Troubleshooting A Standard Stratocaster™ Guitar
First, if you got here via a link from anywhere other than the troubleshooting menu
please go there first for information you will need to apply these instructions safely and
effectively!
This troubleshooting guide will take you step-by-step through troubleshooting a Stratocaster™ guitar that
is set up for "standard" five-way switching. That is, the guitar has a single volume control, 0 to 2 tone
controls, and a five way switch that, from rearmost to frontmost selects the bridge pickup, the bridge and middle
pickups in parallel, the middle pickup, the middle and neck pickups in parallel, and the neck pickup.
There are two troubleshooting tables, one using no special equipment and one requiring an inexpensive ohmmeter.
There is a lot of overlap between the tables, i.e. both tables will detect and identify most conditions.
There are a few conditions which may not show up with a meter (such as microphonic pickups). However, the
meter tests in the second table will often isolate symptoms to a specific component
where the "no equipment" test can only narrow the causes down any of several components. In short, both
tables are useful and even if you have a meter you shouldn't necessarily ignore the first table. Likewise,
if you don't have a meter and the first table only isolates the problem to one of several components it
may be worth your while to purchase an inexpensive meter.
The second table also works as a fairly comprehensive sanity check – that is, after working on a guitar you
can run through those tests after reinstalling the pickguard but before restringing the guitar to confirm that
you got all of the pickup wires on the right switch terminals, didn't reverse the output jack wires, and so on.
I do these checks routinely and it's saved me having to waste time stringing and unstringing a guitar on a couple
of occasions.
All of the tests can be run without removing the pickguard. The tests in this first table can be run without
any test equipment, using only your guitar and an amplifier. Often one problem may have several symptoms, so
run through the entire test and note the possible causes mentioned for each bad result you observe. If you have
two or three different symptoms, and all share one possible cause, that is most likely the problem.
| Table I – No-Equipment Tests |
| For this test plug your guitar into your amplifier and turn the gain on your amplifier
up fairly high (about as high as you would normally play if you didn't have to worry about getting
kicked out of your apartment). Turn off all effects including reverb and noise gates.
Sit facing the amp and approximately four to six feet away from it.
Work your way from top to bottom down the table, setting the controls and taking the actions specified,
then observing the results and matching them with the results column. Read the possible causes
for abnormal results from the possible causes column in the same row as the observed result.
Be prepared to quickly turn down the volume if you encounter feedback squeal. |
| Conditions |
| Volume | Tone 1 | Tone 2 | Switch | Action | Result | Likely Causes |
| Fully On (CW) |
Fully Up (CW) |
Fully Up (CW) |
Bridge |
Do not touch any metal parts on the guitar. |
Pretty quiet, but not "dead." |
Normal if guitar is well shielded or has humbucking pickups. |
| Loud hum, but no squeal. (Assuming you have determined that the hum is caused
by the guitar, and not by some other problem.) |
Fairly normal, for an unshielded guitar with single coil pickups. Consider
shielding using the "Quieting the Beast" instructions. |
| Completely dead. |
Try lightly flicking a string, if there is still no sound then the pickup, switch,
volume pot, jack, or any of the interconnecting wiring may be bad. If the remaining steps in
this table reveal that other switch positions are okay then the problem must be the bridge pickup,
the switch, or the wiring associated with the bridge pickup. |
| Feedback squeal. |
Lightly mute the strings, then carefully remove your hand without disturbing
the strings. If the squeal remains or returns then the bridge pickup is badly microphonic,
check mounting springs, pot the pickup or replace it if necessary. |
| Lightly touch the strings with your bare hand. |
Noise gets quieter. |
Normal. |
| Noise gets louder. |
The strings may not be grounded, in the case of a stock guitar this means there is probably a broken
or missing ground wire to the tremelo claw. On a guitar with an isolation capacitor the capacitor may
be of too small a capacitance or the capacitor may be open.
Another possible cause is that the signal and ground wires to the jack have been reversed. |
| While lightly damping all strings with your hand, gently tap the
bridge pickup with a pencil or pick. |
Clicking sound in amp. |
Normal. |
| Loud clunking or clicking sound that transitions to a feedback squeal. |
Bridge pickup is microphonic, check mounting springs, pot the pickup or replace
it if necessary. |
| Gently wiggle the pickup switch from side to side and even fore and
aft (but not enough to move it out of the bridge detent). |
No Noise. |
Normal. |
| Clicking, popping, or scratching sounds. |
Switch is dirty, worn, or of poor quality and may require replacement soon. |
| Only if you have TBX (bridge) tone control.
Rotate the mid/bridge tone control slowly back and forth from stop to stop, leave it in the fully up
position. |
No Noise. |
Normal. |
| Clicking, popping, or scratching sounds. |
Tone pot is dirty, worn, or of poor quality and may require replacement soon. |
| Only if you have TBX (bridge) tone control.
Play a chord, then rotate the mid/bridge tone control back and forth from stop to stop, leave it in the fully up
position. |
Tone changes. |
Normal. |
| Tone does not change. |
TBX portion of tone control is defective or has been disabled (a lot of people don't
like the TBX tone controls). |
| Fully On (CW) |
Fully Up (CW) |
Fully Up (CW) |
Middle |
Do not touch any metal parts on the guitar. |
Pretty quiet, but not "dead." |
Normal if guitar is well shielded or has humbucking pickups. |
| Loud hum, but no squeal. (Assuming you have determined that the hum is caused
by the guitar, and not by some other problem.) |
Fairly normal, for an unshielded guitar with single coil pickups. Consider
shielding using the "Quieting the Beast" instructions. |
| Completely dead. |
Try lightly flicking a string, if there is still no sound then the pickup, switch,
volume pot, jack, or any of the interconnecting wiring may be bad. If the remaining steps in
this table reveal that other switch positions are okay then the problem must be the middle pickup,
the switch, or the wiring associated with the middle pickup. |
| Feedback squeal. |
Lightly mute the strings, then carefully remove your hand without disturbing
the strings. If the squeal remains or returns then the middle pickup is badly microphonic,
check mounting springs, pot the pickup or replace it if necessary. |
| While lightly damping all strings with your hand, gently tap the
middle pickup with a pencil or pick. |
Clicking sound in amp. |
Normal. |
| Loud clunking or clicking sound that transitions to a feedback squeal. |
Middle pickup is microphonic, check mounting springs, pot the pickup or replace
it if necessary. |
| Gently wiggle the pickup switch from side to side and even fore and
aft (but not enough to move it out of the middle detent). |
No Noise. |
Normal. |
| Clicking, popping, or scratching sounds. |
Switch is dirty, worn, or of poor quality and may require replacement soon. |
|
Rotate the middle tone control slowly back and forth from stop to stop, leave it in the fully up
position. |
No Noise. |
Normal. |
| Clicking, popping, or scratching sounds. |
Tone pot is dirty, worn, or of poor quality and may require replacement soon. |
|
Play a chord, then rotate the middle tone control back and forth from stop to stop, leave it in the fully up
position. |
Tone changes, volume only changes slightly or not at all. |
Normal. |
| Tone does not change. |
Bad tone pot, tone capacitor, pickup selector switch, or associated wiring (or a
previous owner may have moved the middle tone control to the bridge). Note that on an unmodified
Strat™ if both tone controls are inoperative the most likely cause is the tone capacitor or the
connections from the tone capacitor to the pots and ground (because both tone pots share one tone
capacitor). |
| Volume decreases substantially as tone is turned down, tone may or may not change. |
Shorted tone capacitor or tone capacitor far too large. |
| Fully On (CW) |
Fully Up (CW) |
Fully Up (CW) |
Neck |
Do not touch any metal parts on the guitar. |
Pretty quiet, but not "dead." |
Normal if guitar is well shielded or has humbucking pickups. |
| Loud hum, but no squeal. (Assuming you have determined that the hum is caused
by the guitar, and not by some other problem.) |
Fairly normal, for an unshielded guitar with single coil pickups. Consider
shielding using the "Quieting the Beast" instructions. |
| Completely dead. |
Try lightly flicking a string, if there is still no sound then the pickup, switch,
volume pot, jack, or any of the interconnecting wiring may be bad. If the remaining steps in
this table reveal that other switch positions are okay then the problem must be the neck pickup,
the switch, or the wiring associated with the neck pickup. |
| Feedback squeal. |
Lightly mute the strings, then carefully remove your hand without disturbing
the strings. If the squeal remains or returns then the neck pickup is badly microphonic,
check mounting springs, pot the pickup or replace it if necessary. |
| While lightly damping all strings with your hand, gently tap the
neck pickup with a pencil or pick. |
Clicking sound in amp. |
Normal. |
| Loud clunking or clicking sound that transitions to a feedback squeal. |
The neck pickup is microphonic, check mounting springs, pot the pickup or replace
it if necessary. |
| Gently wiggle the pickup switch from side to side and even fore and
aft (but not enough to move it out of the neck detent). |
No Noise. |
Normal. |
| Clicking, popping, or scratching sounds. |
Switch is dirty, worn, or of poor quality and may require replacement soon. |
|
Rotate the neck tone control slowly back and forth from stop to stop, leave it in the fully up
position. |
No Noise. |
Normal. |
| Clicking, popping, or scratching sounds. |
Tone pot is dirty, worn, or of poor quality and may require replacement soon. |
|
Play a chord, then rotate the neck tone control back and forth from stop to stop, leave it in the fully up
position. |
Tone changes, volume only changes slightly or not at all. |
Normal. |
| Tone does not change. |
Bad tone pot, tone capacitor, pickup selector switch, or associated wiring. Note that on an unmodified
Strat™ if both tone controls are inoperative the most likely cause is the tone capacitor or the
connections from the tone capacitor to the pots and ground (because both tone pots share one tone
capacitor). |
| Volume decreases substantially as tone is turned down, tone may or may not change. |
Shorted tone capacitor or tone capacitor far too large. |
| Fully On (CW) |
Fully Up (CW) |
Fully Up (CW) |
Any |
Lightly mute the strings with your hand. Rotate the volume pot slowly
back and forth from stop to stop. |
No noise. |
Normal. |
| Scratching, popping, or crackling noises. |
The volume pot is worn, dirty, or of poor quality and will probably need to be
replaced soon. |
| Play and sustain a chord. Rotate the volume pot from full on to full off. |
Volume goes smoothly and gradually from full volume to complete abscence of signal
(most hum - if any - may also disappear but there may still be some ambient noise from the cabling
and such). There is little or no change in the tone. |
Normal. |
| Volume drops raggedly, in steps. |
The pot is damaged or there may be a piece of solder, wire, etc. loose inside the pot. |
| Volume seems to do little or nothing through most of its travel then the volume changes
very suddenly. |
The pot may be damaged but it is more likely that someone has replaced it with a linear,
instead of audio taper, pot. If the control also works backwards it is likely that someone has
used the correct audio taper pot but reversed the wires on the + and - terminals of the pot.
The tests in the next table can be used
to determine which of these is causing the problem. |
| Volume never goes completely to zero-signal. |
This may be a defective pot (some cheap ones don't go to full electrical limits).
It may also mean that the ground wire on the pot is not connected or, if an isolation capacitor has
been installed, that the volume pot ground and jack ground are on opposite leads of the isolation
capacitor (i.e. the capacitor was not installed properly). The tests in the next table can be used
to determine which of these is causing the problem. |
| Tone gets dull as soon as the volume pot is backed a little off from full on. |
Usually this means you are feeding too low an impedance. This can be caused by
a long (greater than 10' cheap or greater than 25' quality) guitar cord or by feeding a low impedance
gain stage (such as by trying to run to a low-z input on a mixer or to some effects, especially vintage
Wah and fuzz pedals). This can sometimes be fixed by putting a .001uf capacitor across the plus
and wiper terminals of the volume pot. However, it is better to eliminate the true cause by
replacing the cord with a shorter, higher quality one, using an eq or gain boost effect with a high-z
input as your first gain stage, and so on. |
| Play and sustain a chord.
Move the pickup selector slowly back and forth through it's entire range. |
Tone changes with each position relative to adjacent positions. There are no
"dead spots," loud pops or crackles, etc. |
Normal. |
| In both of the mixed positions (neck/mid and mid/bridge) most of the hum (if any)
goes away. |
Normal. (Note, on early guitars and true reissues of them, the middle
pickup was not humcancelling with the other pickups – on such guitars the tone will be as expected
but the hum will not decrease in these positions.) |
| In both of the mixed positions (neck/mid and mid/bridge) the signal gets very
weak or "thin" and the hum may or may not get louder. |
The middle pickup is wired out of phase with the others. |
| In only the neck/mid position the signal gets very
weak or "thin" and the hum may or may not get louder. |
The neck pickup is wired out of phase with the middle. |
| In only the mid/bridge position the signal gets very
weak or "thin" and the hum may or may not get louder. |
The bridge pickup is wired out of phase with the middle. |
| Tone and volume are normal in all positions but only the neck/middle combination
is hum cancelling – the middle/bridge is not hum cancelling. |
Assuming all pickups are single coils, the neck and middle pickups should be swapped
so both mixed positions will be hum cancelling. If the bridge pickup is a humbucker, this
behaviour is normal. |
| Tone in one or both of the mixed positions (neck/mid or mid/bridge) does not change at all
from one of the adjacent positions. There may or may not be a "dead spot" between the positions. |
If all of the pickups passed their individual tests above, this almost has to be a defective
switch. Keep in mind that this applies only to stock guitars with Standard switches. If someone
has replaced the switch with a "Super switch", "Mega switch," or other custom wiring there may indeed be
dead spots and, depending on how the mod was wired, adjacent positions may not differ that much tonally.
The tests in the next table may
help determine which of these is causing the problem. |
| Crackling, scratching noises as the switch is moved. |
The switch is probably dirty, of poor quality, or worn.
Plan to replace it soon. |
| Popping sounds. |
This usually won't happen with a stock guitar with a standard switch. If it does
happen the switch may be bad, or someone may have altered the wiring in some manner. With custom
switches and especially with onboard preamps and active tone controls a soft pop isn't unusual. Such
a pop can usually be eliminated or greatly reduced but it takes a bit of experimentation to find and eliminate
the cause of the pop without altering the tone too drastically. |
The next series of tests requires an ohmmeter or multimeter. You needn't have an expensive meter – in
fact I strongly recommend an inexpensive analog meter similar to the one below for these tests. That
is because you can "see" capacitance and glitchy pots on such a meter better than on a digital meter.
Notice that this table also contains an extra set of "result" and "cause" columns. One set is for a stock
unmodified standard Strat and the second column is for a Strat that has been modified using the "Quieting the
Beast" modification (see the modifications in the wiring section). Where the second pair of columns is
empty the expected results and causes are identical to those for a stock unmodified Strat.
Also notice the abscence of the first three columns, for the volume and tone controls. The initial condition
for all of the tests in this table are that the volume and tone controls are fully "up" (CW).
| Table II – Ohmmeter Tests |
For this test unplug your guitar from the amplifier. If you have spare 1/4" mono
plug laying around, remove the back shell and put the plug in the output jack of the guitar. If you
don't have a spare unused plug, but do have a cord with removable shells on the plugs (i.e. not heatshrunk)
then loosen the shell from one plug and put that plug in the guitar. If all you have is a cord with
heatshrink over the plugs then plug one end of the cord into the guitar and use the free end to connect the
meter leads when necessary. The goal of all of this is to be able to put meter leads on the hot
and ground terminals of the output jack without touching any metal parts (because your body will alter
the resistance reading substantially).
If you are going to be doing much of this then alligator clips are very handy. Even better is a
short test cable with a 1/4" mono plug on one end and banana (or pin, depending on your meter) plugs
on the other.
Work your way from top to bottom down the table, setting the controls and taking the actions specified,
then observing the results and matching them with the results column. Read the possible causes
for abnormal results from the possible causes column in the same row as the observed result.
Initial conditions for all tests are volume, tone 1, and tone 2 all fully "up" (CW), and the
meter set to read 0 to 20k (20,000) ohms. Remember to return the controls to this position at
the completion of each step.
If
you are using a meter that has a "zero" adjustment for the ohms function, adjust the meter to read zero while the
probes are shorted together. Note that most digital meters don't have a zero adjustment and they
will often read an ohm or two with the leads shorted together
Some, but very few, pickups have built in inline capacitors that invalidate these tests. If
a pickup reads "open" on the meter but you are getting normal sound from it, you probably have such a
pickup. Also, note that these tests don't apply if you have active pickups, a preamp, or active
tone controls.
|
| Unmodified | Shielded & Isolated |
| Switch | Action | Result | Likely Causes | Result | Likely Causes |
| Bridge |
Measure between the two terminals of the output (DC resistance of the bridge pickup). |
Between approximately 4k and 18k ohms (typically about 5k-7k for most single coils and 9k-15k for
most humbuckers).
Write the value here ________. |
Normal. |
ditto |
ditto |
| Very close to zero. |
Shorted pickup, shorted volume pot, shorted jack wiring. |
ditto |
ditto |
| Very high, but not open (approximately 250k to 500k). |
Open pickup coil, bad switch, broken wiring between pickup and switch. |
ditto |
ditto |
| Open (greater than 2 Meg). |
Bad wiring between volume pot and jack, or bad volume pot. |
ditto |
ditto |
|
|
Meter reads very high (approximately 250k to 500k) (note, this
is most easily seen on a cheap analog meter). Reversing the meter leads causes the meter needle
to dip then climb again. |
The ground side of the pickup is attached to shield ground, instead of signal ground
(i.e. the wrong side of the isolation capacitor). |
|
|
Meter starts low, then climbs to open (greater than 2 Meg). (note, this
is most easily seen on a cheap analog meter). Reversing the meter leads causes the meter needle
to dip and then climb again. |
The isolation capacitor is in series with the signal, most likely between the negative
terminal of the volume pot and the negative terminal of the jack. |
| Middle |
Measure between the two terminals of the output (DC resistance of the middle pickup). |
Between approximately 4k and 18k ohms (typically about 5k-7k for most single coils and 9k-15k for
most humbuckers). Write the value here ________. |
Normal. |
ditto |
ditto |
| Very close to zero. |
Shorted pickup, shorted volume pot, shorted jack wiring. |
ditto |
ditto |
| Very high, but not open (approximately 250k to 500k). |
Open pickup coil, bad switch, broken wiring between pickup and switch. |
ditto |
ditto |
| Open (greater than 2 Meg). |
Bad wiring between volume pot and jack, or bad volume pot. |
ditto |
ditto |
|
|
Meter reads very high (approximately 250k to 500k) (note, this
is most easily seen on a cheap analog meter). Reversing the meter leads causes the meter needle
to dip then climb again. |
The ground side of the pickup is attached to shield ground, instead of signal ground
(i.e. the wrong side of the isolation capacitor). |
|
|
Meter starts low, then climbs to open (greater than 2 Meg). (note, this
is most easily seen on a cheap analog meter). Reversing the meter leads causes the meter needle
to dip and then climb again. |
The isolation capacitor is in series with the signal, most likely between the negative
terminal of the volume pot and the negative terminal of the jack. |
| Neck |
Measure between the two terminals of the output (DC resistance of the neck pickup). |
Between approximately 4k and 18k ohms (typically about 5k-7k for most single coils and 9k-15k for
most humbuckers). Write the value here ________. |
Normal. |
ditto |
ditto |
| Very close to zero. |
Shorted pickup, shorted volume pot, shorted jack wiring. |
ditto |
ditto |
| Very high, but not open (approximately 250k to 500k). |
Open pickup coil, bad switch, broken wiring between pickup and switch. |
ditto |
ditto |
| Open (greater than 2 Meg). |
Bad wiring between volume pot and jack, or bad volume pot. |
ditto |
ditto |
|
|
Meter reads very high (approximately 250k to 500k) (note, this
is most easily seen on a cheap analog meter). Reversing the meter leads causes the meter needle
to dip then climb again. |
The ground side of the pickup is attached to shield ground, instead of signal ground
(i.e. the wrong side of the isolation capacitor). |
|
|
Meter starts low, then climbs to open (greater than 2 Meg). (note, this
is most easily seen on a cheap analog meter). Reversing the meter leads causes the meter needle
to dip and then climb again. |
The isolation capacitor is in series with the signal, most likely between the negative
terminal of the volume pot and the negative terminal of the jack. |
| Neck & Middle |
Measure between the two terminals of the output (parallel DC resistance of
the neck and middle pickups). |
Approximately equal to (neck_resistance X
middle_resistance) divided by (neck_resistance + middle_resistance). |
Normal. |
ditto |
ditto |
| Approximately the resistance of the neck pickup. |
If the middle pickup passed its solo test above, this can only be a defective or
non-standard switch. |
ditto |
ditto |
| Approximately the resistance of the middle pickup. |
If the neck pickup passed its solo test above, this can only be a defective or
non-standard switch. |
ditto |
ditto |
| Very high, but not open (approximately 250k to 500k). |
This would have to be a bad switch or else both pickups or wiring from
both pickups to switch would have to be bad. If both pickups passed their solo tests above then
this can only be a bad or nonstandard switch. |
ditto |
ditto |
| Open (greater than 2 Meg). |
Bad wiring between volume pot and jack, or bad volume pot. |
ditto |
ditto |
|
|
Meter reads very high (approximately 250k to 500k) (note, this
is most easily seen on a cheap analog meter). Reversing the meter leads causes the meter needle
to dip then climb again. |
The ground side of both pickups are attached to shield ground, instead of signal ground
(i.e. the wrong side of the isolation capacitor). |
|
|
Meter starts low, then climbs to open (greater than 2 Meg). (note, this
is most easily seen on a cheap analog meter). Reversing the meter leads causes the meter needle
to dip and then climb again. |
The isolation capacitor is in series with the signal, most likely between the negative
terminal of the volume pot and the negative terminal of the jack. |
| Bridge & Middle |
Measure between the two terminals of the output (parallel DC resistance of
the bridge and middle pickups). |
Approximately equal to (bridge_resistance X
middle_resistance) divided by (bridge_resistance + middle_resistance). |
Normal. |
ditto |
ditto |
| Approximately the resistance of the bridge pickup. |
If the middle pickup passed its solo test above, this can only be a defective or
non-standard switch. |
ditto |
ditto |
| Approximately the resistance of the middle pickup. |
If the bridge pickup passed its solo test above, this can only be a defective or
non-standard switch. |
ditto |
ditto |
| Very high, but not open (approximately 250k to 500k). |
This would have to be a bad switch or else both pickups or wiring from
both pickups to switch would have to be bad. If both pickups passed their solo tests above then
this can only be a bad or nonstandard switch. |
ditto |
ditto |
| Open (greater than 2 Meg). |
Bad wiring between volume pot and jack, or bad volume pot. |
ditto |
ditto |
|
|
Meter reads very high (approximately 250k to 500k) (note, this
is most easily seen on a cheap analog meter). Reversing the meter leads causes the meter needle
to dip then climb again. |
The ground side of both pickups are attached to shield ground, instead of signal ground
(i.e. the wrong side of the isolation capacitor). |
|
|
Meter starts low, then climbs to open (greater than 2 Meg). (note, this
is most easily seen on a cheap analog meter). Reversing the meter leads causes the meter needle
to dip and then climb again. |
The isolation capacitor is in series with the signal, most likely between the negative
terminal of the volume pot and the negative terminal of the jack. |
|
If all of the above tests gave normal results you know that your pickups, switch, jack,
and internconnecting wiring are basically sound. (The switch may be "scratchy" but
it really takes a listening test (see Table I) to determine that.)
|
| Any position that checked "normal." |
Measure between the two terminals of the output while slowly turning down
the volume. |
Resistance climbs very rapidly at first then more slowly, until approximately half the
value of the volume pot is reached (usually at about 125k for a standard Strat with single coil pickups).
Then, resistance gradually decreases all the way to zero. |
Normal. |
ditto |
ditto |
| Resistance increases then decreases, but very evenly (i.e. the amount of change for a given
amount of pot rotation is approximately the same at all points |
Someone has installed a linear pot in the volume control, replace with an audio pot. |
ditto |
ditto |
| Resistance increases very slowly at first, then very rapidly. |
Someone has reversed the wires on the outside terminals of the volume pot. If the
volume control is still working in the correct direction then someone installed a reverse taper pot. |
ditto |
ditto |
| The needle on the meter jumps around a lot (this will only show on a very sensitive meter). |
The pot is dirty, worn, or of poor quality. (Note, in the listening test in Table
I this would have been heard as a scratching sound.) |
ditto |
ditto |
| Resistance doesn't go all the way to zero (or very, very near zero). |
The pot is worn, damaged, or of poor quality (it is not travelling fully to the
electrical end). |
ditto |
ditto |
| Neck |
Measure between the two terminals of the output while slowly turning down
the neck tone control. |
No change in reading. |
Normal. (Note, if during the listening test in Table I the tone control caused
the volume to decrease substantially, this result here being "normal" indicates that the tone capacitor
is of too large a value, as opposed to being shorted or wired incorrectly.) |
ditto |
ditto |
| Resistance decreases. |
The tone capacitor is shorted or the tone pot is wired incorrectly. |
ditto |
ditto |
| Middle |
Measure between the two terminals of the output while slowly turning down
the middle tone control. |
No change in reading. |
Normal. (Note, if during the listening test in Table I the tone control caused
the volume to decrease substantially, this result here being "normal" indicates that the tone capacitor
is of too large a value, as opposed to being shorted or wired incorrectly.) |
ditto |
ditto |
| Resistance decreases. |
The tone capacitor is shorted or the tone pot is wired incorrectly. |
ditto |
ditto |
| Any position that checked normal. |
Set the meter to its highest resistance scale and measure between the
negative terminal of the output and a metal part of the bridge. |
Zero resistance (short). |
Normal. |
ditto |
The isolation capacitor is bad or the signal return point is grounding
against the shielding. |
| Max resistance (open). |
The bridge ground wire is broken, disconnected, or missing; or the wires to the
output jack are reversed. |
ditto |
Reverse the meter leads. Each time you do so you should see the
resistance dip then return to an open - this is normal and indicates that the isolation capacitor is properly
wired. Note, some very inexpensive meters may not be sensitive enough to see the dip. If the
guitar passed the listening test (that is, hum got quieter instead of louder when you touched the strings)
then you can assume that the isolation capacitor is okay. If it failed that test the isolation
capacitor is open or not wired correctly.
|
| Any position that checked normal. |
Set the meter to its highest resistance scale and measure between the
positive terminal of the output and a metal part of the bridge. |
The same resistance as when measuring between the two output terminals. |
Normal. |
ditto |
The isolation capacitor is bad (shorted) or the signal return point is grounding
against the shielding, or the isolation capacitor is not wired properly. |
| Zero resistance (short). |
The wires to the output jack are reversed. |
ditto |
The wires to the output jack are reversed and the isolation capacitor is
bad (shorted), the signal return lead is shorting against the shielding, or the isolation capacitor is
not properly installed. |
|
