Forte model 3

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4krow

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Joined 2011
I intended to do the right thing by replacing the old power supply caps in my model 3 amp. What I found were some caps that are much bigger in value and size, and voltage. The originals are 24,000 with a 60 volt surge rating. The new ones are 37,000 with a rating of 100V. After replacing the caps, the amp immediately blew the 8 amp main fuse. I then put a 6 amp current limiter in the incoming AC line after the fuse. It still blows the main fuse. I am thinking that I would be better off just getting 24,000 uf caps of the same voltage rating and calling it good. Any thoughts?
 
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4krow

Member
Joined 2011
"Unless your new capacitors were installed incorrectly (or are bogus), they are not what is blowing the line fuse."

I do agree with your assessment. Think that I might take a second look. Just didn't think that there would be a huge increase in inrush current. Thanks for the thought.
 
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4krow

Member
Joined 2011
PICS

Yah, I almost for got the pics. I can get a better P5180034.jpg close up if that helps.
 
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4krow

Member
Joined 2011
Gary,

I reversed the polarity (just like Kirk did on Star Trek against Scotty's wish), and it works. "My Creature Has LIFE! The transistors are running about 113 F on both sides. Now, just to check, the current limiting device is cooking at 260 F. That sounds a little warm to me. It is rated at 6 amps. Should get a bigger one or just take it out all together?
 
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gary s

Member
Joined 2002
I think Nelson likes to run heatsink temps for class A amps at around 50 to 55 deg c so 113 F (45 deg C)is a bit low, Check the biasing as per instructions and maybe the current limiting device is faulty or the wrong type. I assume you have all the schematics and biasing instructions for this amp.
 
4

4krow

Member
Joined 2011
Gary,

Thanks for the info. The amp is actually running class A/B at 200 WPC, so I am thinking that the temp may be good. As far as schematics/service manual, I would really like to find either! If you know where I could get my hands on such, let me know.
Maybe I will try another step up for a current limiter, like 8 amp. or so. If that doesn't work, I may just take it out of circuit.

Greg
 
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LouieTheG

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Joined 2015
Forte Model 3 conversion to Model 1a

I have a Forte Model 1a and Model 3. I'd like to convert the Model 3 to be identical to the Model 1a, Class A, 50wpc @ 8ohm. Can anyone offer me some help in doing this conversion? I'm told the two amps are identical except for power supply ground plane and bias setting.
 
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