[Mizu]

Hey guys,

Some months ago I dropped the idea of completing my Mini3, due to a problem in the sound output. From all songs I heard there is reverb in voices, and they seems "farther" than normal. Amb asked to check L1G and U4 and every resistances between them, Which I did. relowed everything.. but still nothing. Even reflowed output pads.

I haven't found anybody with this particular problem, so i'm asking here..

Should I replace U4 ?

Thanks !

 

[MisterX]

Do you remember what the DC offset is for the ground channel?

 

[Mizu]

My meter set to 2V at DCV, i'm getting this reading :

IG -> OG = 1.27
IG -> OL = 0.003
IG -> OR = 0.004

Seeing that proves me that

1: I may have cold joints or bridge, which i'm sure I don't
2: U4 might be blown ?

 

[MisterX]

1: and or a wrong resistor value
2: A fried U4 looks like a reasonable assumption to me.

 

[Mizu]

Ouch they are so fragile ! U5 also blewn out at start.. Guess i'll have to replace U4 then.. fortunately I have a U4 in hand. I hope I won't break the circuit when i'll unsolder it.

Thanks for your input !

 

[MisterX]

I would just cut it off, it's a little safer to remove the remaining bits one at a time then it is to try to remove the op-amp by heating all of the pads at the same time
(minimizes the chances of lifting one of the pads and or traces)

 

[Tridacnid]

Quote:

Originally Posted by MisterX /img/forum/go_quote.gif I would just cut it off, it's a little safer to remove the remaining bits one at a time then it is to try to remove the op-amp by heating all of the pads at the same time (minimizes the chances of lifting one of the pads and or traces)

THIS! I've lifted way too many pads before. Don't try to do it "the easy way."

 

[MisterX]

After trying it and liking it, I think the "easy way" is to use that chip quik kit but convincing people they need a $14 product to remove a dead SMD chip is a bit of a stretch.

 

[Mizu]

I would buy them if I knew where to order... All soldering shops near me offer basic stuff but nothing really useful.. Can't even get that ST6 tip for my solder iron..

Or else, I can't even find solder that doesn't come with flux already.. you should see my board.All I have is a mix of silver and flux which needs more temp to melt, so higher chances to damage the Opamps.

I'll try the chip quick solution, as removing the U5 once damaged the board.

 

[pdupiano]

you can get chipquick from most places, mouser even keeps them in stock. But yeah I agree with Mister X, its pretty tough to justify $14 cost for a one time use unless of course you have other projects or you also have to replace other work. Id suggest the cut technique to save yourself some cash. And yeah don't use silver solder on this stuff... just dont...Well maybe you can get away with the quad-eutectic solder but thats about it because its still a lead alloy. The other silver mixtures just require too much heat to be useful.

 

[Mizu]

Could you guys point me a specific solder that I can buy which is best suited for boards work ? I'm getting lost with all the choices..

 

[m1abrams]

Quote:

Originally Posted by Mizu /img/forum/go_quote.gif Could you guys point me a specific solder that I can buy which is best suited for boards work ? I'm getting lost with all the choices..

Plan jane 60/40 will work just fine. You can find it anywhere including radio shack.

 

[MisterX]

Digi-Key - KE1106-ND (Kester Solder - 24-6040-0027)

 

[Mizu]

thanks for the tips ! I'll try to cut the pads of U4 and install a new one, will get you updated !

 

[Mizu]

Do I need special cutters ? I have one but it's kind of big for the task.