Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Default Gibson Les Paul

Output from guitar noticeably dropped in level , owner had a spare one to
complete the set. When I received it , setting both vol pots to minimum then
ohmage across output was 30 ohm. Now I'm inside, it is 3 to 5 ohms according
to switch setting. Pickup ohmages measure 7.82,3.80, 7.39K at the 3 switch
settings, which seems right, and consistent with wire tugs.
Now the bottom ohmage of the pots was not going to be 60 and 60 ohm or so to
give 30, one poor pot perhaps. I will remove the output screened lead
although nothing seems wrong with it, but the output socket was loose and
turning to an extentm requiting the screened lead to resist the turning.
Just leaves wear /plating problem at the tip contact of the switchcraft 1/4
in socket but it looks perfectly normal, contact point axial to jack until
deflected to the tip groove , etc. Pots measure consistent across tracks.
Switch seems ok but how to test other than by replacement


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"N_Cook" wrote in message
...
Output from guitar noticeably dropped in level , owner had a spare one to
complete the set. When I received it , setting both vol pots to minimum
then
ohmage across output was 30 ohm. Now I'm inside, it is 3 to 5 ohms
according
to switch setting. Pickup ohmages measure 7.82,3.80, 7.39K at the 3 switch
settings, which seems right, and consistent with wire tugs.
Now the bottom ohmage of the pots was not going to be 60 and 60 ohm or so
to
give 30, one poor pot perhaps. I will remove the output screened lead
although nothing seems wrong with it, but the output socket was loose and
turning to an extentm requiting the screened lead to resist the turning.
Just leaves wear /plating problem at the tip contact of the switchcraft
1/4
in socket but it looks perfectly normal, contact point axial to jack until
deflected to the tip groove , etc. Pots measure consistent across tracks.
Switch seems ok but how to test other than by replacement




Check the output socket signal connection and all pot solder connectors are
not touching their pot bodies or any conductive screening paint, if there is
any, or any stray strands of screening braid.
Check the tone control pot caps are not being shorted to themselves or pot
body as things move and turn.

Not sure why you are particularly interested in the values of the pots at
zero, it is their values at max that you need to be looking at.

Or it could have been a problem with the jack lead or amp and not the guitar
at all.



Gareth.

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Default Gibson Les Paul



"N_Cook" wrote in message
...
Output from guitar noticeably dropped in level , owner had a spare one to
complete the set. When I received it , setting both vol pots to minimum
then
ohmage across output was 30 ohm. Now I'm inside, it is 3 to 5 ohms
according
to switch setting. Pickup ohmages measure 7.82,3.80, 7.39K at the 3 switch
settings, which seems right, and consistent with wire tugs.
Now the bottom ohmage of the pots was not going to be 60 and 60 ohm or so
to
give 30, one poor pot perhaps. I will remove the output screened lead
although nothing seems wrong with it, but the output socket was loose and
turning to an extentm requiting the screened lead to resist the turning.
Just leaves wear /plating problem at the tip contact of the switchcraft
1/4
in socket but it looks perfectly normal, contact point axial to jack until
deflected to the tip groove , etc. Pots measure consistent across tracks.
Switch seems ok but how to test other than by replacement




Oh, and sometimes the guitar pickup coils become damaged either by the pick
hitting it, or by sweat ingress, and intermittently or permanently lose one
winding.


Gareth.

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Default Gibson Les Paul

Gareth Magennis wrote in message
...


"N_Cook" wrote in message
...
Output from guitar noticeably dropped in level , owner had a spare one

to
complete the set. When I received it , setting both vol pots to minimum
then
ohmage across output was 30 ohm. Now I'm inside, it is 3 to 5 ohms
according
to switch setting. Pickup ohmages measure 7.82,3.80, 7.39K at the 3

switch
settings, which seems right, and consistent with wire tugs.
Now the bottom ohmage of the pots was not going to be 60 and 60 ohm or

so
to
give 30, one poor pot perhaps. I will remove the output screened lead
although nothing seems wrong with it, but the output socket was loose

and
turning to an extentm requiting the screened lead to resist the turning.
Just leaves wear /plating problem at the tip contact of the switchcraft
1/4
in socket but it looks perfectly normal, contact point axial to jack

until
deflected to the tip groove , etc. Pots measure consistent across

tracks.
Switch seems ok but how to test other than by replacement




Oh, and sometimes the guitar pickup coils become damaged either by the

pick
hitting it, or by sweat ingress, and intermittently or permanently lose

one
winding.


Gareth.


Tugging on the screen leads to the pickups did not change the DC ohmages so
I left them be and all those adjustments . From the 8 figure serial number
this was probably mid 2003 but I doubt Gibson would use computer data cable
to the switch, presumably someone replaced it. The foil sheathing of that,
at the end, was floating in space and could have touched the signal out
line, The "cloth" core of the sig out wire was disrupted where the earthing
braid is soldered to the switchcraft socket and being loose, turned.
As turning a jack in there, there was a poor-conductive point to the contact
so perhaps a build up of sprayed in WD40 leading to that and a bit of
conduction at the core fraying.
If I owned one of these I'd ditch that silly plastic output escutchion and
replace with a brass plate and 4 larger screws. Hairline stress cracks to
each of the 4 mounting holes in that plastic and will fail soon - all the
guitar lead yanking having to be restrained by that plastic square along
with the bush nut localised stress.


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Default Gibson Les Paul

You might try identifying the model of the guitar to be able to find out
more about it.
The serial number only reveals the production date, factory location and
production number.. not the model number.

There are numerous sources of original wiring diagrams online.. then there
are modified wiring arrangements (splitting coils, phase reverse etc) also
methods to replicate the 1950s type wiring methods.

The genuine Gibson brand Les Paul models generally have 2 pickups, fewer
have 3, but there numerous Les Paul models.

The Vol and Tone pots would've originally been 500k.. although some prefer
to replace them with 250k.
Many users believe they'll sound much better if they modify the wiring and
replace components with parts of different values.

There are a lot of amateur repairs and attemts to upgrade parts floating
around, and sometimes attempted by hobbiests who don't understand wiring
diagrams or proper techniques.
The computer cable you discovered is an example of the *any wire will work*
attitude of the inexperienced.

The 7k+ ohm readings you mentioned seem normal (aftermarket humbuckers can
read as high as around 15k ohm), but the 3.80k isn't a typical humbucker
reading unless the separate internal coils are connected in parallel, which
is fairly easy to do if the pickup has a 4-wire lead (whether that would be
the original wiring for that pickup is unclear).

Some paralleled coil or other special/modified features are attained by
using a push-pull switch integrated into one of the control pots.

--
Cheers,
WB
..............


"N_Cook" wrote in message
...
Output from guitar noticeably dropped in level , owner had a spare one to
complete the set. When I received it , setting both vol pots to minimum
then
ohmage across output was 30 ohm. Now I'm inside, it is 3 to 5 ohms
according
to switch setting. Pickup ohmages measure 7.82,3.80, 7.39K at the 3 switch
settings, which seems right, and consistent with wire tugs.
Now the bottom ohmage of the pots was not going to be 60 and 60 ohm or so
to
give 30, one poor pot perhaps. I will remove the output screened lead
although nothing seems wrong with it, but the output socket was loose and
turning to an extentm requiting the screened lead to resist the turning.
Just leaves wear /plating problem at the tip contact of the switchcraft
1/4
in socket but it looks perfectly normal, contact point axial to jack until
deflected to the tip groove , etc. Pots measure consistent across tracks.
Switch seems ok but how to test other than by replacement





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"Wild_Bill"


** Top posters are all ****wits.


The 7k+ ohm readings you mentioned seem normal (aftermarket humbuckers can
read as high as around 15k ohm), but the 3.80k isn't a typical humbucker
reading



** Middle switch position = pickups in parallel.



.... Phil



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Default Gibson Les Paul

The 7k+ ohm readings you mentioned seem normal (aftermarket humbuckers can
read as high as around 15k ohm), but the 3.80k isn't a typical humbucker
reading unless the separate internal coils are connected in parallel,
which is fairly easy to do if the pickup has a 4-wire lead (whether that
would be the original wiring for that pickup is unclear).



These reading, according to the OP, were at the switch position, where the
centre position would be the two humbuckers in parallel.

Thus, 3.8k is pretty much as expected.




Gareth.

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Default Gibson Les Paul

One thing's for sure.. interpreting Nigel's posts ain't easy. At least he
has some comments to proceed with.

--
Cheers,
WB
..............


"Gareth Magennis" wrote in message
...
The 7k+ ohm readings you mentioned seem normal (aftermarket humbuckers
can read as high as around 15k ohm), but the 3.80k isn't a typical
humbucker reading unless the separate internal coils are connected in
parallel, which is fairly easy to do if the pickup has a 4-wire lead
(whether that would be the original wiring for that pickup is unclear).



These reading, according to the OP, were at the switch position, where the
centre position would be the two humbuckers in parallel.

Thus, 3.8k is pretty much as expected.




Gareth.


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Default Gibson Les Paul

Wild_Bill wrote in message
...
You might try identifying the model of the guitar to be able to find out
more about it.
The serial number only reveals the production date, factory location and
production number.. not the model number.

There are numerous sources of original wiring diagrams online.. then there
are modified wiring arrangements (splitting coils, phase reverse etc) also
methods to replicate the 1950s type wiring methods.

The genuine Gibson brand Les Paul models generally have 2 pickups, fewer
have 3, but there numerous Les Paul models.

The Vol and Tone pots would've originally been 500k.. although some prefer
to replace them with 250k.
Many users believe they'll sound much better if they modify the wiring and
replace components with parts of different values.

There are a lot of amateur repairs and attemts to upgrade parts floating
around, and sometimes attempted by hobbiests who don't understand wiring
diagrams or proper techniques.
The computer cable you discovered is an example of the *any wire will

work*
attitude of the inexperienced.

The 7k+ ohm readings you mentioned seem normal (aftermarket humbuckers can
read as high as around 15k ohm), but the 3.80k isn't a typical humbucker
reading unless the separate internal coils are connected in parallel,

which
is fairly easy to do if the pickup has a 4-wire lead (whether that would

be
the original wiring for that pickup is unclear).

Some paralleled coil or other special/modified features are attained by
using a push-pull switch integrated into one of the control pots.

--
Cheers,
WB
.............



If they did not compress the braid of the screening , before soldering ,
then there would be less likelihood of problems with that old-style
lacquered "hosiery" cloth insulation.
Perhaps like the plastic escutchion, deliberate built-in pitfalls, having no
justification otherwise


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