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Forte Model 3 Bias
Forte Model 3 Bias
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Old 8th March 2013, 02:35 AM   #1
Zero Cool is offline Zero Cool  United States
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Default Forte Model 3 Bias

I have a Forte Model 3 on my bench that has bad Bias trimmers, I replaced them with 20 turn pots as everything i have read says the bias is very touchy. this definitely made the bias much easier to precisely adjust BUT, the Owners/Service manual states 70mv across the .47 ohm emitter resistors. but at 45-50mv after 20 minutes the heatsinks are both at 50deg C! I didn't dare push it past that point without getting some clarification.

Any advice?


Zc
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Old 10th March 2013, 09:16 PM   #2
Zero Cool is offline Zero Cool  United States
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I figured SOMEBODY would have something to say?? I can't imagine this thing running at 70mv of bias, it would be way too hot I think??

the sinks run at 50deg C now. was this amp supposed to run hotter than that?


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Old 10th March 2013, 09:19 PM   #3
Zen Mod is offline Zen Mod  Serbia
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Forte Model 3 Bias
if thingie is having anything with Pa , you know that 45-50C is magic figure ...... more than exact Iq value
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Old 28th April 2013, 09:44 AM   #4
RobertS61 is offline RobertS61  Netherlands
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Zen Mod is right as usual.
NP did not find my 56 degrees with my SA/1's any problem.
Fifty degrees Celcius is just fine.
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Old 26th December 2017, 06:06 PM   #5
Badbrad is offline Badbrad
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I have a model 3 running very cool as well. I'm ready to rebias it but would love a bit of help. Does anyone have a schematic of a model 3 or is willing to help a bit. Have meters, a digital scope & ready to go... just want to be careful.
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Old 26th December 2017, 06:14 PM   #6
cumbb is offline cumbb
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No problem to run these amps with lower bias. As you like;-)
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Old 26th December 2017, 06:38 PM   #7
Nelson Pass is offline Nelson Pass  United States
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Forte Model 3 Bias
As posted reply to Pass Labs thread, the Model 3 schematic is virtually identical
to the model 1, mostly supply and bias difference.
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Old 26th December 2017, 06:40 PM   #8
cumbb is offline cumbb
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Forté Audio Model 3: caps and schematics?

Forté Audio Model 3: caps and schematics?
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Old 26th December 2017, 08:09 PM   #9
Badbrad is offline Badbrad
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Thank you Mr. Pass. I just wanted to make extra sure I didn't let the smoke out of my Forte. I have no spare amplifiers kicking around right now.
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Old 30th December 2017, 04:17 PM   #10
Badbrad is offline Badbrad
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OK Forte lovers and audiophiles. Can anyone give me a scientific, not an artsy answer to the differences I should hear running my Forte Model 3 with high or low bias voltages? I listen on a set of Magneplaner 1.7is with a REL T9i sub. Thanks in advance.
 

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