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Thread: Champ 600 EQ mod balls-up!

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    Junior Member Tumshie's Avatar
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    Champ 600 EQ mod balls-up!

    Ok, I'm sure I'm going to get stick for this but here goes.

    I decided to do the famous EQ mod on my Champ 600. Pulled the chassis, soldered my wires and pots as per my mod diagram then removed the four relevant resistors and soldered in my pot. Switched it back on and ......nada, no EQ. Given that I've never worked on a PCB before, I think I made a mistake going in 'on top' instead of underneath. Realising this, I pulled all the jumpers and flipped the PCB. The holes were burn out.

    I managed to put three wires back in but they don't seem to be 'taking' to the PCB cleanly though I have continuity between them and certain other points on the PCB that I'd expect to find it. I have some conductive paint on the way but is there anything else I need to get to surround those burned out holes to accept the solder?
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    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by Tumshie View Post
    I have some conductive paint on the way but is there anything else I need to get to surround those burned out holes to accept the solder?
    Never had much success with conductive paint. It looks like at least one of those solder pads has broken off, not point in trying to replace, just get the remnants out of the way. Scrape (carefully!) green varnish off the traces you need to reach until you see shiny copper, then you can bring your component leads thru & solder them to those traces.

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    Woodgrinder/Pickupwinder copperheadroads's Avatar
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    I don't think conductive paint is a fix for that & take Leo's advise .clean off the trace & jumper to the problem component .

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    Junior Member Tumshie's Avatar
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    Quote Originally Posted by Leo_Gnardo View Post
    Never had much success with conductive paint. It looks like at least one of those solder pads has broken off, not point in trying to replace, just get the remnants out of the way. Scrape (carefully!) green varnish off the traces you need to reach until you see shiny copper, then you can bring your component leads thru & solder them to those traces.
    Thanks for the assistance. So, it's still salvageable, then?

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    Old Timer olddawg's Avatar
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    Quote Originally Posted by Tumshie View Post
    Thanks for the assistance. So, it's still salvageable, then?
    The best tool for cleaning traces is a fiberglass pen imho. Use flux and the appropriate sized copper lead wire. The small Teflon insulated type works best for me. If a "feed through" has been damaged run a wire through it. It may require a tiny drill bit. Use a hand chick. Measure continuity where the components meet traces.

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    Junior Member Tumshie's Avatar
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    Quote Originally Posted by copperheadroads View Post
    I don't think conductive paint is a fix for that & take Leo's advise .clean off the trace & jumper to the problem component .
    Ok. Jumper with what? Solder or insulated wire?

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    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by Tumshie View Post
    Ok. Jumper with what? Solder or insulated wire?
    Best would be to use the leads on the components you installed. Push the lead thru the hole, bend it towards the circuit board land you cleared varnish from, solder away.

    Cut the leads too short? To cover the fraction of an inch from the holes to the places you need to solder to, no insulation necessary, leftover leads cut from components or any skinny copper wire will do.

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    Junior Member Tumshie's Avatar
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    Quote Originally Posted by Leo_Gnardo View Post
    Best would be to use the leads on the components you installed. Push the lead thru the hole, bend it towards the circuit board land you cleared varnish from, solder away.

    Cut the leads too short? To cover the fraction of an inch from the holes to the places you need to solder to, no insulation necessary, leftover leads cut from components or any skinny copper wire will do.
    Ah, ok. That makes perfect sense.

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    Old Timer olddawg's Avatar
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    Quote Originally Posted by Tumshie View Post
    Ok. Jumper with what? Solder or insulated wire?
    Honestly.... it's going to depend on the damage. It's great if you can use a bit of component lead, but if you have inches of trace burned or lifted you are going to need to use lead wire. Many times if you have large mounted radial caps and double sided boards you have to jumper around the board. Every situation is different. The important thing is you do it cleanly and reliably. Use flux. Clean up afterward. Cook the unit for a while when it's fixed. Especially if it's a combo, a dab of 5 minute epoxy at stress points can keep you from having to repeat the repair.

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    Junior Member Tumshie's Avatar
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    Quote Originally Posted by olddawg View Post
    Honestly.... it's going to depend on the damage. It's great if you can use a bit of component lead, but if you have inches of trace burned or lifted you are going to need to use lead wire. Many times if you have large mounted radial caps and double sided boards you have to jumper around the board. Every situation is different. The important thing is you do it cleanly and reliably. Use flux. Clean up afterward. Cook the unit for a while when it's fixed. Especially if it's a combo, a dab of 5 minute epoxy at stress points can keep you from having to repeat the repair.
    Have a quick look at the photo; it doesn't look that bad, does it? I was worried about the burnt-out areas.

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    Last time I had a damaged PCB, I took pictures of both sides of the board. Then I sanded off the remaining traces, drilled out the lifted pads, put in turrets, and used wire to serve as traces. Depends on how close your traces are, etc, though. The nice pat is that the PCB lugs on the switch I was replacing fit into the turrets perfectly. Granted this was a tiny board, but it worked.

    Justin

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    Old Timer olddawg's Avatar
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    Quote Originally Posted by Tumshie View Post
    Have a quick look at the photo; it doesn't look that bad, does it? I was worried about the burnt-out areas.
    Sorry... for some reason the picture didn't come up initially. That's really minor. If there are connected traces on the other side you have to be careful of that. Looks like some bits of component leads, as was stated previously (off of a resistor or something), should do nicely. Just solder them across the connection points.... effectively jumperjng the trace. But like I said. Look at the other side of the board too. You have to think in 3 dimensions.

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    Junior Member Tumshie's Avatar
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    Quote Originally Posted by olddawg View Post
    Sorry... for some reason the picture didn't come up initially. That's really minor. If there are connected traces on the other side you have to be careful of that. Looks like some bits of component leads, as was stated previously (off of a resistor or something), should do nicely. Just solder them across the connection points.... effectively jumperjng the trace. But like I said. Look at the other side of the board too. You have to think in 3 dimensions.
    Those two arrowed points are the newly soldered ones but I'\m gonna have to redo them.

    Thanks for all your assistance, guys.

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