Lenovo 3000 N500 Owner's manual

Lenovo 3000 N500
Hardware Maintenance Manual

Lenovo 3000 N500
Hardware Maintenance Manual

Note
Before using this information and the product it supports, be sure to read the general information under “Notices” on page
113.
First Edition (October 2008)
©Copyright Lenovo 2008. All rights reserved.
LENOVO products, data, computer software, and services have been developed exclusively at private expense and
are sold to governmental entities as commercial items as defined by 48 C.F.R. 2.101 with limited and restricted
rights to use, reproduction and disclosure.
LIMITED AND RESTRICTED RIGHTS NOTICE: If products, data, computer software, or services are delivered
pursuant aGeneral Services Administration ″GSA″contract, use, reproduction, or disclosure is subject to restrictions
set forth in Contract No. GS-35F-05925.
©2008 Lenovo

Contents
About this manual ..........v
Safety information ..........1
General safety ..............2
Electrical safety .............3
Safety inspection guide ...........5
Handling devices that are sensitive to electrostatic
discharge ...............6
Grounding requirements ..........6
Safety notices: multilingual translations .....7
Laser compliance statement .........14
Important service information .....17
Strategy for replacing FRUs .........17
Strategy for replacing ahard disk drive ....18
Important notice for replacing asystem board ..18
How to use error message ........18
Strategy for replacing FRUs for CTO, CMV, and
GAV.................19
Product definition ...........19
FRU identification for CTO, CMV, and GAV
products ..............19
Important information about replacing RoHS
compliant FRUs .............21
General checkout ..........23
What to do first .............24
Checkout guide .............25
Diagnostics using PC-Doctor for DOS ....26
PC-Doctor for Windows .........28
Power system checkout ..........29
Checking the AC adapter .........29
Checking operational charging .......29
Checking the battery pack ........30
Related service information......31
Restoring the factory contents by using Product
Recovery discs .............31
Passwords ...............32
Power-on password ..........32
Hard-disk password ..........32
Supervisor password ..........33
How to remove the hard-disk password ....33
Power management ...........34
Screen blank mode ...........34
Sleep (standby) mode ..........34
Hibernation mode ...........35
Symptom-to-FRU index ..........36
Numeric error codes ..........36
Error messages ............38
Beep symptoms ............39
No-beep symptoms...........39
LCD-related symptoms .........40
Intermittent problems ..........41
Undetermined problems .........41
Lenovo 3000 N500 ..........43
Specifications ..............43
Status indicators .............45
FRU tests ...............47
Fn key combinations ...........48
FRU replacement notices ..........49
Screw notices .............49
Retaining serial numbers .........50
Removing and replacing aFRU........53
1010 Battery pack ...........54
1020 Dummy cards ...........55
1030 Hard disk drive (HDD) slot cover and HDD 56
1040 Optical drive ...........58
1050 Thermal slot cover .........59
1060 DIMM .............60
1070 Fan assembly ...........61
1080 Heat sink assembly .........63
1090 Wireless LAN card slot cover and PCI
Express Mini Card for wireless LAN .....65
1100 CPU ..............67
1110 Keyboard cover and power board ....68
1120 Bluetooth daughter card (BDC-2.1) ....70
1130 Keyboard ............71
1140 LCD unit ............73
1150 Keyboard bezel and LED board L....76
1160 LED board R...........79
1170 System board and ExpressCard slot
assembly ..............80
1180 Speakers and base cover .......84
2010 LCD front bezel ..........86
2020 Inverter card ...........87
2030 Integrated camera .........88
2040 LCD panel, LCD cable, and hinges ....89
2050 Antenna assembly and LCD cover ....92
Locations ...............93
Front view..............93
Rear view ..............95
Bottom view .............95
Parts list ...............96
Overall ...............97
LCD FRUs ............. 101
Keyboard.............. 103
Miscellaneous parts .......... 104
AC adapters............. 105
Power cords ............. 106
Recovery discs ............ 107
Common service tools ......... 111
Notices ..............113
Trademarks ..............114
©Copyright Lenovo 2008 iii

iv Lenovo 3000 N500 Hardware Maintenance Manual

About this manual
This manual contains service and reference information for the following Lenovo
3000 products.
Lenovo 3000 N500
MT 4233
Use this manual along with the advanced diagnostic tests to troubleshoot
problems.
The manual is divided into sections as follows:
vThe common sections provide general information, guidelines, and safety
information required in servicing computers.
vThe product-specific section includes service, reference, and product-specific
parts information.
Important:
This manual is intended only for trained servicers who are familiar with Lenovo
3000 products. Use this manual along with the advanced diagnostic tests to
troubleshoot problems effectively.
Before servicing aLenovo 3000 product, be sure to read all the information
under “Safety information” on page 1and “Important service information” on
page 17.
©Copyright Lenovo 2008 v

vi Lenovo 3000 N500 Hardware Maintenance Manual

Safety information
This chapter presents following safety information that you need to be familiar
with before you service aLenovo 3000 computer.
v“General safety” on page 2
v“Electrical safety” on page 3
v“Safety inspection guide” on page 5
v“Handling devices that are sensitive to electrostatic discharge” on page 6
v“Grounding requirements” on page 6
v“Safety notices: multilingual translations” on page 7
v“Laser compliance statement” on page 14
©Copyright Lenovo 2008 1

General safety
Follow these rules to ensure general safety:
vObserve good housekeeping in the area of the machines during and after
maintenance.
vWhen lifting any heavy object:
1. Make sure that you can stand safely without slipping.
2. Distribute the weight of the object equally between your feet.
3. Use aslow lifting force. Never move suddenly or twist when you attempt to
lift.
4. Lift by standing or by pushing up with your leg muscles; this action removes
the strain from the muscles in your back. Do not attempt to lift any object that
weighs more than 16 kg (35 lb) or that you think is too heavy for you.
vDo not perform any action that causes hazards to the customer, or that makes
the equipment unsafe.
vBefore you start the machine, make sure that other service representatives and
the customer’s personnel are not in ahazardous position.
vPlace removed covers and other parts in asafe place, away from all personnel,
while you are servicing the machine.
vKeep your toolcase away from walk areas so that other people will not trip over
it.
vDo not wear loose clothing that can be trapped in the moving parts of a
machine. Make sure that your sleeves are fastened or rolled up above your
elbows. If your hair is long, fasten it.
vInsert the ends of your necktie or scarf inside clothing or fasten it with a
nonconductive clip, about 8centimeters (3 inches) from the end.
vDo not wear jewelry, chains, metal-frame eyeglasses, or metal fasteners for your
clothing.
Attention: Metal objects are good electrical conductors.
vWear safety glasses when you are hammering, drilling, soldering, cutting wire,
attaching springs, using solvents, or working in any other conditions that might
be hazardous to your eyes.
vAfter service, reinstall all safety shields, guards, labels, and ground wires.
Replace any safety device that is worn or defective.
vReinstall all covers correctly before returning the machine to the customer.
vFan louvers on the machine help to prevent overheating of internal components.
Do not obstruct fan louvers or cover them with labels or stickers.
2Lenovo 3000 N500 Hardware Maintenance Manual

Electrical safety
Observe the following rules when working on electrical equipment.
vFind the room emergency power-off (EPO) switch, disconnecting switch, or
electrical outlet. If an electrical accident occurs, you can then operate the switch
or unplug the power cord quickly.
vDo not work alone under hazardous conditions or near equipment that has
hazardous voltages.
vDisconnect all power before:
–Performing amechanical inspection
–Working near power supplies
–Removing or installing main units
vBefore you start to work on the machine, unplug the power cord. If you cannot
unplug it, ask the customer to power-off the wall box that supplies power to the
machine, and to lock the wall box in the off position.
vIf you need to work on amachine that has exposed electrical circuits, observe the
following precautions:
–Ensure that another person, familiar with the power-off controls, is near you.
Attention: Another person must be there to switch off the power, if
necessary.
–Use only one hand when working with powered-on electrical equipment;
keep the other hand in your pocket or behind your back.
Attention: An electrical shock can occur only when there is acomplete
circuit. By observing the above rule, you may prevent acurrent from passing
through your body.
–When using testers, set the controls correctly and use the approved probe
leads and accessories for that tester.
–Stand on suitable rubber mats (obtained locally, if necessary) to insulate you
from grounds such as metal floor strips and machine frames.
Observe the special safety precautions when you work with very high voltages;
Instructions for these precautions are in the safety sections of maintenance
information. Use extreme care when measuring high voltages.
vRegularly inspect and maintain your electrical hand tools for safe operational
condition.
vDo not use worn or broken tools and testers.
vNever assume that power has been disconnected from acircuit. First, check that it
has been powered off.
vAlways look carefully for possible hazards in your work area. Examples of these
hazards are moist floors, nongrounded power extension cables, power surges,
and missing safety grounds.
Important:
Use only approved tools and test equipment. Some hand tools have handles
covered with asoft material that does not insulate you when working with live
electrical currents.
Many customers have, near their equipment, rubber floor mats that contain small
conductive fibers to decrease electrostatic discharges. Do not use this type of mat
to protect yourself from electrical shock.
Safety information 3

vDo not touch live electrical circuits with the reflective surface of aplastic dental
mirror. The surface is conductive; such touching can cause personal injury and
machine damage.
vDo not service the following parts with the power on when they are removed
from their normal operating places in amachine:
–Power supply units
–Pumps
–Blowers and fans
–Motor generators
and similar units. (This practice ensures correct grounding of the units.)
vIf an electrical accident occurs:
–Use caution; do not become avictim yourself.
–Switch off power.
–Send another person to get medical aid.
4Lenovo 3000 N500 Hardware Maintenance Manual

Safety inspection guide
The purpose of this inspection guide is to assist you in identifying potentially
unsafe conditions. As each machine was designed and built, required safety items
were installed to protect users and service personnel from injury. This guide
addresses only those items. You should use good judgment to identify potential
safety hazards due to attachment of non-Lenovo 3000 features or options not
covered by this inspection guide.
If any unsafe conditions are present, you must determine how serious the apparent
hazard could be and whether you can continue without first correcting the
problem.
Consider these conditions and the safety hazards they present:
vElectrical hazards, especially primary power (primary voltage on the frame can
cause serious or fatal electrical shock)
vExplosive hazards, such as adamaged CRT face or abulging capacitor
vMechanical hazards, such as loose or missing hardware
To determine whether there are any potentially unsafe conditions, use the
following checklist at the beginning of every service task. Begin the checks with
the power off, and the power cord disconnected.
Checklist:
1. Check exterior covers for damage (loose, broken, or sharp edges).
2. Power off the computer. Disconnect the power cord.
3. Check the power cord for:
a. Athird-wire ground connector in good condition. Use ameter to measure
third-wire ground continuity for 0.1 ohm or less between the external
ground pin and the frame ground.
b. The power cord should be the type specified in the parts list.
c. Insulation must not be frayed or worn.
4. Check for cracked or bulging batteries.
5. Remove the cover.
6. Check for any obvious non-Lenovo 3000 alterations. Use good judgment as to
the safety of any non-Lenovo 3000 alterations.
7. Check inside the unit for any obvious unsafe conditions, such as metal filings,
contamination, water or other liquids, or signs of fire or smoke damage.
8. Check for worn, frayed, or pinched cables.
9. Check that the power-supply cover fasteners (screws or rivets) have not been
removed or tampered with.
Safety information 5

Handling devices that are sensitive to electrostatic discharge
Any computer part containing transistors or integrated circuits (ICs) should be
considered sensitive to electrostatic discharge (ESD.) ESD damage can occur when
there is adifference in charge between objects. Protect against ESD damage by
equalizing the charge so that the machine, the part, the work mat, and the person
handling the part are all at the same charge.
When handling ESD-sensitive parts:
vKeep the parts in protective packages until they are inserted into the product.
vAvoid contact with other people.
vWear agrounded wrist strap against your skin to eliminate static on your body.
vPrevent the part from touching your clothing. Most clothing is insulative and
retains acharge even when you are wearing awrist strap.
vUse the black side of agrounded work mat to provide astatic-free work surface.
The mat is especially useful when handling ESD-sensitive devices.
vSelect agrounding system, such as those listed below, to provide protection that
meets the specific service requirement.
–Attach the ESD ground clip to any frame ground, ground braid, or green-wire
ground.
–When working on adouble-insulated or battery-operated system, use an ESD
common ground or reference point. You can use coax or connector-outside
shells on these systems.
–Use the round ground prong of the ac plug on ac-operated computers.
Grounding requirements
Electrical grounding of the computer is required for operator safety and correct
system function. Proper grounding of the electrical outlet can be verified by a
certified electrician.
Notes:
1. Use product-specific ESD procedures when they exceed the requirements
noted here.
2. Make sure that the ESD protective devices you use have been certified (ISO
9000) as fully effective.
Note:
The use of agrounding system to guard against ESD damage is desirable but not
necessary.
6Lenovo 3000 N500 Hardware Maintenance Manual

Safety notices: multilingual translations
The safety notices in this section are provided in English, French, German, Hebrew,
Italian, Japanese, and Spanish.
Safety notice 1
Before the computer is powered on after FRU replacement, make sure all screws,
springs, and other small parts are in place and are not left loose inside the
computer. Verify this by shaking the computer and listening for rattling sounds.
Metallic parts or metal flakes can cause electrical shorts.
Avant de remettre l’ordinateur sous tension après remplacement d’une unité en
clientèle, vérifiez que tous les ressorts, vis et autres pièces sont bien en place et
bien fixées. Pour ce faire, secouez l’unité et assurez-vous qu’aucun bruit suspect
ne se produit. Des pièces métalliques ou des copeaux de métal pourraient causer
un court-circuit.
Bevor nach einem FRU-Austausch der Computer wieder angeschlossen wird,
muß sichergestellt werden, daß keine Schrauben, Federn oder andere Kleinteile
fehlen oder im Gehäuse vergessen wurden. Der Computer muß geschüttelt und
auf Klappergeräusche geprüft werden. Metallteile oder-splitter können
Kurzschlüsse erzeugen.
Prima di accendere l’elaboratore dopo che éstata effettuata la sostituzione di una FRU,
accertarsi che tutte le viti, le molle etutte le altri parti di piccole dimensioni siano nella
corretta posizione enon siano sparse all’interno dell’elaboratore. Verificare ciò scuotendo
l’elaboratore eprestando attenzione ad eventuali rumori; eventuali parti opezzetti
metallici possono provocare cortocircuiti pericolosi.
Antes de encender el sistema despues de sustituir una FRU, compruebe que todos los
tornillos, muelles ydemás piezas pequeñas se encuentran en su sitio yno se encuentran
sueltas dentro del sistema. Compruébelo agitando el sistema yescuchando los posibles
ruidos que provocarían. Las piezas metálicas pueden causar cortocircuitos eléctricos.
Safety information 7

Safety notice 2
DANGER
Some standby batteries contain asmall amount of nickel and cadmium. Do not
disassemble astandby battery, recharge it, throw it into fire or water, or short-circuit it.
Dispose of the battery as required by local ordinances or regulations. Use only the
battery in the appropriate parts listing. Use of an incorrect battery can result in
ignition or explosion of the battery.
Certaines batteries de secours contiennent du nickel et du cadmium. Ne les démontez
pas, ne les rechargez pas, ne les exposez ni au feu ni àl’eau. Ne les mettez pas en
court-circuit. Pour les mettre au rebut, conformez-vous àla réglementation en vigueur.
Lorsque vous remplacez la pile de sauvegarde ou celle de l’horloge temps réel, veillez
àn’utiliser que les modèles cités dans la liste de pièces détachées adéquate. Une
batterie ou une pile inappropriée risque de prendre feu ou d’exploser.
Die Bereitschaftsbatterie, die sich unter dem Diskettenlaufwerk befindet, kann
geringe Mengen Nickel und Cadmium enthalten. Sie darf nur durch die Verkaufsstelle
oder den IBM Kundendienst ausgetauscht werden. Sie darf nicht zerlegt,
wiederaufgeladen, kurzgeschlossen, oder Feuer oder Wasser ausgesetzt werden. Die
Batterie kann schwere Verbrennungen oder Verätzungen verursachen. Bei der
Entsorgung die örtlichen Bestimmungen für Sondermüll beachten. Beim Ersetzen der
Bereitschafts-oder Systembatterie nur Batterien des Typs verwenden, der in der
Ersatzteilliste aufgeführt ist. Der Einsatz falscher Batterien kann zu Entzündung oder
Explosion führen.
Alcune batterie di riserva contengono una piccola quantità di nichel ecadmio. Non
smontarle, ricaricarle, gettarle nel fuoco onell’acqua né cortocircuitarle. Smaltirle
secondo la normativa in vigore (DPR 915/82, successive disposizioni edisposizioni
locali). Quando si sostituisce la batteria dell’RTC (real time clock) ola batteria di
supporto, utilizzare soltanto itipi inseriti nell’appropriato Catalogo parti. L’impiego di
una batteria non adatta potrebbe determinare l’incendio ol’esplosione della batteria
stessa.
Algunas baterías de reserva contienen una pequeña cantidad de níquel ycadmio. No
las desmonte, ni recargue, ni las eche al fuego oal agua ni las cortocircuite.
Deséchelas tal como dispone la normativa local. Utilice sólo baterías que se
encuentren en la lista de piezas. La utilización de una batería no apropiada puede
provocar la ignición oexplosión de la misma.
8Lenovo 3000 N500 Hardware Maintenance Manual

Safety notice 3
DANGER
The battery pack contains small amounts of nickel. Do not disassemble it, throw it
into fire or water, or short-circuit it. Dispose of the battery pack as required by local
ordinances or regulations. Use only the battery in the appropriate parts listing when
replacing the battery pack. Use of an incorrect battery can result in ignition or
explosion of the battery.
La batterie contient du nickel. Ne la démontez pas, ne l’exposez ni au feu ni àl’eau.
Ne la mettez pas en court-circuit. Pour la mettre au rebut, conformez-vous àla
réglementation en vigueur. Lorsque vous remplacez la batterie, veillez àn’utiliser que
les modèles cités dans la liste de pièces détachées adéquate. En effet, une batterie
inappropriée risque de prendre feu ou d’exploser.
Akkus enthalten geringe Mengen von Nickel. Sie dürfen nicht zerlegt,
wiederaufgeladen, kurzgeschlossen, oder Feuer oder Wasser ausgesetzt werden. Bei
der Entsorgung die örtlichen Bestimmungen für Sondermüll beachten. Beim Ersetzen
der Batterie nur Batterien des Typs verwenden, der in der Ersatzteilliste aufgeführt ist.
Der Einsatz falscher Batterien kann zu Entzündung oder Explosion führen.
La batteria contiene piccole quantità di nichel. Non smontarla, gettarla nel fuoco o
nell’acqua né cortocircuitarla. Smaltirla secondo la normativa in vigore (DPR 915/82,
successive disposizioni edisposizioni locali). Quando si sostituisce la batteria,
utilizzare soltanto itipi inseriti nell’appropriato Catalogo parti. L’impiego di una
batteria non adatta potrebbe determinare l’incendio ol’esplosione della batteria stessa.
Las baterías contienen pequeñas cantidades de níquel. No las desmonte, ni recargue,
ni las eche al fuego oal agua ni las cortocircuite. Deséchelas tal como dispone la
normativa local. Utilice sólo baterías que se encuentren en la lista de piezas al
sustituir la batería. La utilización de una batería no apropiada puede provocar la
ignición oexplosión de la misma.
Safety information 9

Safety notice 4
DANGER
The lithium battery can cause afire, an explosion, or asevere burn. Do not recharge it,
remove its polarized connector, disassemble it, heat it above 100°C (212°F), incinerate
it, or expose its cell contents to water. Dispose of the battery as required by local
ordinances or regulations. Use only the battery in the appropriate parts listing. Use of
an incorrect battery can result in ignition or explosion of the battery.
La pile de sauvegarde contient du lithium. Elle présente des risques d’incendie,
d’explosion ou de brûlures graves. Ne la rechargez pas, ne retirez pas son connecteur
polarisé et ne la démontez pas. Ne l’exposez pas àune temperature supérieure à100°C,
ne la faites pas brûler et n’en exposez pas le contenu àl’eau. Mettez la pile au rebut
conformément àla réglementation en vigueur. Une pile inappropriée risque de
prendre feu ou d’exploser.
Die Systembatterie ist eine Lithiumbatterie. Sie kann sich entzünden, explodieren
oder schwere Verbrennungen hervorrufen. Batterien dieses Typs dürfen nicht
aufgeladen, zerlegt, über 100 Cerhitzt oder verbrannt werden. Auch darf ihr Inhalt
nicht mit Wasser in Verbindung gebracht oder der zur richtigen Polung angebrachte
Verbindungsstecker entfernt werden. Bei der Entsorgung die örtlichen Bestimmungen
für Sondermüll beachten. Beim Ersetzen der Batterie nur Batterien des Typs
verwenden, der in der Ersatzteilliste aufgeführt ist. Der Einsatz falscher Batterien
kann zu Entzündung oder Explosion führen.
La batteria di supporto euna batteria al litio epuo incendiarsi, esplodere oprocurare
gravi ustioni. Evitare di ricaricarla, smontarne il connettore polarizzato, smontarla,
riscaldarla ad una temperatura superiore ai 100 gradi centigradi, incendiarla ogettarla
in acqua. Smaltirla secondo la normativa in vigore (DPR 915/82, successive
disposizioni edisposizioni locali). L’impiego di una batteria non adatta potrebbe
determinare l’incendio ol’esplosione della batteria stessa.
La batería de repuesto es una batería de litio ypuede provocar incendios, explosiones
oquemaduras graves. No la recargue, ni quite el conector polarizado, ni la desmonte,
ni caliente por encima de los 100°C (212°F), ni la incinere ni exponga el contenido de
sus celdas al agua. Deséchela tal como dispone la normativa local.
10 Lenovo 3000 N500 Hardware Maintenance Manual

Safety notice 5
If the LCD breaks and the fluid from inside the LCD gets into your eyes or on
your hands, immediately wash the affected areas with water for at least 15
minutes. Seek medical care if any symptoms from the fluid are present after
washing.
Si le panneau d’affichage àcristaux liquides se brise et que vous recevez dans les
yeux ou sur les mains une partie du fluide, rincez-les abondamment pendant au
moins quinze minutes. Consultez un médecin si des symptômes persistent après
le lavage.
Die Leuchtstoffröhre im LCD-Bildschirm enthält Quecksilber. Bei der Entsorgung
die örtlichen Bestimmungen für Sondermüll beachten. Der LCD-Bildschirm
besteht aus Glas und kann zerbrechen, wenn er unsachgemäß behandelt wird
oder der Computer auf den Boden fällt. Wenn der Bildschirm beschädigt ist und
die darin befindliche Flüssigkeit in Kontakt mit Haut und Augen gerät, sollten
die betroffenen Stellen mindestens 15 Minuten mit Wasser abgespült und bei
Beschwerden anschließend ein Arzt aufgesucht werden.
Nel caso che caso l’LCD si dovesse rompere ed il liquido in esso contenuto entrasse in
contatto con gli occhi ole mani, lavare immediatamente le parti interessate con acqua
corrente per almeno 15 minuti; poi consultare un medico se isintomi dovessero
permanere.
Si la LCD se rompe yel fluido de su interior entra en contacto con sus ojos osus manos,
lave inmediatamente las áreas afectadas con agua durante 15 minutos como mínimo.
Obtenga atención medica si se presenta algún síntoma del fluido despues de lavarse.
Safety information 11

Safety notice 6
DANGER
To avoid shock, do not remove the plastic cover that protects the lower part of the
inverter card.
Afin d’éviter tout risque de choc électrique, ne retirez pas le cache en plastique
protégeant la partie inférieure de la carte d’alimentation.
Aus Sicherheitsgründen die Kunststoffabdeckung, die den unteren Teil der
Spannungswandlerplatine umgibt, nicht entfernen.
Per evitare scosse elettriche, non rimuovere la copertura in plastica che avvolge la
parte inferiore della scheda invertitore.
Para evitar descargas, no quite la cubierta de plástico que rodea la parte baja de la
tarjeta invertida.
Safety notice 7
DANGER
Though the main batteries have low voltage, ashorted or grounded battery can
produce enough current to burn personnel or combustible materials.
Bien que le voltage des batteries principales soit peu élevé, le court-circuit ou la mise
àla masse d’une batterie peut produire suffisamment de courant pour brûler des
matériaux combustibles ou causer des brûlures corporelles graves.
Obwohl Hauptbatterien eine niedrige Spannung haben, können sie doch bei
Kurzschluß oder Erdung genug Strom abgeben, um brennbare Materialien zu
entzünden oder Verletzungen bei Personen hervorzurufen.
Sebbene le batterie di alimentazione siano abasso voltaggio, una batteria in corto
circuito oamassa può fornire corrente sufficiente da bruciare materiali combustibili o
provocare ustioni ai tecnici di manutenzione.
Aunque las baterías principales tienen un voltaje bajo, una batería cortocircuitada o
con contacto atierra puede producir la corriente suficiente como para quemar material
combustible oprovocar quemaduras en el personal.
12 Lenovo 3000 N500 Hardware Maintenance Manual