time?

Definitely is. Seems like they all burst open along the same axis. I’ve collected all of the ones I’ve replaced just for grins and they all physically look like this, with the split horizontally across one side.

A lesson in the importance of material selection. The resin they used was rigid and lacked the flexibility needed for temp-related expansion and contraction. Over time, a hairline crack develops, moisture comes in and BOOM. Out comes the (nastiest smelling) white smoke.
Whether you think you can or you think you can't, you're probably right.

squarewave

Re: RFI RC filter
« Reply #6 on: August 15, 2020, 12:08:27 PM »
Over time, a hairline crack develops, moisture comes in and BOOM. Out comes the (nastiest smelling) white smoke.
This is a pretty funny video:

  https://www.youtube.com/watch?v=NMI9BSXztuc

The action is at ~3:30. I love the guy's reaction. Just open the window.

Rob Flinn

Re: RFI RC filter
« Reply #7 on: August 15, 2020, 12:33:22 PM »
Yes it's a Rifa 47n in series with 100R.  I can get a RIFA replacement for £1.39 so I guess I will go with that, & be prepared to replace it again in another 20 years....
regards Rob

RuudNL

Re: RFI RC filter
« Reply #8 on: August 15, 2020, 12:46:48 PM »
Look again. :)

Yes, you are right...  :P
(But it wasn't on the schematic that I found.)
« Last Edit: August 15, 2020, 12:49:55 PM by RuudNL »
There is a solution for every problem!

http://www.vansteenisaudio.nl

rackmonkey

Re: RFI RC filter
« Reply #9 on: August 15, 2020, 01:07:21 PM »
This is a pretty funny video:

  https://www.youtube.com/watch?v=NMI9BSXztuc

The action is at ~3:30. I love the guy's reaction. Just open the window.

LOL. Yes! That! Been there!

Why doesn’t he pull the plug immediately??
Whether you think you can or you think you can't, you're probably right.


RuudNL

Re: RFI RC filter
« Reply #10 on: August 15, 2020, 01:16:26 PM »
Lots of smoke. "But that doesn't mean anything"...
There is a solution for every problem!

http://www.vansteenisaudio.nl

rackmonkey

Re: RFI RC filter
« Reply #11 on: August 15, 2020, 01:18:32 PM »
Lots of smoke. "But that doesn't mean anything"...

I guess this is why the X2 spec was created  :o
Whether you think you can or you think you can't, you're probably right.


 

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