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Old 21st December 2005, 10:44 PM   #1
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Unhappy cant make it work: mauro penasa rev 1

hi!!! i've made the REV1 and cant find out what is wrong. I'm getting -V at output.

i measured the +v,-v, GND of LM3886 and +v, -v of lm318 and the values are OK.

anyone else had this problem?
here some pics:
(i know it's ugly, it's just a test).

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Old 22nd December 2005, 08:13 AM   #2
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better fix the heatsinks first

Gajanan Phadte
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Old 22nd December 2005, 11:47 AM   #3
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yes, today i will put a heatsink.

there is something i didnt say...

I'm using it with an external power supply of 2x25V DC. so that's why i didnt put the big caps & bridge. I'm testing each channel without the DC protection. Both channels didnt work.
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Old 22nd December 2005, 12:04 PM   #4
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How about the MUTE pin? Connected to anything? No inputs are floating (unconnected)?
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Old 22nd December 2005, 12:09 PM   #5
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Quote:
Originally posted by peranders
How about the MUTE pin? Connected to anything? No inputs are floating (unconnected)?

MUTE is connected to -V trough a 33K resistor.

mmm i think that there is no input floating, but i will double-check. what is strange to me is that both channels are doing the same think, -V at output.

thanks
Jorge.
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Old 22nd December 2005, 02:48 PM   #6
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My best guesses are:

- A component mounted between the wrong two holes (on both sides)

- A solder bridge jumping tracks (hard to see in pic, but there are several very close tracks on the layout)

- Fried 3886s (less likely I suppose, but possible)
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Old 22nd December 2005, 03:23 PM   #7
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Quote:
Originally posted by BrianDonegan
My best guesses are:

- A component mounted between the wrong two holes (on both sides)

- A solder bridge jumping tracks (hard to see in pic, but there are several very close tracks on the layout)

- Fried 3886s (less likely I suppose, but possible)
i will check as soon as i can. the first option sounds possible. the first, i checked for jumping tracks, and the third, fried 3886, its possible but they were brand new.

thanks!
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Old 22nd December 2005, 03:29 PM   #8
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I have accidently put components between the wrong holes before. I usually print out the component locations, then draw them in by hand before mounting components now (or use toner transfer and print then right in the board). I kind of like the look of the hand-drawn components though.
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Old 22nd December 2005, 03:32 PM   #9
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Quote:
Originally posted by BrianDonegan
I have accidently put components between the wrong holes before. I usually print out the component locations, then draw them in by hand before mounting components now (or use toner transfer and print then right in the board). I kind of like the look of the hand-drawn components though.
great idea, i will start doing it!!! i mean to hand-write the component layout.
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Old 22nd December 2005, 03:50 PM   #10
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Ok then I don't feel so anal...

Here is my REV C pic for those who would like it...
Brown parts = PSU
RED = Gain stage
Yellow = Softstart
Blue = amp
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