Help: Boss CE-3800D "Static and whining noise"

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I purchased this amp non working and was told it was sent in for warranty repair's a month before it quit again. So I took it apart and found capacitor gut's all over the inside. They replaced all 6 of the 63v 1000uf's filters cap's and 3 input's and output transistors and didnt bother to clean up the mess left from the damage. Now I found most of the inputs and outputs fried so I have replaced them all, but now I am getting an high frequency pitch and static when amp kicks on. Would this be a bad inductor or possibly the driver board? :confused:
 

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high frequency pitch sound comes from toroid or inductor coil ?? if comes from toroid is not big deal, just add some silicone glue to firm the cooper wire loose, if it comes from inductor could be shorted or have an issue in the bridge driver board, another symptom of static noise or may be toroid's copper wire lost its insulating layer and making short circuit between them, have to inspect visually inductor and toroid.
 
That is what I thought, being a mono sub amp with low pass x-over, should not have high frequencies. Should I rewind inductor coil then?


maybe you should play the amp and try to touch the coil of the output inductor or move it a little, check if whinning reduces or increases. You will have an idea if this inductor has something to do in whinning.

Or if you have scope locate the frequency of the whinning sound compare it with the frequency of the power supply or of the driver board.
 
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Ok, I tried moving and tapping on the coil and it does cause the static or Hum to fade in and out, but it kinda does this all over the board. It seems like it gets quiet the closer i get my hand to the inductor and some other areas of the board. I think I will go ahead and re-wrap the inductor since I have everything anyway and I will report back what happens.
Thanks
 
That is what I thought, being a mono sub amp with low pass x-over, should not have high frequencies. Should I rewind inductor coil then?

Your problem is noise coming into the amplifier after the crossover. Probably in the power rails.

Do you have a CRO? Looking for HF content on the high voltage power rails will probably be informative. My guess is that the boost converter is having issues.
 
Your problem is noise coming into the amplifier after the crossover. Probably in the power rails.

Do you have a CRO? Looking for HF content on the high voltage power rails will probably be informative. My guess is that the boost converter is having issues.

Sorry, Not sure what a CRO is? I do have a 100mhz oscilloscope, just havent learned how to use them fully. If some can tell me what settings and where to put the probes, I will try.:eek:
 
Maybe you can do this,

First probe, put the positive lead of the CRO to +rail with black probe to GND and press the autosetup of the CRO.

Second probe, put the positive lead to speaker output and compare the waveform of the two signals.

Upload the screen shot of your CRO here...
 
Maybe you can do this,

First probe, put the positive lead of the CRO to +rail with black probe to GND and press the autosetup of the CRO.

Second probe, put the positive lead to speaker output and compare the waveform of the two signals.

Upload the screen shot of your CRO here...

Ok, Just replaced my CRO, I had an HP 54501A digital 100mhz that I just couldnt figure out and get it to function the way it should. It's for sale now. lol Anyways here are some pics from the new setup auto measuring high voltage rail on number 1 probe and speaker positive on 2nd probe. Measuring A/C.
 

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Here is a sound file of the static noise from this amp. Anybody have any ideas what I should try next?

Well, I tried to upload a zip file of the sound but apparently it wont let me. If anybody can tell me how to upload sound files, I will try again.
 
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Well, you have a serious power supply problem, there's about 10V of crap coming through at ~100kHz. Given the asymmetry of the the waveform, I'm going to guess that the fault is with the latter part of the PSU switcher, i.e. after the switching transformer. I could be totally wrong here, but have a look for shorts (due to gunk from the exploded caps) and bad/open/shorted components (diodes, capacitors) in the rectifier+filter stages of the PSU.
 
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