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Old 24th February 2006, 01:01 PM   #1
sith is offline sith  Croatia
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Default chipamp PSU problem, need help

Hi there, I already asked question on ChipAmps forum , but nobody seems to know how to solve problem...

Just finished, PA100, chipamp and snuberized regulated PSU.

Testing one chanel (board) everything is beautiful, rail voltage is steady +/-27V, dc-offset 15mV, testing other the same thing... Absolutely beautiful...

Now the funny part, when I connected both channels(boards) to a PSU I got massive voltage drop and negative LM388 got too hot to touch... I used a single power tranny (separate windings), a single PSU, two rectifiers (ready made, rated 7A) LM388 regulators... So, every board works perfectly, but when they are both in system sh.. hits the fan...

Alexw amp.
http://shine7.com/audio/pa100.htm

Regulated psu , nuuk's pages http://myweb.tiscali.co.uk/nuukspot...gainclone6.html
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Old 26th February 2006, 03:14 PM   #2
Leolabs is offline Leolabs  Malaysia
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Did you test each board separately???
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Old 26th February 2006, 06:22 PM   #3
sith is offline sith  Croatia
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Did you test each board separately???
Yes, each board works perfectly, but when they r connected together they don't work...

I want to try 'classic' PSU (no regulators, just cappacitors) but I get +/- 38 volts at rails, is that too much for 3886 (2x2 per channel)???
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Old 26th February 2006, 06:55 PM   #4
Bazukaz is offline Bazukaz  Lithuania
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LM3886 does not need a regulated power supply.Feel free to try +-38 volts(These chips can handle +-42V).However , continous operation at +-38 Volts is only considerable if your loadspeaker impedance is >=8 ohms.LM3886's has an unique Spike protection , which is annoying when turns on , but keeps output transistor array in safe temperature range.

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Lukas.
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Old 1st March 2006, 06:35 AM   #5
sith is offline sith  Croatia
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Just tryed 'classic' (unregulated) PSU everything worked perfectly

Funny thing, regulated PSU works with 3775
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Old 1st March 2006, 06:47 AM   #6
Nordic is offline Nordic  South Africa
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Just how much current can that regulator deliver?
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Old 1st March 2006, 08:24 AM   #7
sith is offline sith  Croatia
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Just how much current can that regulator deliver?
5A peak 12.... according LM338 datasheet
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Old 1st March 2006, 10:19 AM   #8
Nordic is offline Nordic  South Africa
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Yeah, thats plenty, and did you add the caps as per the datasheet for stability etc...?

Also as per usual with error checking new stuff, grab your multimeter and check every single resistor!

Good luck.
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Old 2nd March 2006, 12:11 PM   #9
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sith, Are you monster/shine7? or did you buy his PCBs? Or did you fabricate the pcbs?

Afraid I can't help with your problem, just interested in the above.
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Old 3rd March 2006, 06:22 AM   #10
sith is offline sith  Croatia
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sith, Are you monster/shine7? or did you buy his PCBs? Or did you fabricate the pcbs?
no Monster/Shine7 is AlexW from forum here, and no i didn't buy PCB , just did plain old p2p using euro board...
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