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-   -   Fortè Audio 1a (http://www.diyaudio.com/forums/pass-labs/68736-forte-audio-1a.html)

Michele 28th November 2005 01:05 PM

Fortè Audio 1a
 
I have a problem with 1 of the 2 Fortè Audio I have. Sometimes the transformer make a noise (a sort of zzzzzzz), must I change it or can I make something else? Thank you

needtubes 28th November 2005 03:27 PM

I picked up a Forte 1A not long ago and have also noticed that the transformer buzzes/hums. It is fairly loud when first switched on, but settles to a lower volume after a second or two. I don't think this is anything to worry about, but someone else may have a more decisive opinion on this.

Nelson Pass 29th November 2005 02:21 AM

Like most other toroids, the transformer hates DC on the line.
Try running it with a large capacitor in series with the line. I
usually use two big electrolytics back to back (say + to +)
with a power diode across each one to keep them from getting
too much reverse bias.

jh6you 29th November 2005 01:07 PM

Quote:

Originally posted by Nelson Pass

. . . large capacitor . . .
. . . reverse bias . . .


Hi, Nelson

After having moved to a new apartment recently, I get somewhat DC from the wall AC power.

1. How large is large . . . ? 1,000uF or 10,000uF?
2. Is the small reverse bias to avoid the re-anodizing problem?

Thanks.

Regards
jH

Zen Mod 29th November 2005 02:01 PM

2 Attachment(s)
tested ,somewhere from net

Nelson Pass 29th November 2005 06:48 PM

I think you need to reverse the diodes (or the polarity
of the caps) in that diagram. Also, it's wise to place a
bleed resistor, say 100 ohms @ 3w or so, across the diodes.

jh6you 29th November 2005 08:41 PM

Now I clearly understand why the voltage rating of the cap doesn't matter. Choky's diagram provides too much reverse bias. :)

Regards
jH

Zen Mod 29th November 2005 08:57 PM

mea (maxima) culpa!:cool:

hehe-when I tested that circ,I didn't have schmtic near me,and made it right from my scull.......
obviously -in right way-but I didn't double checked that pic........

Zen Mod 29th November 2005 09:06 PM

2 Attachment(s)
:clown:

jh6you 29th November 2005 10:02 PM

2 Attachment(s)
Using the leftover, I'll try this for my F1. :)

Regards
jH


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