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).

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

 

[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]

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]

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]

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

 

[BrianDonegan]

Same problem?

http://www.diyaudio.com/forums/showthread.php?postid=795197#post795197

He had full mains voltage on the outputs of both channels, turned out to be a couple reversed caps.

 

[zafira1981]

Re: Same problem?

http://www.diyaudio.com/forums/showthread.php?postid=795197#post795197

He had full mains voltage on the outputs of both channels, turned out to be a couple reversed caps.

thanks!! i asked him what caps were reversed.

 

[billabong]

Nordic,

Nice pic of the loaded board. Thanks.

It will be useful when I start on my RevC boards. I'm close to finishing the case and the boards will follow. The case ended up being more work than I expected.

 

[zafira1981]

its working!!!!!!!!!!!!!!!!!!!

the problem was that R8 and R5 (22k 0,1%) were mistaken.
R8=22k
R5= 2,2k

now its working. i will test it with good speakers later.

thankssssssss

 

[Nordic]

lol, had a couple of incidents like that allready... in fact my first GC headache was exactly that.