Capacitor help

geowhitt · 3rd June 2008, 05:22 PM

Hi to all, this is my first post and its a help me sorry.
I am going to re cap my moth power amps and i have found a shop that has most parts in stock, my problem is which caps to use.
The caps fitted to the amps are samhwa 4700uf 63v and there is 2 others which are 470mFD 16v and 470uf 63v.
My question is what is uf and mFD i have been told that 2 of the caps are feedback caps and have to be right i need to know what the parts are before i send a order off as i dont want to blow up the amps.
Hope this makes sense

Netlist · 3rd June 2008, 05:41 PM

mFD is often used instead of µF. It's a source of confusion as mF is in fact milli(F) and uF or µ(F) is micro(F).

So, both caps are most likely 470µF.
A picture would give more certainty.

Here's a nice page on capacitors:
http://www.uoguelph.ca/~antoon/gadgets/caps/caps.html

/Hugo

geowhitt · 3rd June 2008, 06:07 PM

Thanks for that,its like school again!!!!!!!! lots of reading.
Thanks.

trodas · 6th June 2008, 08:18 AM

Another interesting thread (tough more specific about known bad caps and their replacement on voltage filtering circuits) are there:
http://capsmod.net/forum/viewthread....extra=page%3D1

geowhitt · 9th June 2008, 03:47 PM

Thanks for the replys.
I have changed the caps and the feedback caps,only to still have a small problem!!!!!.
When i first switch the amps on i get a hum/buzz sound that last for a few seconds and the amps go quite and i then can use them.
The noise is only there when first switched on.
I thought the noise was a cap problem thats why i changed them and also there were 20yrs old.
So i am at a loss now as to were to look on the amp for the problem.
Any help please.
The amps are Moth 100 watt mono amps.

trodas · 10th June 2008, 08:43 PM

I would start replacing all the caps, becuase they are likely to be dried out already. 20 years can last only quality ones... VERY quality ones.

geowhitt · 10th June 2008, 10:37 PM

Hi thanks for the reply, i have changed all the caps i could see and even the 2 feedback caps,but i still get a noise when first switched on.
Like a buzzing arking then all goes quite?????
I have att a pic dont know if it would be of help.
Pic to big will have to sort it and post it later.

geowhitt · 10th June 2008, 10:48 PM

Is there anyone who can change the size of a file if i send it to them so i can put it on the page.

3rd June 2008, 05:22 PM	#1
geowhitt diyAudio Member Join Date: May 2008	Capacitor help Hi to all, this is my first post and its a help me sorry. I am going to re cap my moth power amps and i have found a shop that has most parts in stock, my problem is which caps to use. The caps fitted to the amps are samhwa 4700uf 63v and there is 2 others which are 470mFD 16v and 470uf 63v. My question is what is uf and mFD i have been told that 2 of the caps are feedback caps and have to be right i need to know what the parts are before i send a order off as i dont want to blow up the amps. Hope this makes sense

6th June 2008, 08:18 AM	#4
trodas diyAudio Member Join Date: Jun 2008	Another interesting thread (tough more specific about known bad caps and their replacement on voltage filtering circuits) are there: http://capsmod.net/forum/viewthread....extra=page%3D1 __________________ "It is dangerous to be right in matters on which the established authorities are wrong." - Voltaire ...just keep folding, just keep folding... my config

10th June 2008, 08:43 PM	#6
trodas diyAudio Member Join Date: Jun 2008	I would start replacing all the caps, becuase they are likely to be dried out already. 20 years can last only quality ones... VERY quality ones. __________________ "It is dangerous to be right in matters on which the established authorities are wrong." - Voltaire ...just keep folding, just keep folding... my config

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3rd June 2008, 05:41 PM	#2
Netlist diyAudio Moderator Join Date: Jan 2003	mFD is often used instead of µF. It's a source of confusion as mF is in fact milli(F) and uF or µ(F) is micro(F). So, both caps are most likely 470µF. A picture would give more certainty. Here's a nice page on capacitors: http://www.uoguelph.ca/~antoon/gadgets/caps/caps.html /Hugo

3rd June 2008, 06:07 PM	#3
geowhitt diyAudio Member Join Date: May 2008	Thanks for that,its like school again!!!!!!!! lots of reading. Thanks.

9th June 2008, 03:47 PM	#5
geowhitt diyAudio Member Join Date: May 2008	Thanks for the replys. I have changed the caps and the feedback caps,only to still have a small problem!!!!!. When i first switch the amps on i get a hum/buzz sound that last for a few seconds and the amps go quite and i then can use them. The noise is only there when first switched on. I thought the noise was a cap problem thats why i changed them and also there were 20yrs old. So i am at a loss now as to were to look on the amp for the problem. Any help please. The amps are Moth 100 watt mono amps.

10th June 2008, 10:37 PM	#7
geowhitt diyAudio Member Join Date: May 2008	Hi thanks for the reply, i have changed all the caps i could see and even the 2 feedback caps,but i still get a noise when first switched on. Like a buzzing arking then all goes quite????? I have att a pic dont know if it would be of help. Pic to big will have to sort it and post it later.

10th June 2008, 10:48 PM	#8
geowhitt diyAudio Member Join Date: May 2008	Is there anyone who can change the size of a file if i send it to them so i can put it on the page.

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