Loss of pads

[MattL]

I had to remove resistors from a Slambox PCB and the pads came up in a couple of places. Does this necessarily mean the circuit won't work right? In asking this (pardon the newbie ignorance) I'm trying to determine whether the circuit may work, say sans a resistor for example, making it harder for me to determine if it's working as designed, as well as if this happens in the future if it's worth bothering to finish a pedal. Thanks to whomever might leave an answer...I'm sure I'm not the 1st person to have this happen! Matt

[jkokura]

No, you're not the only person it's happened to. Pretty much anyone who's built a few circuits and has needed to take a few parts off their PCB has had this problem.

It 'may' mean it won't work right, but usually you can fix it. If the pads are still attached to the traces, you can use your soldering iron and a tooth pick to get them back to where they belong. If the trace has broken and the pad and trace have completely off the box, you can attach the part right to where it should be attached to. If you're not understanding me, take some pictures of your board, make sure they're in focus, and then post them and we'll try to indicate where to connect the parts.

Usually a circuit won't work if you leave a part out. You need to make sure everthing's connected right. Sometimes you can leave a part out, but you still need to jumper the part that's left out, meaning you connect the ends of the parts that are connected to either side of the part you took out.

Jacob

[MattL]

Thanks a lot Jacob, that's reassuring - if I'm reading you right, it should work!

[madbean]

Matt, as Jacob said pads lifting is an unfortunate consequence of brute force desoldering with these kinds of boards. They are definitely not as forgiving as handmade ones.

When this happens all you need to do is run a small bit of wire from the lead of the lifted pad to wherever it is being traced to. For example, if you lift the pad under R3 here


Then you can run a small bit of wire, OR use a new resistor and simply fold the lead over and solder it to the next component that it should be connected to (as if you were working with perf)


Here's a little trick to removing resistors: melt the solder joint on one pad while simultaneously lifting the end of the resistor with a small tool like a tiny screwdriver. Once that end clears the joint, bend it so that the resistor faces straight up. Now, hold onto the free end with small pliers, melt the other joint while gently lifting the resistor out of the pad.

Of course, you still have to clear the solder out of the joints if you want to put another resistor in there! You should be using desoldering braid for that. You have to be very careful and it takes time to get solder out of a plated through hole pad. Sometimes it actually helps to add a little solder back to the pad first before using a desolder braid.

One tool that will help is a $10 desoldering pump from Radio Shack. It can make those kinds of repairs much easier.
http://www.radioshack.com/product/index.jsp?productId=2062745

[MattL]

Thanks a lot, because I finished it today and it doesn't work, but I also had a question about grounding with the switch diagram, because I'm building these without batteries and am a little confused because I'm left without a ground on the input sleeve, and can't find a spot with alligator clips that works. Should I ground that to the sleeve of the output jack? All the other wiring I've followed accurately but the absence of the battery leaves a hole (in my knowledge!). Also, Does SW have an equivalent on boards by other makers? I need to know what to do if I use the tonepad switch wiring...what would go to SW?

[madbean]

If you are using open frame metal jacks, you only need to ground the sleeve of one of them (input or output). The other jack will be grounded via contact with the enclosure (provided the inside of your enclosure is unpainted). If you are using Marshall style jacks, which are plastic enclosed, then you should ground the sleeve of both the input and output since neither is grounded through the enclosure.

Next, SW is whatever lug on your 3PDT you are using to toggle your LED on and off. Using the example from Tonepad below, the current limiting resistor and LED have connections on most of my PCB's, and "SW" gets wired to the lug in the circle. When the 3PDT is in the "up" position, it connects the LED to ground which completes the circuit and lights up the LED.

[attachment deleted by admin]

[MattL]

Thanks so much once again!

[MattL]

I know it's always one more thing, but with the part of the switch that turns the LED on connected is there a resistor on the board that is for the LED or do I have to include one as per the tonepad diagram? Thanks, Matt

[MattL]

Oops, I think I have my answer, sorry!

[madbean]

Correct. If the LED has connections on one of my boards, it also has a CLR (current limiting resistor) on there, too. If no LED is pictured, then you need to hook it up similar to the Tonepad way, or other ones.

[MattL]

Thanks again Madbean!