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Old 22nd May 2008, 10:52 AM   #1
st2_998 is offline st2_998  Italy
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Default Forté Audio Model 3: caps and schematics?

I'm very satistfied of my new old amp!

Due to its age, I was considering a power supply recapping, I'm pretty sure someone worked on it and can give me some valuable advice

And... where can I find the schematics? I took a glance to Model 1's one but the PS appears to be wired in a different way.

Thanks everybody for dropping opinions and help.
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Old 23rd May 2008, 02:22 AM   #2
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It's pretty much the same. Higher voltage, lower bias.
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Old 23rd May 2008, 02:03 PM   #3
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I was thinking about swapping the two caps in series for each supply branch with one only (47.000 uF 100Vdc instead of 2x 24000 uF 65 Vdc, total Vdc present is 76 Vdc), leaving the secondaries' center taps unconnected (insulated). Possibily 10 uF poly bypass on each.
Is all that a bad idea?
Thanks.
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Old 24th May 2008, 07:14 PM   #4
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I think the amp uses those center taps to establish ground. You
would probably get some undesirable results if that's the case.
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Old 24th May 2008, 08:33 PM   #5
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I believe this is surely true for the 1A, as far as I can understand from the schematics. Unfortunately I don't have the schematics for the 3A power supply, but in the amp it seems that ground (a star center) is tied to one each of the secondaries' outputs (one +, one -), center taps end inbetween the two series supply caps and nothing is connected to them except power LED.
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Old 24th May 2008, 11:28 PM   #6
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Quote:
was thinking about swapping the two caps in series for each supply branch with one only (47.000 uF 100Vdc instead of 2x 24000 uF 65 Vdc, total Vdc present is 76 Vdc), leaving the secondaries' center taps unconnected (insulated). Possibily 10 uF poly bypass on each.
I recently opened up a Forte for a friend of mine. I believe it was a 3a. (did they make it up to 7a?)

If you can post a picture of the inside, I could provide some better comments (if its the same ps).


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Old 25th May 2008, 01:09 PM   #7
st2_998 is offline st2_998  Italy
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Here's a schematic of the Forté Model 1A power supply

Click the image to open in full size.

here is how it looks like (to me!) in the Model 3 I own

Click the image to open in full size.

I'll post pics asap, thanks
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Old 25th May 2008, 11:35 PM   #8
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Looks right. I saw some old usenet postings that led me to
turned my Forte 3 into a 1 -- I only had to reroute the wires.
Now completely class A -- sounds better.
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Old 26th May 2008, 06:48 PM   #9
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Here are the pics
Click the image to open in full size.
Click the image to open in full size.

Blue connected to ground (busbar)
Red connected to rectifier bridge and supply fuses to the channel boards
Orange should be center tap
It appears that using one cap instead of two could be possibile, center tap has to be disconnected but that shouldn't cause problems.
Is that right?
Thanks
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Old 29th May 2008, 12:32 AM   #10
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Clearly that is different than the amp I worked on.

I wouldn't hazard to try to advise you on something I haven't done. If you don't mind the possibility of letting all the magic smoke out of your amp, then forge ahead with the PS re-do.

Otherwise, replacement in kind is always a safe way to go.

Good luck!

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