Mods/Improvements for your G&L

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Mods/Improvements for your G&L

Postby Templar » Mon Mar 13, 2006 5:43 am

Here's Ken's superb shielding job.

Right here.

Ken...
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Jack replacement procedure

Postby Ken Baker » Mon Mar 13, 2006 9:18 pm

Here's a refreshed little ditty on replacing the jack in your L series bass.

http://www.bassesbyleo.com/jack_replacement.html

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Passive circuits with SC mode

Postby Ken Baker » Mon Mar 13, 2006 9:21 pm

Advanced coil switching and passive mode. Old & new style EQ too.

http://www.bassesbyleo.com/passive_l_series.html

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Question

Postby Cheap Bass Tard » Fri Jun 02, 2006 12:09 pm

Ken -

I really like the schematic above. It's a good "before" illustration.

But I'm not sure how it would change if I shield everything and go w/a star ground.

Obviously the green wires would all be tied together along with a wire grounding all the foil shielding, but what about the black wires that tie ground together on the 3 pots?

And would the bridge shield be tied to the jack ground or to the SPG?

Don't mean to be a numbskull, but those MFDs are sensitive and I've had noise issues in one venue that uses lots of dimmers [smilie=icon_eek.gif] and I'd like to shield my L2K and I want to get it right the FIRST time.
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Re: Question

Postby Ken Baker » Mon Jun 05, 2006 4:02 pm

Cheap Bass Tard wrote:But I'm not sure how it would change if I shield everything and go w/a star ground.


1. If all you're after is to shield the bass, there should be no change to the schematic. If there is a dark-grey paint in your cavity, you're already shielded, so don't bother.

2. Due to the way that the electronics are designed & implemented, a star ground would be nearly impossible to do. To try to force it would likely create more noise than you have now and very possibly break something. If you really have a burning desire to shield the bass, remove the knobs and nuts from the switches and pots, then carefully lift the whole assembly up to get some access to the cavity. You might have to desolder the jack to do this.

Obviously the green wires would all be tied together along with a wire grounding all the foil shielding, but what about the black wires that tie ground together on the 3 pots?

And would the bridge shield be tied to the jack ground or to the SPG?


Ideally, you want all grounds to be at the same eletrical potential, which is the purpose of a star ground. I just don't think you'd be able to get there without causing problems.

Look at it this way: The only reason this diagram exists was because I had to replace the preamp assembly. Why? Because I tried to pull it off the pots and probably broke a PCB trace. The circuit should be quiet unless you're in a very noisy environment.

Don't mean to be a numbskull, but those MFDs are sensitive and I've had noise issues in one venue that uses lots of dimmers and I'd like to shield my L2K and I want to get it right the FIRST time.


I don't think you'd cure much, if anything, by going through what you propose. Your better bet might be to:

1. Get your rig on a power conditioner.

2. Make certain that your rig is grounded well.

3. Use VERY good cables. I like Bayou Cables.

4. Limit your use of stomp boxes at noisy venues.

If you get the impression that I'm really trying to steer you away from attempting a star ground, you're right. The potential benefit is far outweighed by the risk.

Ken...
Last edited by Ken Baker on Sun Mar 04, 2007 8:47 pm, edited 1 time in total.
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Postby Cheap Bass Tard » Mon Jun 05, 2006 6:24 pm

O.K. so I assume the earlier G&Ls weren't shielded at all?

Thanks for the advice. Will look into a power conditioner since I don't use stomp boxes (yet) and I use good cables.

FWIW series/parallel and pickup selector switch settings made no diff in the amt. of hum. Suspect it was the dimmers on the can lights.
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Postby Ken Baker » Mon Jun 05, 2006 7:59 pm

Cheap Bass Tard wrote:O.K. so I assume the earlier G&Ls weren't shielded at all?


Truth be told, I don't know. My 2 L2Ks are later models and have shielding paint - that dark-grey stuff I mentioned earlier. Jim might be able to shed some light on the early ones. Still, the circuit should be inherently quiet. A noisy bass in a noisy environment can be helped, but not cured, and sometimes the hoops we jump through cause more trouble than it's worth. I'd just hate to see you go through 38 varieties of crap, only to break your bass or make no difference.

OTOH... If the bass is noisy all the time, then you could have a preamp problem. For that you get a replacement chip (if socketed) or a new board. Or, more likely, an entire preamp assembly which has all the pots & switches prewired.

Will look into a power conditioner


Be sure to check the ground at the venue as well. One of these can save you a lot of grief, and they're cheap.

Image

FWIW series/parallel and pickup selector switch settings made no diff in the amt. of hum. Suspect it was the dimmers on the can lights.


Series/parallel shouldn't make any difference because the pickups are still humbucking. Are you in fairly close proximity to the dimmers?

Ken...
Last edited by Ken Baker on Wed Feb 20, 2008 8:55 pm, edited 3 times in total.
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Postby spideyjg » Mon Jun 05, 2006 8:24 pm

Nothing but a brass plate at the bottom of the "E"

Image

The L1K was nekkid. This is during..
Image

Key thing is a good bridge ground. The G&L's have just a wire on the wood and I put tape to improve the contact. I did this on the SB-1 also.

Image

This was post shielding.

Image
The L1K was like the Climax innards at first....

Image

My '93 has paint but is still noisy active in a bad environment...
Image

The SB-1 was nekkid...
Image

Fixed it.
Image

L5K. I never shielded this one.
Image

Early L1K is like the "E"
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The El Toro is like the E and 1K but is quiet as a mouse. [smilie=coz.gif]

Image


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Last edited by spideyjg on Sun Aug 20, 2006 1:09 pm, edited 3 times in total.
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Postby Flash » Mon Jun 05, 2006 8:39 pm

They've gone back and forth with shielding but they've done it consistantly since some time around 2000. My 1997 L2500 was shielded my (early) 2000 ASAT bass was not, my 2002 JB2 (just left the herd) was. FYI - My JB2 was still noise despite the shielding until my tech added some copper foil to the back of the control cavity cover. It was silent ecver since. That could help your L2000 a bit but I suspect the dimmers have more to do with it - dimmers can be a very bad thing!!!
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Postby spideyjg » Tue Jun 06, 2006 11:04 pm

More of a technical fact than a mod.

I measured the current draw of several G&L's all were 45 microamps with a plug in the jack and no current draw unplugged. Using the Energizer amp hours as a reference a G&L will pull the battery down in about 13 months of being constantly plugged in.

The exception is the Climax drawing 200 microamps even unplugged. Unlike the other models the Climax has a jack that constantly provides the battery ground as opposed to breaking the contact when unplugged. A Climax will eat the battery about every 4 months plugged in or not. A project upcoming later is to get a switching jack in there to prolong the battery life.

I do not know if the L-1500/1505 are the same as the Climax in this regard.

Jim
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Postby spideyjg » Wed Aug 23, 2006 10:21 pm

Taking a page from Ken's book to the pimp. Notice unlike Ken's, the shielding paint on the pimp came all the way up the route for the coverplate. I probably could get away with just tape on the plate but I just got a shitload of tape. [smilie=cheeky-smiley-025.gif] [smilie=fun_84.gif]

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Spring "ping" fix method

Postby Ken Baker » Sat Sep 30, 2006 10:19 pm

Spring ping seems to be an issue with a lot of JB-2s. Maybe others - I dunno. Anyhoo, here's a method to fix it that you might find useful.

Just so's ya know, this is how my L-2000 came from the factory. It isn't my idea by any stretch, but it does work well and you don't have to worry about foam deterioration.

Run down to your friendly neighborhood auto parts store and get a piece of thin neoprene gasket material. Like 1/32" or 3/64" thin. 1/16" will be okay if it's really flexible. You might also find this sort of thing in a good plumbing supply (big box home centers don't count).

Cut strips of the stuff as long as the spring and just wide enough that it'll slip inside the spring while just clearing the sides.

Reassemble and your spring ping should be gone.

Ken...
Last edited by Ken Baker on Mon Dec 11, 2006 1:17 pm, edited 1 time in total.
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SB-2 tone pot mod

Postby Ken Baker » Sat Sep 30, 2006 10:26 pm

I'll be re-posting my pictorials and such in the near future as web pages.

Sorry for any inconvenience.

Ken...
Last edited by Ken Baker on Sun Mar 29, 2009 9:07 pm, edited 3 times in total.
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Postby Ken Baker » Thu Dec 14, 2006 10:05 am

This is part of a discussion on converting Stew-Mac's 500K Dual concentric pot to 250K.

This is a conversion used in my SB-2 tone pot mod and involved soldering a pair of 1M 1/4W resistors across the outer legs of each pot. Then people wanted to know how I got there.

Maybe this'll help:

To calculate the effective resistance of a parallel network of resistors with unequal values, we use a formula called the reciprocal of the reciprocal.

1 / (1/R1 + 1/R2 + 1/R3) = Reff

So...

The pot on the concentric pair is 500,000 (500K) ohms
The 1/4 watt resistors are 1,000,000 (1MEG) ohms

1 / 1/500,000 + 1/1,000,000 + 1/1,000,000

Which is the same as...

1 / 0.000002 + 0.000001 + 0.000001

Which is the same as...

1 / 0.000004

Which equals...

250,000

============================================

And it continues:

spideyjg wrote:OK maybe I'm thick or something Ken but if you want to drop a 500K resistor to 250K using a parallel resistor, you just slap a 500K in parallel to get 250K? Did I study the law by the other ohm brother?



Guess I shoulda 'splained why it gets done with a pair of 1 meggers.

A single 500K resistor would work fine if such a critter existed, but they don't. 500K is a non-standard value that would be effectively impossible to find. The nearest standard values are 470K and 520K. Don't ask me why. It doesn't make a bit of sense to me either.

As odd as 470K and 520K sound, an even 1 meg ohm is a standard value. So we do a parallel pair of them for an effective 500K, which yields 250K when connected in parallel with another 500K resistor or pot. For this particular application, the 1/4 watt resistors fit perfectly and tuck in out of the way nicely.

spideyjg wrote:Or is the set of 1 megs to get the "audio taper" which I honestly don't know the ins and outs of.



Audio taper, or log taper, pots were designed to be volume controls because we measure sound levels in decibels. Decibel scales are logarithmic, as opposed to linear. If a fixed value resistor is connected to the resistance pad of a pot, either in series or parallel, the curve will be affected. How much depends on the value of the fixed resistor. There. I've said enough to get into trouble.

As I mentioned in the SB-2 text, this will NOT give you a perfect audio taper. OTOH, it doesn't end up to be a linear taper either. Kinda-sorta someplace in between, but more to the audio taper feel. It does work very well as a volume control. Close enough for rock & roll and my ear!

Ken...
Last edited by Ken Baker on Thu Dec 14, 2006 3:56 pm, edited 1 time in total.
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Postby Ken Baker » Thu Dec 14, 2006 10:08 am

This is part of a discussion of converting a Stew-Mac 500K dual concentric pot to 250K/1M

Is there a way to convert a 500k/500k stackpot into a 250K/1meg, so can use it as a stacked t/b control?


Taking a 500K pot and reducing its value is, as noted above in this thread, a simple matter of networking in parallel resistance. You just have to remember that the curve will not be precise; but while the curve isn't pretty, the pot/resistor combo will still vary resistance from zero ohms to whatever its modded value is.

Increasing the value would mean adding resistance in series with the pot, which means that the max value will be as you want it. However, when you crank back the pot completely, the least resistance it will show the circuit will be the value of the resistor you added in series. It will not reduce resistance to zero ohms as it would if the series-connected resistor weren't there.

Ken...
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