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1992 Gibson Les Paul Custom - Authentic? What's it worth?


silver_mica

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Looks authentic to me. The Norlin-era Gibson logo says she's a 1970's reissue, albeit the neck-headstock transition has no volute. I'm not sure if or when they remade them on RIs.

 

The pickups obviously are mounted at inverted positions. Their bottoms clearly show that erroneously the neck pickup has "T" and the bridge pickup "R" spacing.

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The pickups obviously are mounted at inverted positions. Their bottoms clearly show that erroneously the neck pickup has "T" and the bridge pickup "R" spacing.

 

Are you saying the pickups have been switched? Bridge pickup placed at the neck location and vice versa.

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Are you saying the pickups have been switched? Bridge pickup placed at the neck location and vice versa.

This is what seems likely to me. One can't exclude for sure it could have happened at the factory, but I think it is very improbable.

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Still curious to know how to identify the pickups - but I don't see any sort of part number in the photo showing the bottom side of the pickups.

 

They do look like the 490R/498T from the period, but there are indeed no specific identifying marks on these to determine the exact models and the same "Gibson USA" stamped base plate was used on other models. It's safe to assume they are this combo if it's suspected that they are the original pickups.

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I'm not 100% certain this was a valid measurement, but both pickups - as measured through a guitar cable - with all potentiometers at the 10 position - measure in the ballpark of 8.8k ohms. Also, I believe I might have a better idea of what @capmaster is talking about. I compared the distance of the pole pieces of each pickup. The neck pickup on this guitar has a wider pole piece spacing compared to the bridge pickup. So, if I understand correctly, the wider spacing is normally for the bridge position and therefore this supports the idea that the pickups have been switched. That is, the neck pickup is in the bridge position and the bridge pickup is in the neck position. Good catch @capmaster !

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I'm not 100% certain this was a valid measurement, but both pickups - as measured through a guitar cable - with all potentiometers at the 10 position - measure in the ballpark of 8.8k ohms. Also, I believe I might have a better idea of what @capmaster is talking about. I compared the distance of the pole pieces of each pickup. The neck pickup on this guitar has a wider pole piece spacing compared to the bridge pickup. So, if I understand correctly, the wider spacing is normally for the bridge position and therefore this supports the idea that the pickups have been switched. That is, the neck pickup is in the bridge position and the bridge pickup is in the neck position. Good catch @capmaster !

The DC resistance readings along with the pole piece spacings would match a set of 490R and 490T.

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The DC resistance readings along with the pole piece spacings would match a set of 490R and 490T.

 

Perhaps this guitar originally came with a 498T - and someone at some point changed that pickup to a 490T. I wonder what the story is behind the pickups having their positions swapped. Accident or purposeful?

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Perhaps this guitar originally came with a 498T - and someone at some point changed that pickup to a 490T. I wonder what the story is behind the pickups having their positions swapped. Accident or purposeful?

Could have been on purpose, the 490 models are very similar to '57 Classics.

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Perhaps this guitar originally came with a 498T - and someone at some point changed that pickup to a 490T. I wonder what the story is behind the pickups having their positions swapped. Accident or purposeful?

I think going from a 498T to a 490T is a sensible step if one is seeking for a more uniform pickup response combined with a 490R. The 490T will have more treble, less level and less midrange edge compared to the 498T. The latter has higher inductance due to more winding turns possible through using lighter wire, and an due to an AlNiCo 5 magnet instead of an AlNiCo 2. Either design variations contribute to the different performance.

 

It's hard to tell if it was an intended or accidental swap. The coils of 490R and 490T are quite close - the only very distinction is in the bobbin dimensions for the different pole piece spacings. Close match of string runs delivers a cleaner, tighter tone, and this is what makes the 490R/490T combo a "modern classic" I think. In my opinion and to my taste using pickups as intended is best.

 

The "classic" Gibson humbucking pickups, the PAF family members, all have "R" spacing though. The pickups of most of my Gibson guitars belong here, and therefore the bridge pickups have "R" spacing as well as the neck and in one case middle pickups do. My avatar shows the only guitar of mine where it's the other way round - the Dirty Fingers Plus Rhythm pickup is "T" spaced as well as any other DF line humbucker including the DF Plus Lead pickup pictured. [biggrin]

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Perhaps this guitar originally came with a 498T - and someone at some point changed that pickup to a 490T. I wonder what the story is behind the pickups having their positions swapped. Accident or purposeful?

Could have been on purpose, the 490 models are very similar to '57 Classics.

Perhaps the switching from a 498T to a 490T including the position swap has been a holistic plan. Here's why I came to think so.

 

I think the creation of the 490 series pickups fulfilled two demands. First it was about classic PAF tone through close inductances and resonances. Matching string runs through close pole piece alignment brought tight response and most sustain possible with the given coil designs to either neck and bridge position.

 

Perhaps a pre-owner of this Les Paul Custom wanted to achieve the various responses to the strings through misalignment, tightest for G3rd and D4th, loosest for E1st and E6th, and in this case for both pickup positions?

 

There are so many variables in humbucker design, and string alignment is just one of them. The most common one are mismatched coils when I think of BurstBuckers, 500T, '59 Tributes and '61 Tributes. One could even use differently spaced bobbins for one humbucker to match the string spacing gradient across a single pickup position, but sideward shift through intonation adjustments of a slanted Tune-O-Matic probably would foul it up in the end... [rolleyes]

 

Some end up with rail pickups for the most even response possible. To each one's own! [biggrin]

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I'm considering buying a 489T and placing that pickup in its proper position - the bridge position. Or, maybe a 490R/498T set so that covers match. It looks like reusing my old covers would require a good bit of careful desoldering. New covers would probably look fine though.

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While searching for a 498T pickup on the Gibson site I noticed that the wire connected to the pickup is different from what's in my 1992 Les Paul. The wire for both the 490R and 498T are four conductors with insulation on the outside. On my guitar both pickups are two conductor output with a metal braid for the outer conductor.

 

 

Here are the links to the 498T and 490R pickups:

 

http://store.gibson.com/498t-hot-alnico-bridge/

 

http://store.gibson.com/490r-modern-classic-neck/

 

 

So, what do I have installed in my guitar?

 

I did a very quick ohm measurement several days ago and recall something around 8k ohms for each pickup. At that time I thought that tended to say I had a set of 490R/490T (due to spacing of the poles)

 

David

P.S. I suppose it is entirely possible that older 490R/490T or 490R/498T pickups had the single output with the exposed metal shield. True?

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...

P.S. I suppose it is entirely possible that older 490R/490T or 490R/498T pickups had the single output with the exposed metal shield. True?

Yes, definitely. They came exclusively this way many years ago.

 

I think they still make them. There are several Gibson pickups made for production guitars or basses only but not available for the aftermarket or even as spare part.

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Yes, definitely. They came exclusively this way many years ago.

 

I think they still make them. There are several Gibson pickups made for production guitars or basses only but not available for the aftermarket or even as spare part.

 

I have to admit I do like that single conductor metal braid look - However, it'd be cool (or so I think) to split the coils for added sounds. So, the four wire 490R/498T would facilitate that idea.

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The way you measured the DC resistance through the pots and a cable won't work.

Given an 8 kOhms DC pickup and a 300 kOhms volume pot, the error is circa -2.6% only. It can be further minimized through reading the maximum resistance when turning down the pot, thus determining the pot's resistance which is four times the result minus the exact pickup DC resistance. Since you don't know it, you will have to use an approximate value, but this will still reduce the error to less than +/- 0.07%.

 

You don't have to remove any cover from an electric guitar with a passive circuitry to do these measurements. I always do it this way.

 

If you want readings more exact than +/- 0.07%, you will have to invest in an ohmmeter far costlier than your guitar.

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Given an 8 kOhms DC pickup and a 300 kOhms volume pot, the error is circa -2.6% only. It can be further minimized through reading the maximum resistance when turning down the pot, thus determining the pot's resistance which is four times the result minus the exact pickup DC resistance. Since you don't know it, you will have to use an approximate value, but this will still reduce the error to less than +/- 0.07%.

 

You don't have to remove any cover from an electric guitar with a passive circuitry to do these measurements. I always do it this way.

 

If you want readings more exact than +/- 0.07%, you will have to invest in an ohmmeter far costlier than your guitar.

 

A quick calculation shows that a 440k pot in parallel with an 8k resistance will read (8)(440)/(448) = 7.86k instead of 8k - about 2% low.

 

Someone just mentioned that temperature should be considered when making a DC resistance measurement of the pickup. Originally I would not have thought of this. But, some quick and dirty calculations reveal

 

68F . . . . . .8000

95F . . . . . .8463 +5% (approx.)

115F . . . . . 8803 +10%

 

By the way, I remeasured my pickups directly at their output wires. On my guitar the pickups are swapped so the table below notes where the pickup is installed and what type of pickup it is.

 

Location of Pickup________Type of Pickup____________Resistance

neck . . . . . . . . . . . . . . . . . . . .490T . . . . . . . . . . . . . . . . . . 8228 ohms

bridge . . . . . . . . . . . . . . . . . . 490R . . . . . . . . . . . . . . . . . . 7856 ohms

 

My original DC resistance measurement was through a patch chord and, of course, that also includes parasitic resistance of the potentiometer - the wiper resistance + any additional resistance through the last leg of the potentiometer (I'll just say "wiper resistance" for brevity). I tried to compensate for this by measuring this wiper resistance with the volume pot at zero - then subtracting the error. But, this requires a symmetrical pot - that is, it requires the wiper resistance to be the same at both 10 and 0. It is not. One of the volume pots had more than double the wiper resistance at the 10 position when compared to the 0 position.

 

So, in the end, it's a lot easier to remove the cover and measure the DC resistance.

 

But, I don't feel that DC resistance alone is the best for characterizing - so I decided to add an inductance measurement. I didn't make these measurements with a bridge - just phase and magnitude - and a curve fit over a frequency range.

 

I came up with 4.4H (I only measured the 490R currently located in the bridge position of my guitar).

 

I'll probably take more measurements after finding a more accurate way and perhaps better model of the pickup. But, at this time given the resistance, inductance value, pole spacings and the fact that both of these pickups have "Gibson USA" stamped on the back I'm going to say I've got a set of 490R/490T in my guitar

 

David

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