Bluewater, have you confirmed that both pots are at zero and re started the bias process from scratch?
thank you for all the reply's.
no I haven't tried starting from zero mostly because it was working fine before this happened. I not sure if starting with the pots is the right course just yet.
tinitus, what do you mean by sticks?
no I haven't tried starting from zero mostly because it was working fine before this happened. I not sure if starting with the pots is the right course just yet.
tinitus, what do you mean by sticks?
Oh, sorry
I wrote "prove" sticks, and it should have been "probe" sticks
Those things to connect multimeter to amp board
Isnt that what they are called?
What I was asking
Do you measure the right way?
Is multimeter used properly?
Connection point, meter setting etc.
Are your probe sticks in good condition?
I have to resolder mine frequently
Not the most reliable things
And sometimes a meter works fine with one setting and not with some other setting, cheap ones ofcourse, but thats what most of us can afford, but may not be completely reliable either
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they work fine and are in good shape. When adjusting the dc offset I connected them to the output and the output ground.
I dont think you should do that without monitoring bias at the same time
As I understand it, its possible to "find" a bias a point where DC is low
But you cannot just turn bias pot to the lowest DC
It should be done carefully, bit by bit
And never turn bias pot only looking at DC
Output devices can go dead in a second without heatsink even getting hot
But now I talk about something Im not sure about, as I havent built my F5 yet
But I do remember to have done something similar, turning a trim pot without anything happening
Amp went dead before I realised I had been looking at the wrong meter setting
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While adjusting the offset I had another multimeter monitoring the voltage drop on r11 or r12.
I usually turn the bias down to zero first then set the DC offset before attaching a speaker.
Then I put a multimeter across a source/emitter resistor and set it to just get rid of crossover distortion on the scope which is usually around 5mV across 0r22 resistors.
If its a new design i would then put a household iron on the heatsink and make sure the bias doesnt do anything silly as the ehatsink heats up.
My other channel (right) is working great. The one that is having the problem (left channel) was working great. It actually sound better the other (right) channel. I'm not sure but where all the values were 2.2k they were brought up to 2.21k ohms.
Anyways I'm wondering if there is a way to trouble shoot my problem. I can turn it on with the input isolated and doesn't seem to hurt anything. Is there a way to check for voltage drops to find out if the jfets are causing the issue or could it even be part of what is causing my problem?
Anyways I'm wondering if there is a way to trouble shoot my problem. I can turn it on with the input isolated and doesn't seem to hurt anything. Is there a way to check for voltage drops to find out if the jfets are causing the issue or could it even be part of what is causing my problem?
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Just read the F5 manual
You get zero DC when both bias trimpots are balanced
If you have DC problems, I suppose one half/side is not right
Or you may have very poorly matched Jfets
Or maybe too much heat from your soldering
Even if you think your soldering is perfect, you might be surpriced if you look through a magnifying glass
Or you may find a small bit of solder waste making a shorting
I check ALL my solder joints carefully with magnifying glass, and proper light
Just a thought
You get zero DC when both bias trimpots are balanced
If you have DC problems, I suppose one half/side is not right
Or you may have very poorly matched Jfets
Or maybe too much heat from your soldering
Even if you think your soldering is perfect, you might be surpriced if you look through a magnifying glass
Or you may find a small bit of solder waste making a shorting
I check ALL my solder joints carefully with magnifying glass, and proper light
Just a thought
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i have a problem guys. i need to the data sheet of my f4-1600 4 channels... my firend had it and it blowed a transistor, he took all of them off and to use it for parts... now i have it and need to change all of the transistors can any of u help me??
Oye Joselito,
este forum es para los amplificadores caseros de Nelson Pass, no para esos en coches, este de usted es un amplificador del coche.
este forum es para los amplificadores caseros de Nelson Pass, no para esos en coches, este de usted es un amplificador del coche.
F5
Hi Jacco, dejate de eso hombre 😉 Help hem even met zijn F4 😉
Back to topic.
"Bleuwater"
Perhaps one of the output transistors is tighter than the other? That way you'll have a difference in cooling the device which will give you DC offset.
Just my 2 cents.
Best regards,
Audiofanatic 😉
Hi Jacco, dejate de eso hombre 😉 Help hem even met zijn F4 😉
Back to topic.
"Bleuwater"
Perhaps one of the output transistors is tighter than the other? That way you'll have a difference in cooling the device which will give you DC offset.
Just my 2 cents.
Best regards,
Audiofanatic 😉
Hi ZM
Please excuse me if this is a silly question, but can the mosfets share the gate (R13&R14) and source resistors (R11&R12) or do they each need their own? I was planning on trying other variations (i.e. 20R/100R feedback) but NP's comment has intrigued me.🙂