Les Paul Studio - desolder problems

[mark surridge]

I have a very nice LP Studio in the work shop with a ground hum, i.e. The hum stops when grounding out the strings. First I checked for continuity with the multi meter and that all seems fine.I decided to resolder all the ground connections to make sure the ground loop was working correctly but I am unable to desolder the joints, I believe this is because they are now using lead free solder. After some research I tried mixing in some old school solder with the lead free and tried to suck up the solder but no luck. I have tried 5 different irons so far, up to my 100W gun but still cannot get the lead free to flow. Any advice would be welcome.

[Greg Robinson]

Hi Mark,

I always like to add a bit of fresh solder when trying to re-flow any old solder joints, particularly lead-free ones (ROHS). The trick is to introduce the solder between the joint and the iron tip.
Is the solder flowing on the tip?
Is the tip clean and shiny?
Are you using rosin core solder?
Have you tried using extra flux?
Is the tip you are using a good fit for your iron?

By the way, when you say "The hum stops when out grounding the strings.", do you mean the strings are un-grounded, or do you mean that the hum stops when you touch the strings? If the later, that is normal behavior, the human body radiates quite a lot of electromagnetic radiation, and grounding yourself to the strings alleviates the interference it causes, humbuckers are more prone to this than single coils due to their higher inductance.

Also, is this the original LP studio with the low impedance pickups, or a later reissue with standard pickups?

[Mark Swanson]

And does it have P-90's? They always hum. If the wiring is stock, it is likely that there is nothing wrong with it. See this discussion http://www.mimf.com/phpbb/viewtopic.php?f=10&t=1045
And I would guess that you are not getting enough heat to the solder joint. If you are soldering on the back of the pots, that takes quite a bit of heat.

[David King]

There are some really burly lead free solders out there that seem to need an 800º iron to budge. I just got a new 100w Weller pencil but it only heats to 700 and it won't do much for me even with the fattest tip installed.

There is a special solder additive that dramatically lowers the melting temp of most alloys. It's called lowmelt http://www.zeph.com/lowmelt.htm

I wouldn't mix lead and lead-free formulations as a habit or you may develop "tin whiskers" over time which can short out connections.

[mark surridge]

The guitar is a reissue with humbuckers, not P90's. When I touch the strings the hum stops. I have checked the ground from the tailpiece and that is fine. There are a couple of joints that look 'cloudy' instead of bright, which suggests to me that the soldering may not be all it should be. I have done some net research and there are several instances of this same problem. It seems most people just live with the hum but I do not find that very satisfactory.

[Greg Robinson]

The only way to eliminate this problem is to get extremely well balanced humbuckers (but such humbuckers will generally sound "lifeless" and have reduced high-frequency response), or to use low impedance pickups, preferably active.
Part of learning to play electric guitar is to master the technique of always keeping your hand in contact with the strings or bridge, to avoid this hum.

[Mark Swanson]

Use a VOM or a multimeter to check for continuity on all the grounds. If the meter tells you they are connected, then they are and reheating them won't make a bit of difference. Cloudy or not, I still think there is nothing wrong with your ground connections.

[David King]

I've heard of folks rewinding with different gauge windings at equal turns count for each coil to keep the hum canceling while maintaining the brightness of offset coils. Typically they'd use 5k turns of 43 and 42 (or 44 if the 42 won't fit)
Why not just use a grounding strap to the wrist if it's a critical studio situation?

[David Schwab]

This is NOT hum, it's buzz. Humbuckers cancel out magnetic field noise, which is hum. What you are hearing here is electrical field noise. It has nothing to do with the pickups. This is fixed with shielding. Also, sometimes the ground wiring in your house, or even in the amp isn't so great, and you get buzzing. This also has nothing to do with a ground loop, which is not possible to have in a guitar since it only has a single ground at the output jack. Ground loops are caused by two different ground potentials.

Is the control cavity shielded?