cant make it work: mauro penasa rev 1

[zafira1981]

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).

[gmphadte]

better fix the heatsinks first

Gajanan Phadte

[zafira1981]

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.

[peranders]

How about the MUTE pin? Connected to anything? No inputs are floating (unconnected)?

[zafira1981]

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.

[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)

[zafira1981]

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!

[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.

[zafira1981]

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.

[Nordic]

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