Carvin Icon with 505S preamp rewire, re-shield & switch mod.

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Carvin Icon with 505S preamp rewire, re-shield & switch mod.

Postby Keith Medlock » 02 Dec 2013, 19:02

Hello all. I got annoyed with my Carvin Icon's preamp switch being the instrument cable/stereo jack. I don't feel like removing the instrument cable every time I'm done playing to avoid battery drain. Therefore, I'm going to add a rotary switch to control the preamp on/off function while still leaving the bass' factory look in tact.

At the same time, I will take the opportunity to completely rewire and re-shield with copper conductive coating, silver epoxy and single conductor shielded 18 awg aircraft wire. This will reduce the circuits overall resistance/current draw and increase protection from RF/EMI. However, it will also lower the capacitance and affect tone in theory although I believe the change will be imperceptible.

I'm sick as shit with an awesome sinus/respiratory/ear infection and bored so I thought It would be nice to take some extra time and post the process for anyone else interested in doing this to their instrument. For the sake of this thread, I'll start with my Carvin Icon disassembled/gutted with the new rotary switch hole drilled.

If you want to know what I started with, look at stock Icons on the Carvin site. If you don't know how to disassemble your bass or drill a hole into the instrument cavity to get to where I'm beginning this thread, you may not want to attempt the rest of it either.
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Re: Carvin Icon with 505S preamp rewire, re-shield & switch

Postby DrNomis » 02 Dec 2013, 19:26

Personally, I think the wire capacitance is going to be too small to make any noticeable change in the tone, the capacitance is probably going to be something like a few pF...... :thumbsup
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Re: Carvin Icon with 505S preamp rewire, re-shield & switch

Postby Keith Medlock » 02 Dec 2013, 20:28

DrNomis wrote:Personally, I think the wire capacitance is going to be too small to make any noticeable change in the tone, the capacitance is probably going to be something like a few pF...... :thumbsup


I agree 100%. I'll be able to measure it but I won't be able to hear it.

Distance between holes is approximately 41.5mm and hole is diameter approximately 8mm so the new hole was placed to be uniform with the factory pattern.

Aluminum foil tape removed from control cavity cover.
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Re: Carvin Icon with 505S preamp rewire, re-shield & switch

Postby DrNomis » 02 Dec 2013, 22:44

Looks nice so far, I'm in the process of building a headless guitar from a kit I bought online, the only problem is that the bridge wasn't of good quality (it's one of those Overlord Of Music types, and looked a bit like Steinberger's R-Trem), consequently the main string-tensioning knob stripped it's threads so I need to buy a new replacement for it, also the weather's been a bit damp lately so I've had to put the thing on the shelf for the time being.... :thumbsup
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Re: Carvin Icon with 505S preamp rewire, re-shield & switch

Postby Keith Medlock » 02 Dec 2013, 23:47

Thanks DrNomis. Good luck with your build. Sometimes the hardest part of a project is patience.

Initial solder tac of the three long prongs on the stereo jack. They'll all be ground now and the short prong will be for signal. Once the ground wire is in place I'll pretty it up.

Copper conductive paint won't bond to the shiny plastic cover so it needed some prep. First it was wet sanded to 400 grit and cleaned with wax & grease remover to get rid of any mold release agents. Then it was masked on the outside, sprayed with adhesion promoter and top coated with sandable primer. In 24hrs I'll wet sand the primer to 400 grit and it'll be ready for a thick conductive coating, bonding strap and perhaps even a brass hinge if I'm feeling feisty!
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Re: Carvin Icon with 505S preamp rewire, re-shield & switch

Postby Keith Medlock » 03 Dec 2013, 06:26

The original wiring had the series wire between the batteries routed through the control cavity. The new setup will make both battery holders one piece with the series wire directly run, reducing the length of wire to 2cm.

To keep the factory look I fabricated a thin black plastic bonding strap to connect the holders from underneath. All of the mating surfaces were buffed to 3000 grit to ensure a good cyanoacrylate weld between the pieces.

The new strap was tac'd down with a tiny bit of CA just to hold it in place temporarily. The top of the strap was coated with CA and the battery holders were put in place. I used the factory screws along with locking pliers to hold everything together nice & tight. In 24 hours I'll carefully pry up the holders, breaking the CA tacs I used to temporarily hold the strap in place. This will damage the UV cured polyester finish, but that has to be removed to allow for the thickness of the new bonding strap anyway and all will be hidden.
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Re: Carvin Icon with 505S preamp rewire, re-shield & switch

Postby Keith Medlock » 03 Dec 2013, 20:04

Filled two existing holes with poplar dowel and drilled the new wire routing hole. In 24 hours I'll cut the excess dowel away.
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Re: Carvin Icon with 505S preamp rewire, re-shield & switch

Postby Keith Medlock » 03 Dec 2013, 20:48

Polishing the battery holders. Notice the ceiling fan reflection.
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Re: Carvin Icon with 505S preamp rewire, re-shield & switch

Postby DrNomis » 04 Dec 2013, 10:20

I was just wondering, have you ever thought of using copper foil to do the shielding?..... :hmmm:
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Re: Carvin Icon with 505S preamp rewire, re-shield & switch

Postby Keith Medlock » 04 Dec 2013, 16:21

DrNomis wrote:I was just wondering, have you ever thought of using copper foil to do the shielding?..... :hmmm:


Actually, this bass came with the control cavity lined in copper foil. I removed it to fill the holes, etc. Conductive coatings are more expensive, but much easier to work with. I can cover everything including the inside of the wire passages in less time than it would take to refoil just the control cavity.
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Re: Carvin Icon with 505S preamp rewire, re-shield & switch

Postby Keith Medlock » 04 Dec 2013, 23:06

Ground most of the poly out, routed a channel for the new wire, used wood filler on the deep imperfections, sanded, masked and primed.
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Re: Carvin Icon with 505S preamp rewire, re-shield & switch

Postby Keith Medlock » 05 Dec 2013, 00:56

Battery holders are done.
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Re: Carvin Icon with 505S preamp rewire, re-shield & switch

Postby Keith Medlock » 05 Dec 2013, 04:59

Soldered the 18awg solid copper conductor to the bridge and got the new switch ready. 6 pole 2 position because the size/price was right. Coated the action with lithium grease.
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Re: Carvin Icon with 505S preamp rewire, re-shield & switch

Postby Keith Medlock » 06 Dec 2013, 06:58

Control cavity cover is polished. I removed the series protection diode and replaced it with a fuse and parallel diode to eliminate voltage drop. Diode soldered to fuse block and entire assembly soldered to the new switch. The factory wiring used neg as switch, but the new setup will use pos, so I scrapes new contact points and soldered one pot on each board to ground.
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