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Thread: PCB Trace Repairs

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    PCB Trace Repairs

    I've got an amp that at least 1 person has worked on & there are a bunch of traces & pads lifted. Quite a few of them could just be glued back down, but some need to be replaced or jumpered. I'm wanting to make these repairs as clean looking as possible, so I don't want to just run a bunch of jumper wires around if I don't have to.

    Looking at PCB repair kits online, they seem to cost between $200 & $300. I could literally redraw the board using something like PCB123 (it's a simple 1 layer board) & have a new board made for much less than that!

    I have 2 questions:

    1. What type of epoxy can you use that will handle the heat of soldering?

    2. Is there an inexpensive trace kit that anyone has found to replace 5-10 traces?

    Thanks.

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    ST in Phoenix

  2. #2
    Noodle of Reality Steve Conner's Avatar
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    I never even knew such a thing as a "PCB Trace Repair kit" existed. I've repaired and modified hundreds of PCB-based things, and I just use jumper wires.

    Offcuts of component legs are great, because they're short, stiff pieces of solid copper wire. You can do a neat job with them, and there are always lots of them lying around the workbench, though not so much in this age of surface-mount components.

    For longer jumper wires, you can use hookup wire and stick it to the board with hot glue. Pretty is what works, and so on.

    I don't know of any epoxy that can stand the heat of a soldering iron. It must exist, though, because epoxy is what sticks the copper to the board in the first place.

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    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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    "Circuit Works" pens are available from a few places down here.
    In the US probably RS components,Tandy or Radio Shack?
    These are a pen dispensing a polymer with silver powder.
    I have repaired hair thin tracks with these in the past, spreading the liquid with a scalpel blade, and if you can get low temperature solder it is possible to solder to the cured polymer.

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    Lifetime Member Enzo's Avatar
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    I'm with Steve. Whenever I install a new resistor or cap, I cut off the excess lead, and I keep the pieces in a little film can next to my iron base. Little inch long pieces of solid wire. I then can form them to the shape of any trace, or bridge a gap with them, etc.

    Whenever I have a crack across a trace, I never just bridge it with solder, I always runa piece of bare wire across the gap and solder it down onto the trace on either side of the break.

    Jacks that have torn their pads free? bend a little loop in one end of the wire to make a new "pad." then sweat the rest of the wire to the trace leading up to it.

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    Normally, I would do the wire repairs, but this board has wires soldered to the edge connectors. I'm not sure what they were thinking when they designed this.

    One example below just needs to be glued back down so that it is strong enough to solder the connect wire to. Otherwise, I'll probably has to extend the wire to tack to another point, making it even uglier. The other pic shows where I have a trace that curves around things & another one that is quite long, eliminating the short solid wire option & requiring me to glue the replacement wire down. The pads for several pots (not pictured) have broken free, too. I'll have wires all over this board by the time I'm done if I do the repairs that way.

    I'm hoping for a clean look when I'm done. The repair kits are slick, but way more $$ than makes sense for this job.
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    <Rant> I hate it when people who don't know how to solder hack up amps & pedals. Why do musicians think they should learn to solder on their vintage gear? </Rant>

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    Old Timer J M Fahey's Avatar
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    Hi Phostenix. Fully agree with your <rant>.
    I see the main problem lies in the edge connectors pads.
    I'd suggest briefly melting the solder in each of them and quickly sweeping the solder with an outside movement , using a paper napkin, so as to practically remove the thick sloppy solder, leaving it just "tinned" with a very thin layer, so it can be plugged in the connectors, at least for "mechanical", mounting reasons.
    Then you can bypass the connectors with short strips of wire, from the connector wire terminals to the corresponding component or pad in the PCB.
    You'll have an electrically functional board that has lost it "Plug in ness", (big deal), and a (presumably) happy customer.
    Of course, all component to component lost tracks or pads on the PCB itself should be repaired as suggested above.
    And in a desperate case, this particular board looks like it can be duplicated with not too much effort.
    I usually photocopy it to have a flat, 1:1 image, reinforce the track and pad images with some black marker, "filling in" lost parts, and then hand trace it, with a technical drawing pen and india ink on tracing paper.
    That "clean" image can be used to make a new board using any of the usual methods, from laser transfering to photopositive board.
    You can have a new board in 2 to 4 hours, you'll know whether it's worth the effort or not.

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    I would like to learn to layout PCBs & this board just may give me the motivation to learn the software. I have some other little things I'd like to have boards made for....

    These edge connectors are not "real" edge connectors. The wires are soldered to them. Horrible idea.

    Here's what a factory board looks like:
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    Senior Member guitician's Avatar
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    In your case, I would just run the wire over to the component lead and loop the end around it. Your not doing a restoration on it, are you?

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    Quote Originally Posted by Enzo View Post
    I'm with Steve. Whenever I install a new resistor or cap, I cut off the excess lead, and I keep the pieces in a little film can next to my iron base. Little inch long pieces of solid wire. I then can form them to the shape of any trace, or bridge a gap with them, etc.

    Whenever I have a crack across a trace, I never just bridge it with solder, I always runa piece of bare wire across the gap and solder it down onto the trace on either side of the break.

    Jacks that have torn their pads free? bend a little loop in one end of the wire to make a new "pad." then sweat the rest of the wire to the trace leading up to it.
    Preach it, brother. I'm with you on that.

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    Lifetime Member Enzo's Avatar
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    I don't think those edge connectors were ever intended to, well, edge connect. I think the board designer intended them as solder pads, and used the readily available edge connector trace art patterns, why not.

    I am not above drilling holes in the board to bring wire ends through. This provides some strain relief. ANd for that matter, if an edge pad has ripped away, I am not above soldering a wire to a component lead at the trace's destination. Pretty-schmetty, it is about getting the amp back into service.

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    Quote Originally Posted by guitician View Post
    Your not doing a restoration on it, are you?
    Yes, that's the goal. Resale value & pretty-schmetty.

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    Senior Member guitician's Avatar
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    Ok, then you could get a hold of some copper foil and a two part epoxy. Trace the lines to the foil and tape it down with some double sided tape and exacto knife your new traces. Then very carefully apply a very thin film of the epoxy to the underside of the new trace and very carefully position it to the PCB. Be sure to spend days doing this to maximize the quality of the work.

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    Any idea which epoxy to use?

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    Senior Member guitician's Avatar
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    Quote Originally Posted by Phostenix View Post
    Any idea which epoxy to use?
    I think cured epoxies can all handle the heat of soldering in short durations. That is why they lifted in the first place. Too long of a heating and the bond breaks.

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  16. #16
    Noodle of Reality Steve Conner's Avatar
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    I agree with Enzo! Where a pad terminating a wire on the board has ripped away, you should drill two small holes side by side with a Dremel, and pass the wire through them for strain relief. Then use a jumper wire to replace the busted pad.

    Or if you're really diligent, replace the wire with a longer one that can bypass the busted trace and go all the way to the nearest component leg.

    What potential buyer is going to open the amp up and look at the PCBs?! If they ask, just say no. Spend the time and effort pimping up the outside of the thing where it'll show, instead. It's only an Acoustic 370 anyway.

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    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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    Quote Originally Posted by Steve Conner View Post
    It's only an Acoustic 370 anyway.


    Says the anti-SS, anti-PCB crowd.

    There seems to be a very loyal following for these amps. And, just like most vintage gear lovers, they're very concerned about originality (right or wrong).

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    Noodle of Reality Steve Conner's Avatar
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    Sure, they have a loyal following, but the loyal followers could all be broke. What did the last Acoustic 370 sell for on Ebay?

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    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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    Old Timer J M Fahey's Avatar
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    Old Acoustic amps from the early 80's had "plug in board" edge connector pads or fingers along the edges, but always were soldered. Maybe for neatness.
    I *draw* my boards with connectors, but never use them, just solder the wires straight into the holes and after assembly run a contact cement line on both sides, to protect wires from vibration o flexing damage.
    Speaking of a possible new, cloned board, you don't need to know any software at all, if you hand trace it as I suggested earlier.
    Of course, that works on relatively simple boards as this one, which was not drawn with any PC at all, but with good old hand laid black crepe tape and donuts.

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    Quote Originally Posted by Steve Conner View Post
    What did the last Acoustic 370 sell for on Ebay?
    $400

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    Noodle of Reality Steve Conner's Avatar
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    OK, so if they sell for about $400, how much effort do you think is worth putting into restoring one? How much is your time worth, and how much profit do you think you'll make on the sale? In that context, is it a priority to have a perfectly repaired PCB that you couldn't tell apart from a new one?

    These are good amps, but in a workhorse way, not some boutique plexi pooch that might change hands for ten times that amount.

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    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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    Lifetime Member Enzo's Avatar
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    SO it compares in value to a new Crate 2x12 something.

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    Conductive paint could be worth testing.

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    The conductive pen trails always seem to look messy to me.

    I wouldn't mind making another board by hand, but I figure if I'm going to take the time to make a board, I might as well learn how to use board layout software so I can have that skill.

    I approach this stuff as a hobbyist, not as a professional repair shop. It's puzzle solving for me, I guess. So, part of the fun is learning new things, not just using the most cost-effective solution. Ideally, I'd like the repair job to look as good as the original. If someone DOES open it up, I don't want them to say, "what hack did all this?". Even if the repairs are solid, if they don't look good, people will see them as sub standard. We've all experienced that (or done it ourselves).

    Circuit Specialists here in the Phoenix area told me a couple of weeks ago (on the phone) that they didn't have any repair kits, but their website lists this:
    CIRCUIT-FIX SYSTEM Complete

    I'll call them again next week & see if I can get a different person....

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    Senior Member bnwitt's Avatar
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    Here is the page for all of their pcb repair stuff. I use their pens, foil stick ons, epoxy etc:

    Printed Circuit Board Accessory Items

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    Warning! Some Electronics devices contain lethal voltages that can kill you. If you do not feel qualified to work with dangerous voltages, refer your repairs to a qualified technician. By giving you online advice, I am assuming no liability for any injury or damages you might incur through your own actions.

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