Fortè Audio 1a

[Michele]

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]

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]

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]

. . . 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]

tested ,somewhere from net

 

[Nelson Pass]

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]

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]

mea (maxima) culpa!

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]

 

[jh6you]

Using the leftover, I'll try this for my F1.

Regards
jH

 

[jh6you]

I tried the above dc-blocker, but with 6,800uF/25V (small physical size) instead of the planned 10,000uF/50V. I arranged them for both F1 and BOSOZ.

When I turned on F1 and connected to J-Low (no others), about 90% of the buzz has gone from the transformer of F1 and the speakers. I could hear the very weak buzz when I brought my ear 50mm close to them. And, I connected all system and heard that the sound was cleaner, particularly with voices.

I had some experience of explosion of electrolytic capacitors. In general, I am very much afraid of using them whenever the use is related with over-voltage and reverse-voltage application. Nevertheless, they have been working well for continuous 6 hours. They were not getting hot. This means I might be no need to worry about another potential explosion hazard.

O . . . sorry for having interrupted the thread . . .

By the way, I expect that they will work also for Forte 1a.

Regards
jH

 

[jh6you]

Hi Choky

It seems that your circuit on the post #9 must have cap of big enough voltage rating. Otherwise, might BUMB !!!

Regards
jH

 

[Zen Mod]

Hi Choky

It seems that your circuit on the post #9 must have cap of big enough voltage rating. Otherwise, might BUMB !!!

Regards
jH

just for voltage sag on 100 ohms ?

another one.... didn't checked,and didn't looked too much

 

[jh6you]

Hi Choky

Thanks for the circuit.
By the way, I will create a new thread regarding the dc-blocker.

Regards
jH

 

[djk]

From the Bryston 3B

http://www.diyaudio.com/forums/attachment.php?postid=328821

 

[Michele]

As I said, I have 2 Fortè Audio. 1 uses 4 International Capacitors caps, and the other 4 Audiovox caps, Is anybody able to say why?

 

[Zen Mod]

certainly not sonical reasons

ya hear ever for market ?

 

[Nelson Pass]

As I said, I have 2 Fortè Audio. 1 uses 4 International Capacitors caps, and the other 4 Audiovox caps, Is anybody able to say why?

I speculate that the Audiovox were put in after-market.

 

[Michele]

You are the best Nelson, I hope to see you when you will be in Italy