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Shielding one of those new 'PCB' style control cavities (Gibson SG, late 2008)


gnolivos

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As many of you may know, Gibson has started using PCB (printed circuit boards) for some of the wiring on the new guitars, including the SG standard.

 

1) I am planning on shielding the cavity with nickel paint etc, but to do so I need to remove the PCD and components. Has anyone removed this yet? How exactly is it done? It appears that the PCB itself *may* be stuck to the cavity 'floor' itself, against the bare wood.

 

2) Secondly, this PCB setup represents a potential problem for shielding. If the PCB lays flat against the cavity floor, the PCB 'runs' will be touching the grounded shield paint. Doh! This will short circuit no doubt.

 

Any ideas on how best to approach this?

 

PIC:

wiring.jpg

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There really is no need to shield the cavity on an SG with humbuckers.

 

If you're getting noise from the guitar then you should check that everything is grounded properly.

 

I've owned many SGs over 40+ years and have never felt the need to shield any of them as long as they are properly grounded.

 

The best thing that you can do for your SG is to take out the entire PC board assembly with the mediocre pots and put in an RS Guitarworks upgrade kit.

 

You can get them pre-wired, and buy a switch and jack or use your existing switch and jack.

 

http://www.rsguitarworks.net/rsstore/product_info.php?cPath=47_62&products_id=153

 

Or buy a kit with all of the parts and put it together yourself:

 

http://www.rsguitarworks.net/rsstore/product_info.php?cPath=31_59&products_id=419

 

Or pick and choose the parts:

 

http://www.rsguitarworks.net/rsstore/index.php?cPath=45

 

These upgrades are well worth the money and will make a significant difference in the tones available on your SG.

 

I have them on all of my modern Gibsons, and wire them 1950s style, not modern style.

 

If you do decide to shield it anyway, you can do what Gibson did in the '60s and '70s when they started using cavity shield in some guitars.

 

They stuck pieces of electrical tape under the pot terminals to stop them from grounding out on the metal shields that they used.

 

I say that you should ask yourself- if the guitar didn't come with shielding, why do you think that it needs it?

 

Noise issues should be addressed at the source, not by putting in an unnecessary "fix".

 

Don't be offended, just trying to help you.

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Thanks Lous.

 

Sorry, but I have concluded that the reason I have humming is EMI, and shielding is needed to take care of it. My other SG guitar is an Epi, much lower quality in general, but with fully shielded cavity, and it is dead silent. All my grounds are perfect on the Gibson, but humming persists. It is not a 60hz hum.

 

Anyhow, I have a separate thread on that specific issue...so back on topic, looking for comments on how to remove the PCB without damaging anything...

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Lou, no offense, but the reason I think I need the shielding, is the same reason you think that upgrading the electronics is needed! Gibson cuts corners, oh they certainly do...

 

I say that you should ask yourself- if the guitar didn't come with shielding' date=' why do you think that it needs it?

Don't be offended, just trying to help you. [/quote']

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If you think that it needs to be shielded, by all means do it.

 

I would just unscrew the jack and switch and remove it as a unit.

 

You should be able to do it without damaging anything.

 

You can then shield it, and I would use some sort of rubber or plastic sheet for insulation, cut it to fit in the opening and cut out for the pot shafts.

 

That will hold it and keep it from moving around, or you can use something that is adhesive backed.

 

If you decide to upgrade the pots/caps, disconnect the pickups and the ground (from the bridge/tailpiece) from the board, save the board for future sale.

 

You can then disconnect the pickups from the white connector or try to find the mate for the plug and wire the plug to new pots.

 

Same with the ground.

 

This isn't difficult, you just need to be a bit creative.

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You know, a part of me doesn't mind the PCB connections in the non-Historic guitars, because I like the idea of less soldering-iron-playtime (so does my lungs), but at the same time I have to wonder...

 

1) What's gonna' happen if one pot goes mysteriously bad? It's gonna' be a pain in the butt to remove the old pot from the board for one, or if it's not serviceable is that gonna' mean a new component altogether? Wow.

 

2) Is Gibson going to start selling either the PCB-ready switches and pickups or the connectors so we could add them to said pieces? Because again, I love the idea of swapping out pickups in 5 minutes, but if my stuff's not equipped that's gonna' be a problem.

 

Contrary to most people's beliefs I'm not against ALL "new innovations" and whatnot, and while I prefer my classic-styled guitars to have their classic-styled old-school wiring, I don't mind a simple, solid mounting board with connectors like that as a way to speed along production of the USA stuff and make it more efficiently serviceable (if it indeed IS), so long as the components are going to be available for aftermarket purchase.

 

H-Bomb

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I didn't mind the PCB when I first got the '08 SG classic, but now this one has to either go in for warranty work, or I have to replace the PCB with regular stuff.

The guitar sounds awesome...as long as you play it.

Touch the wood (not metal parts) on top of the guitar anywhere near the knobs.....Static crackles through the amp like a witch laughing from you.

I don't like that PCB at all.

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Wow, you know, I noticed that myself but feared to mention because people would call me crazy.

 

If I rub my bare arm over the top 'horn' of my SG (2008 standard), it produces a crackle sound. Every time. I can't imagine it has ANYTHING to do with the PCB itself though. What's up with that?!

 

Touch the wood (not metal parts) on top of the guitar anywhere near the knobs.....Static crackles through the amp like a witch laughing from you.

I don't like that PCB at all.

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I get static crackling sounds too. If I keep touching the metal it goes away until I generate more static.

Do you live is a cold dry climate?

I read some people put bounce sheets in the control cavity to avoid this.

I also read allot of static could be produced from the pickguard. Try rubbing the pick guard with a bounce sheet as well.

I live in Canada and it is very cold and dry this time of year. Allot of static!

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If I rub my bare arm over the top 'horn' of my SG (2008 standard), it produces a crackle sound. Every time. I can't imagine it has ANYTHING to do with the PCB itself though. What's up with that?

 

Its very common - its due to static electricity, and the micro discharges are being coupled into the pickups. Heard as "rice crispy" like crackles as you rub your hand on the plastic pick guard. - Very common problem.

 

solution ?

Cut a "bounce" static control sheet and place it under the pick guard.

 

more severe cases are best solved by Lining the backside of the plastic pick guard with copper foil and cleverly ground it with a hidden wire under a PU ring ('61-65") or to the back one of the pick ups ('69 type)

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Interesting. My other SG (epi) never does this though, side/side comparisons. The only difference is that the epi has a fully shielded cavity control. nothing done on the pickup cavities from what I could tell.

 

 

 

 

Its very common - its due to static electricity' date=' and the micro discharges are being coupled into the pickups. Heard as "rice crispy" like crackles as you rub your hand on the plastic pick guard. - Very common problem.

 

solution ?

Cut a "bounce" static control sheet and place it under the pick guard.

 

more severe cases are best solved by Lining the backside of the plastic pick guard with copper foil and cleverly ground it with a hidden wire under a PU ring ('61-65") or to the back one of the pick ups ('69 type) [/quote']

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Its true - the Epiphones's have much better shielding which blocks outside interference from RF, static, and limits cell phone message checking interference - compared to Gibsons.

 

The last well shielded Gibson's were from the Norlin era in the 70's - when all electronics were 360 degree encapsulated in earthed metal shield. Norlin did many things to upset a few purests - but they typically did a good job on the electronics.

 

Current Gibson's just skimp or have zero shielding - and I'm rather surprised to discover this on such a high end guitar.

 

Gibson's electronics R&D guys should go to Guitar Center on a lunch break with a screw driver and an ohm meter and inspect the competition.

 

Just about any guitar built today must meet "CE"approval - Gibson is obviously bypassing this important step - because I have yet to see one that would pass a CE inspection.

 

 

Compare -

 

1967 SG shielded control cavity - they even lined the back of the plastic cover with metal foil shielding!

potguts.jpg

 

 

2008 SG unshielded control cavity - = no proper shielding means stray EMI magnetic field noises are induced into the the Hi-Z audio signal path. The PC Board is there for one thing - assembly speed - the quick disconnect PU and Earth connectors mean zero soldering on the guitar assembly line, reducing a 5 minute task to 90 seconds.

 

wiring.jpg

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Its true - the EPI's have much better shielding which blocks outside interference from RF, static, and limits cell phone message checking interference - compared to Gibsons.

 

The last well shielded Gibson's were from the Norlin era - when al electronics were 360 degree encapsulated behind earthed metal shield.

 

Latest ones just skimp - rather surprised.

 

Their electronics R&D guys should go to guitar center on a lunch break with a screw driver and inspect the competition.

 

Just about any guitar built today must meet "CE"approval - Gibson is obviously bypassing this important step - because I have yet to see one that would pass a complete CE inspection.

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Sad. I actually had the control cavity of a '61 re-issue opened at GC for me, and it was not shielded either. Gotta say, Gibson really sucks for skimping on the shielding. Done in factory, it is MUCH less hassle than having the customer rip everything aprt for shielding. And the fact that the cheap-o Chinese/Korean Epis are *perfectly* shielded makes me want to cry.

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I would

 

* Use a video camera and digital camera to record all steps of disassembly.

 

* Line the control cavity with copper foil -

 

A shielding kit is available from Stewart McDonald $13.75

http://www.stewmac.com/shop/Electronics,_pickups/Supplies:_Shielding/Self-adhesive_Shielding_Kit.html

 

* Dont forget to apply copper foil to the back of the plastic cover.

 

* line the area directly under the factory PCB with an insulator - in the electronics field we call this material "fish paper" - I admit I have occasionally improvised this by using a manilla folder material from Staples or Office Depot.

http://www.jjorly.com/fish_paper_die_cut.htm

 

* Reinstall the factory electronics - taking care not to short out the PU switch or Output Jack to the Copper foil

 

Refer to your pictures & video for proper component orientation.

 

Solder a wire from the copper foil to the earth connection (green ZIF connector on PCB)

 

 

Petition Gibson to read this thread and get them to do the job right the 1st time.

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  • 3 months later...

Can anyone show me via pics what the diff is between what a PCB looks like and the original style electronics. I'm going back and forth with Roger at Gibson and he says I don't have it n my newish SG but I say yes. He saw pics of mine and I am looking above and it looks identical to the above pic GNOLIVOS feautured above in this thread. Thanks. I am a newby! (Mine is pic'ed below)

 

3608068340_2c642cd4d5.jpg

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By mounting a PCB, Gibson is saving assembly costs. It's more expensive to get qualified persons to solder in the wiring then have a normal assembly operator can just drop in a PCB and snap together the connectors. All of which is perfectly legitimate technically speaking. Over all, the whole wiring and PCB look to be very good for consumer quality.

 

The PCB should have isolation to protects it from the wood. No electronics engineer would design something that would short out to a potential ground or conductor. I don't know the value, but I'm pretty sure that wood is conductive in some amount even if in Mohms.

 

In the pictures here you see that the PCB directly mounted on the wood, but it's made of some polimer material and not normal fiber glass, so it looks like Gibson did their homework well. To remove it, you should only have to remove all of the holding nuts and unsnap the pup's connectors, CAREFULLY. I think that I'd first try to just shield the access cover and sides to see if thats enough, you'd have to however install a ground wire to this shielding to keep from make more noise.

 

Watch out though, if you pull the PCB out, you may void the warranty.

 

Usually a cavity would be shielded against radio frequencies. If all of the pots, pups and all are grounded together, then they'll act like an antenna if not, so it makes sense to shield it the whole thing. Gibson is not a stupid company and I don't believe that the'll cut corners without evaluating it carefully first. My SG Classic hum like hell, but it comes from the pups that are just big antennas. I roll off the volume when not playing.

 

Static electricty generated by rubbing your hand on the finish or pick guard can create high voltages, maybe a few hundered volts, so it's no wonder that the pups may pick that up, or an unprotectecd cavity will detect it by means of capacitance.

 

If you do decide to remove the PCB, then just for safety's sake, make sure that the PCB and shielding don't short to each other directly, but put some kind of isolation between the two. Also, you'll have to connect all shielding to the guitar's grounding. Pot bodies solder joints for example.

 

Also if you get noise by touching the outside of the guitar, it's because you're also an antenna and transmitting into the circuitry. If you want to shield the pickgurard without grounding it to the ground wiring, it will also become capacitive, possibly inducing more noise. I wouldn't ground or shield anything that I don't have to.

 

Hopefully this helps, I've work in various forms of electonics for my entire working career. I'm not a genius or a sound engineer, but this so far is just simple electronics. If I forgot anything, pls comment.

 

I'll try to get a minute to open the access cover on my 2008 SG Classic and see whats inside.

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Just to close my comments.

 

I checked out my SG Classic with following

 

- no noise problem even when the guitar/amp are turned up to high volumes. OK, I have to hold the strings and stay away from the amp because the P'90's will feed back but I don't have any problem by touching the body or pick guard.

 

- I opened the electronics cavity and I have the exact same PCB assembly. I have to say that I was suprised to see such a high quality of consumer electronics. Usually consumer grade is the lowest. Then comes industrial and top quality is military grade. The pick-up shielding is fantastic, no cheap foil wounded cables, good quality wire braided shielding. The connectors are good also. Pots all say Gibson, I imagine that they are resistive disc type, which is fine in my opinion.

 

I believe if someone has a noise problem, it's possibly due to something gone wrong in assembly. Maybe someone put star washers under the PCB, maybe where the pots are mounted. If you stil have a valid warranty, bring it to the shop. If you feel capable of disassembling the PCB assembly, then do it (carefully), you don't want to put cracks in the PCB.

 

I don't agree that there is a design error unless there is a revision that had defects of some sort. In that case you'd see some kind of electrical short to ground, ground being the guitar body. There's nothing keeping you from measuring the PCB ground to guitar body with and ohm meter. For a reference, you'd want to measure also the body to body resistance too.

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