Hi there guys 😀
Good evening,
Got a defect Audio System F2-500 amplifier, where I'm struggling on for 2 months already.
I've tried several things, but unfortunately I could not find the possible cause of the problem. It has 2 problems.
Problem 1
From left to right, bank 2, 3 and 4 has a potential difference between the Gate and the Source (pin 1 and 3). I fixed the left bank 1, it had bad BCP53 transistors and BC850c and 860c.
On pin 1 and 3 from the output fets (FQP22p10 and FQP33n10) should be the same negative or positive rail voltage. When I installed the fets it went in protect. When the potential difference is gone it doesn't go in protect.
This is a problem, but hopefully I would be able to fix this problem myself after problem 2 has been fixed.
Problem 2
I'm really struggling on this one.
Bank 1 and 2 has absolutely no audio input to the gate of the output fets.
Bank 3 has a sound wave on the gate but the amplitude is 3x smaller than the amplitude from the RCA itself.
Bank 4 has a sound wave on the gate with an amplitude around 10x smaller than the amplitude from the RCA itself.
Photo 1: This is the overview of the amplifier itself. 4 banks of output fets (2 banks per channel)
Photo 2, 3: Photo 2 is the Source of the fets which has the rail voltage you see on photo 3
Photo 4: This is the gate of the fets which should have the same voltage as the Source on photo 3
Photo 5, 6: Here you see the gate of bank 3 with a 100Hz sine wave (3x smaller than the RCA signal)
Photo 7, 8: Here you see the gate of bank 4 with a 100Hz sine wave (approximatelly 10x smaller than the RCA signal)
I replaced all the BCP56, BCP53, BC850c and BC860c transistors from all the 4 banks, I checked all the resistors per bank if they are within tolerance and they are.
Does anyone has an idea?
Thank you very very much for every bit of help!!!! 😀
Good evening,
Got a defect Audio System F2-500 amplifier, where I'm struggling on for 2 months already.
I've tried several things, but unfortunately I could not find the possible cause of the problem. It has 2 problems.
Problem 1
From left to right, bank 2, 3 and 4 has a potential difference between the Gate and the Source (pin 1 and 3). I fixed the left bank 1, it had bad BCP53 transistors and BC850c and 860c.
On pin 1 and 3 from the output fets (FQP22p10 and FQP33n10) should be the same negative or positive rail voltage. When I installed the fets it went in protect. When the potential difference is gone it doesn't go in protect.
This is a problem, but hopefully I would be able to fix this problem myself after problem 2 has been fixed.
Problem 2
I'm really struggling on this one.
Bank 1 and 2 has absolutely no audio input to the gate of the output fets.
Bank 3 has a sound wave on the gate but the amplitude is 3x smaller than the amplitude from the RCA itself.
Bank 4 has a sound wave on the gate with an amplitude around 10x smaller than the amplitude from the RCA itself.
Photo 1: This is the overview of the amplifier itself. 4 banks of output fets (2 banks per channel)
Photo 2, 3: Photo 2 is the Source of the fets which has the rail voltage you see on photo 3
Photo 4: This is the gate of the fets which should have the same voltage as the Source on photo 3
Photo 5, 6: Here you see the gate of bank 3 with a 100Hz sine wave (3x smaller than the RCA signal)
Photo 7, 8: Here you see the gate of bank 4 with a 100Hz sine wave (approximatelly 10x smaller than the RCA signal)
I replaced all the BCP56, BCP53, BC850c and BC860c transistors from all the 4 banks, I checked all the resistors per bank if they are within tolerance and they are.
Does anyone has an idea?
Thank you very very much for every bit of help!!!! 😀
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The potentiometers look really dirty.
I have a f4-600 I'm working on so if you need values of anything i can try to help on that otherwise I'm too inexperienced yet to give more insight.
I have a f4-600 I'm working on so if you need values of anything i can try to help on that otherwise I'm too inexperienced yet to give more insight.
After such a long time working on a amp, sometimes you lost track...
So what was not working the first time you tested the amp?
Just one channel was broken, or more and why did you remove all mosfets from all channels?
Were the driver transistors you replaced defective?
I did repair some Twisters in the past, most of the time there was something wrong with the bias voltages, see the diagram F2-190 (+BIAS and -BIAS from the power supply).
So what was not working the first time you tested the amp?
Just one channel was broken, or more and why did you remove all mosfets from all channels?
Were the driver transistors you replaced defective?
I did repair some Twisters in the past, most of the time there was something wrong with the bias voltages, see the diagram F2-190 (+BIAS and -BIAS from the power supply).
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Hey Bert,
Seems like I am not the only person with this problem 😀, this is what happens to me now XD
The reason why I removed all the output fets is because this amplifier always went into protect. It was not possible to measure anything, so I took out the rectifiers and saw the power supply was working fine. So I removed the output fets and discovered a potential difference to the Gate and the Source. That is the reason why it gets into protect.
The driver transistors from the first bank were defective and that fixed the Potential difference between the Gate and the Source from bank 1. From the other 3 banks, replacing the transistors did not solve the problem.
The hardest problem from this amplifier is the fact that it does not forward any audio sine waves to the first 2 banks, and different but REALLY low amplitude sine waves to bank 3 and 4.
Thanks for the help DanFS722, if I need some information I will let you know 🙂
Seems like I am not the only person with this problem 😀, this is what happens to me now XD
The reason why I removed all the output fets is because this amplifier always went into protect. It was not possible to measure anything, so I took out the rectifiers and saw the power supply was working fine. So I removed the output fets and discovered a potential difference to the Gate and the Source. That is the reason why it gets into protect.
The driver transistors from the first bank were defective and that fixed the Potential difference between the Gate and the Source from bank 1. From the other 3 banks, replacing the transistors did not solve the problem.
The hardest problem from this amplifier is the fact that it does not forward any audio sine waves to the first 2 banks, and different but REALLY low amplitude sine waves to bank 3 and 4.
Thanks for the help DanFS722, if I need some information I will let you know 🙂
Usually not all 4 channels are defective, most of the amps have 1 or 2 channels (from bridged) defect. So thats's why I remove them (output transistors/ mosfets) channel by channel to pinpoint which channel cause the protection.
And then measure all the Vdc on the drivers, opamps 5532 are correct.
And then measure all the Vdc on the drivers, opamps 5532 are correct.
Is one channel driving a pulse of DC to the output when the amp initially powers up?
Are you applying B+ and remote at the same time or do you connect B+ and ground and THEN apply remote (after a brief delay)?
It's very difficult to use voltage to troubleshoot the output stage of an amplifier with the outputs out of the circuit because it leaves the feedback loop open.
Are you applying B+ and remote at the same time or do you connect B+ and ground and THEN apply remote (after a brief delay)?
It's very difficult to use voltage to troubleshoot the output stage of an amplifier with the outputs out of the circuit because it leaves the feedback loop open.
Hi, sorry to bump up your thread but is no point to start a new one. Got a F2 500 MKII with quite the same problem. Powers up but no sound, i have no idea about electronics and how to work on them but i'm trying. In my opinion this amp shouldn't turn on but who knows i'm not a specialist.
From what i can check the power side mosfets (75333P) are all shorted and 1 gate resistor is gone but not sure about this because i don't know how to proper check, used the multimeter on resistor setting on R3-R10 and they vary between 14.3-19.2 when reading and one is 56.4 next i'm trying to find out how to check the rectifiers D1-D4
I've start looking for new mosfets and the closest similarity i find with HUF75333P are FQP65N06 if you know some better equivalent for the mosfets let me know please.
Hope i don't sound like an idiot for what i've just said, peace
From what i can check the power side mosfets (75333P) are all shorted and 1 gate resistor is gone but not sure about this because i don't know how to proper check, used the multimeter on resistor setting on R3-R10 and they vary between 14.3-19.2 when reading and one is 56.4 next i'm trying to find out how to check the rectifiers D1-D4
I've start looking for new mosfets and the closest similarity i find with HUF75333P are FQP65N06 if you know some better equivalent for the mosfets let me know please.
Hope i don't sound like an idiot for what i've just said, peace
Please don't post in a repair thread that was started by someone else unless you are trying to help them.
Start a new thread if you need help with a repair of your own.
http://www.bcae1.com/temp/newthreaddiy01.png
Start a new thread if you need help with a repair of your own.
http://www.bcae1.com/temp/newthreaddiy01.png