Good morning guys, I have the JBL BP1200.1 amp giving some problems. When you turn it on from a cold power up the protection led is on then along with the power led relay clicks but the protection led will remain lit but the circuit rail voltages are still present.
Amidst that 43+/- on both rails and 12+/- on preamp you don't hear any immediate sound for about near a minute then you'll hear faint cracked audio and it gets clearer if you wait longer (protection led is still lit) after assuming the audio is sounding desirable, if you turn it off and on after the first long boot then the amp will work as expected until you turn it off for lengthy periods it's back to the same.
I'm thinking faulty condenser may be the issue but I don't know what section of the circuit to start troubleshoot.
Another thing I noticed also I have a 5amp power supply and if I increase the level control on the amp and the amp flagged my power supply all when I turn down the amp the amplifier power circuit doesn't recover back to 43volts it sits at 21volts audio is choppy and the output fets heats up rapidly.
Amidst that 43+/- on both rails and 12+/- on preamp you don't hear any immediate sound for about near a minute then you'll hear faint cracked audio and it gets clearer if you wait longer (protection led is still lit) after assuming the audio is sounding desirable, if you turn it off and on after the first long boot then the amp will work as expected until you turn it off for lengthy periods it's back to the same.
I'm thinking faulty condenser may be the issue but I don't know what section of the circuit to start troubleshoot.
Another thing I noticed also I have a 5amp power supply and if I increase the level control on the amp and the amp flagged my power supply all when I turn down the amp the amplifier power circuit doesn't recover back to 43volts it sits at 21volts audio is choppy and the output fets heats up rapidly.
It's not sufficient for this amp but I have previous instances with amps of this nature (actually same model amp) where it just turn on and play I couldnt go on a high gain level else it would get distorted and cropped out but my main curiosity is the no audio at initial power on.
I'll make some test tomorrow but first I'll try it on a larger power supply, I think I have a 20amp one that needs just a rectifier.
And a quick note, even when I remove the error amp (KIA393P) from the supply area and it's on with just the power led that first cold start, regardless of my audio input which is constant the level gain adjustment been adjusted doesn't maximize the audio just have to wait for it to "build-up" before I can hear it plays.
I'll make some test tomorrow but first I'll try it on a larger power supply, I think I have a 20amp one that needs just a rectifier.
And a quick note, even when I remove the error amp (KIA393P) from the supply area and it's on with just the power led that first cold start, regardless of my audio input which is constant the level gain adjustment been adjusted doesn't maximize the audio just have to wait for it to "build-up" before I can hear it plays.
Yes Mr Babin, audio is clean at pin one of the U103 IC.
I've add a pic but based on the cycles of the audio wave you may not recognize the pattern based on the music I was playing (I don't have a signal generator to feed a particular audio signal). But voltages as stated is 40+/- on rails but you can see in the pic it's on with bothe power and protection leds, and at this particular photo it's faint, choppy audio.
If there with it for about couple minutes it will come up and play, and play instant if I cycle the power, but if left for a long period then it's this "booting" again before I hear audio.
I've add a pic but based on the cycles of the audio wave you may not recognize the pattern based on the music I was playing (I don't have a signal generator to feed a particular audio signal). But voltages as stated is 40+/- on rails but you can see in the pic it's on with bothe power and protection leds, and at this particular photo it's faint, choppy audio.
If there with it for about couple minutes it will come up and play, and play instant if I cycle the power, but if left for a long period then it's this "booting" again before I hear audio.
Attachments
Read the following:
Basic Amplifier Repair (link to section on page)
The rail-rail oscillation will be on the drains of the output transistors.
Basic Amplifier Repair (link to section on page)
The rail-rail oscillation will be on the drains of the output transistors.
Good evening Mr Babin have read and reread but based on as illustrated it's an hard topic to explain, my thing is what reference point do I ground my probe and what setting do I set to take readings on my o scope?
Could it be a bad (or couple) caps as it performs after it seems to "charge up".
It's really a brainer as I only have a few minutes to make readings before it start performing, after that I have to wait a longtime for it to start hacked up again.
Could it be a bad (or couple) caps as it performs after it seems to "charge up".
It's really a brainer as I only have a few minutes to make readings before it start performing, after that I have to wait a longtime for it to start hacked up again.
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