[sdiy] PCB layout mistake = Aaron curls up in a ball in the corner and cries

[Tom Farrand]

Aaron,

Aaron = human;    //Will make mistakes ... it's OK

To repair:
1) Relax ... anxiety only creates more frustration
2) I use X-Acto knife with sharp #16 blade to cut foils - is more
controllable than moto-tool but slower
3) Use wire wrap wire to implement fixes
4) After repairs, wash board in >=91% isopropyl alc. use old
toothbrush to scrub ... and dry thoroughly

The PCB is what is faulty, so I avoid hacking on components (opamps)
themselves, though that might be okay.

Just my $0.02

Tom Farrand


On Sat, Jun 20, 2009 at 11:12 AM, Aaron Lanterman
<lanterma at ece.gatech.edu> wrote:
>
> Feeling overly confident from the success of my Music Easel LPG layout (youtube video to come when I get around to it), I was really excited when five new boards (preamp & env det, pulser, envelope generator, timbre circuit, and balanced modulator) came from PCBCART last week, and I happily built, built, and built. I need to order a few strange resistor values and various pots, but I'm close to being able to start testing everything.
>
> Then, while viewing the schematic of the timber generator, I realized to my horror that I had the +/- on four op amps switched. The feedback was going the wrong direction. How could I have not seen that before in all the time I've spent staring at the schematic? Hmm, I'll need 8 jumper wires to fix that. Bad, but still doable.
>
> Then I reviewed the others. The pulser, envelope generator, and preamp & envelope detector have op amp inputs OK. But on the balanced mod - oh hell, I screwed up the inputs of 11 of the 12 op amps. Aaack, that would require 22 jumper wires! *hits head repeatedly into wall*
>
> What makes it worse is I have a vague recollection of actually switching the op amps from the correct way to the wrong way at some point in a severe brain fart moment.
>
> AAAAAAAAAAAAAAAAARG!
>
> That's a couple hundred down the drain.
>
> I figured it out before I started testing, but I still have most of the parts in. My plan is to solder in the vactrols with only a few leads in, so I can clip them back out and reuse them (I can't imaging committing 7 expensive vactrols to a board that requires 22 jumper wires, which I can't imaging are very stable).
>
> But I do want to try to test everything, so that when I fix the op amps I can fix other mistakes I find to.
>
> So what's the best approach to actually getting a prototype running?
>
> 1) I was thinking of dremelling the traces, but then I thought a quicker solution would be to just clip the input leads on the ICs where the ICs meet the board.
>
> 2) If I take approach 1, is there a "best practices" for soldering jumper wires on top of ICs? I imaging it will be hard to make a stable connection
>
> 3) Instead of 1 and 2, maybe I should unsolder the op amps (I generally solder chips straight into the board without sockets, unless it's a particularly expensive chip to replace, or failure prone like CMOS), put in sockets, and build some "pin switchers?"
>
> - Aaron
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