Boneyard high gain troubles

[jolly1423]

So my boneyard sounds great! Except one thing. There's no difference between the normal channel and the high gain channel. And the high gain knob affects the gain level while in crunch mode. The two gain knobs are quite interactive while I don't believe they should be. In the crunch mode, if I turn the high gain knob all the way down it'll cut the signal completely. If you read across the top of the board, left to right, the wholes go- crunch 3-2-1 and then high gain switch 3-2-1. When the switch is off should I have continuity between switch lugs 2 and 1? Because I do, however I get the same for the boost switch and that functions normally. Any thoughts on what else to check?

[oldhousescott]

Can you post some hi-res pics of the solder side of the board? It sounds like perhaps the hi-gain pot is shorting to ground at lug 1 somehow. It could be a solder bridge since pad 1 for the hi-gain pot is near a ground trace. Voltage readings at all pins on both ICs would be good to have as well.

[jolly1423]

I can't pst a pick right now, but I will try tomorrow. I tested all along both gain pots and the gain switch and nothing showed continuity to ground or anywhere I could tell there shouldn't be. I do have voltages though.

For the lf347, the left side (I assume that's 1-7 going down?) 9.39v going in, 1=-.55 2=0 3=0 4=9.39 5,6,7=0
The right side 8=.01 9+10=0 11=-9.06 12,13+14=0

The 1044, 1=9.39 2=4.65 3=0 4=-4.59 5=9.39 6=4.01 7=4.61 8=-9.06

Like I said, I'll get a pic up tomorrow but until then, any thoughts? That's seems like a lot of 0's to me but there's a lot I don't understand about how these work...

[oldhousescott]

Voltages look good. Since the unit is getting plus and minus 9vdc from the 1044, Vref is at ground, so you should be getting zero volts at all the inputs and outputs of the amps.

Maybe pics will show us something.

[jolly1423]

[BraindeadAudio]

A few of those joints look cold, reflow the board and add a little more solder on that one pin of the IC thats missing some. Did you socket the IC? Ive made it a point to socket every IC I can, due to blowing up an MN3007 by overheating it when I first started making pedals. the 50 cents you spend now saves a ton of headaches later.

[jolly1423]

Ok, I'll try that. And yes, I did socket it. Just makes good sense to take that risk and potential trouble shooting time out of the equation. 

[mgwhit]

I don't think this is causing your problem, but the joint at G1 needs to be reflowed.  Notice how it's a blob that clings to the wire and doesn't appear to spread down on the copper.  Even if it's making contact now, it could be really susceptible to mechanical stress and become intermittent later.

[jolly1423]

So I re-flowed that whole side of the board and the lugs on the high gain switch and it's working much better! Way more separation between the two channels. Although I still get a little bit of interaction between the two pots it's way less noticeable, only cuts gain when the high gain knob is all the way down, otherwise they're mostly independent. Sounds freakin' awesome! Thanks for the help guys