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Fulci 20th November 2012 12:08 PM

Silmic 4.7uF 63v unavailable - Can I use 4.7/50v or 10uf 100v?
Hi everyone!

My dealer can't seem to provide Elna Silmic II in 4.7uF 63v. He does have 4.7uF 50v and 10uF 100v? Can I use either of these? What could happen if I placed the 10uF?

This is for the power section of my Audiolab 8000A, the original are 63v but these are the only caps in all the amp that are 63v, all others are under 50v, including PSU. I have already replace all the other caps to a remarkable improvement, just these are the last 4 caps remaining.

There are some chinese sellers on ebay or outside it, could these be trustworthy or are most probably fakes?

PC MotherBoard Capacitors Store

Or is Headfishop a good seller?

If I were to replace those 4.7uF 63v with film types, can I use a smaller value? What would be a good capacitance for that?

Thank you!

Mooly 20th November 2012 12:51 PM

Without knowing what there function is its not possible to say with any certainty. I would first of all measure the actual voltage these caps have across them when the amp is on and take that as a starting point for determining the working voltage needed.

Fulci 20th November 2012 06:09 PM

Well... The schematics is a bit different from what is in the amp, as mine's a later revision, so I don't know what it's function is really. Two of these do not appear in the schematics.

I will try to get a multimeter and measure it's voltage. I am almost sure 50v will do but I'm kind of afraid of peaks and capacitors lifetime.

Fulci 22nd November 2012 11:47 AM

What would happen if I were to use a 10uf/100v?

Also, if using film caps, can I get a smaller capacitance?

Mooly 22nd November 2012 12:06 PM


Originally Posted by Fulci (Post 3251596)
What would happen if I were to use a 10uf/100v?

Also, if using film caps, can I get a smaller capacitance?

What would happen ! Well that depends on what it does. If its rail decoupling then no problem. And you should be able to determine that just by looking at the PCB and where it goes :)

If its not directly across a rail then it does something else...
If its in the audio path somewhere a time constant will be altered. If it were a timing cap for say a switch on delay you might end up waiting twice as long for the amp to come on. If its in a DC protection circuit it might make the delay detecting a DC offset fault longer.

Do you see :) Its an impossible question to answer without seeing the amp or the correct circuit.

Film caps should be available in 4.7uf from many sources I would have thought.

Fulci 28th November 2012 03:54 PM

So I finally got a multimeter and it rates at 41.8V... Can I use the 50v caps then? What is the peak value for the Silmic II 50v? Can they explode?

Also, I honestly don't know what these caps are for, all I know is that I accidentaly broke one the caps legs and the amp continued to function perfectly. My guess these are the caps that have no value in the scheme that are place in the Pre-Amp in line of the amp.

Mooly 28th November 2012 05:42 PM

For what we deal with here the peak working voltage of the cap is the same as it DC voltage rating. So peaks of 50 volts are OK for a 50 volt cap. The 50 volts is an absolute max rating. 42 volts is perfect, no problems.

(For applications where the cap is across AC the ratings are sometimes very different but that won't apply here)

So no problems :)

Fulci 28th November 2012 05:45 PM

Ok thanks! It hasn't blown up yet, so I guess I'll be fine.

Now, I wonder why those chaps at Audiolab used the 63v here when every other cap is 50v max. It'd be cheaper for them to use the 50v as there are another 12 at least with that value.

Mooly 28th November 2012 06:10 PM

Can't answer that without seeing the circuit and knowing all the details but a constant 42 volts DC is absolutely safe on a 50 volt cap.

Fulci 28th November 2012 06:11 PM

Great! Thanks!

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