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Old 21st June 2008, 07:27 PM   #1
kanifee is offline kanifee  United Kingdom
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Default Chip amp lm3886 help needed!!!

Hi all, had my gainclone chipamp.com amp sitting waiting for a tranny for a while now, managed to get one the other day and came across a chasis to test it in aswell.
I set about mocking everything up and turnd it on for the first time.... nothing, the led doesnt light up atall and as far as i can tell its dead as a door nail, what id like is advice on how to start troubleshooting, im a bit of a novice and dont really know were to start, the tranny i got was a 230v 2x25v secondry @4.5a.
any help would be greatly appreaciated, ive checked over everything and it all looks fine, soldering looks spot on, only thing im unsure of and this maye make me sound like a complete **** in these forums is the 0.1uf 63v - BC polypropylene capacitors, im unsure how to gauge there polarity if they have a specified one on the pcb, i couldnt tell at the time if they needed a certain orientation and the pcb never stated 'any, neither did the schimatics, sorry if im a little noobish this is my first venture and im still finding my legs.

I dont have a source or speakers connected up yet i just wanted to see if it would fire up to start with.

Heres a link to the schimatics http://chipamp.com/docs/lm3886-manual.pdf
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Old 21st June 2008, 07:31 PM   #2
PSz. is offline PSz.  United States
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Did you put the led in backwards?

Those film caps are non-polar.

best regards,
psz.
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Old 21st June 2008, 07:32 PM   #3
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The cap is non-polar... no worries.
Do you have a Meter? Have you checked PSU ? Before hooking it up to amp circuit and after?


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Old 21st June 2008, 07:34 PM   #4
kanifee is offline kanifee  United Kingdom
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Hi yes i have a meter, havnt checkd it before and after being hooked to the amp, ill remove the amp modules and test it now, whats the best way to test the power supply/what should i be reading from it in regards to voltage!

edit*** yes the led seem to be on correct
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Old 21st June 2008, 07:50 PM   #5
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I suggest that in the future, you check builds in stages.
Test the Transformer ~ 25VAC
Test PSU after filter caps ~ +/-35 VDC or 70 VDC rail to rail


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Old 23rd June 2008, 07:26 PM   #6
kanifee is offline kanifee  United Kingdom
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Well today i orderd my new lm3886 chip and replacemant caps for the ones i poped, really happy with the sound though only have one channel untill the other is repaird and refitted; one thing i have noticed is int he odd song with really deep havy bass the lighter tones seem to fade away as the bass comes in and then re emerge as the bass disipates what is this?

Secondly what sort of improvemants can i start making, new componants i can add and what would these effect in the sound quality?
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Old 23rd June 2008, 07:32 PM   #7
Nuuk is offline Nuuk  United Kingdom
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Quote:
one thing i have noticed is int he odd song with really deep havy bass the lighter tones seem to fade away as the bass comes in and then re emerge as the bass disipates what is this?
Just a guess but it could be playing a stereo signal through a mono system. I would wait till you have both channels working before making any assessments!
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Old 23rd June 2008, 09:01 PM   #8
kanifee is offline kanifee  United Kingdom
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sounds advice lol
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