Lenovo 11KC000XGE Owner's manual

M75t Gen 2
Hardware Maintenance Manual

Second Edition (June 2021)
© Copyright Lenovo 2021.
LIMITED AND RESTRICTED RIGHTS NOTICE: If data r s ftware is delivered pursuant t a General Services
Administrati n “GSA” c ntract, use, repr ducti n, r discl sure is subject t restricti ns set f rth in C ntract N . GS-
35F-05925.

Contents
About this m nu l . . . . . . . . . . . . iii
Ch pter 1. Import nt s fety
inform tion. . . . . . . . . . . . . . . . 1
General safety . . . . . . . . . . . . . . . . 1
Electrical safety . . . . . . . . . . . . . . . . 2
Safety inspecti n guide. . . . . . . . . . . . . 3
Handling electr static discharge-sensitive
devices . . . . . . . . . . . . . . . . . . . 4
Gr unding requirements . . . . . . . . . . . . 4
Safety n tices (multi-lingual translati ns) . . . . . . 4
Ch pter 2. Import nt service
inform tion. . . . . . . . . . . . . . . 27
Strategy f r replacing FRUs . . . . . . . . . . 27
Strategy f r replacing a hard disk drive r a
s lid-state drive . . . . . . . . . . . . . 27
Imp rtant n tice f r replacing a system
b ard . . . . . . . . . . . . . . . . . 27
H w t use err r c des . . . . . . . . . . 28
Strategy f r replacing FRUs f r CTO, special-bid,
and standard m dels. . . . . . . . . . . . . 28
Pr duct definiti n . . . . . . . . . . . . 28
FRU identificati n . . . . . . . . . . . . 28
Ch pter 3. Product overview . . . . . 29
Fr nt . . . . . . . . . . . . . . . . . . . 29
Rear . . . . . . . . . . . . . . . . . . . 30
Ch pter 4. Service checkout nd
symptom-to-FRU index . . . . . . . . 31
Service check ut . . . . . . . . . . . . . . 31
Pr blem determinati n tips . . . . . . . . 31
Sympt m-t -FRU index . . . . . . . . . . . 32
Hard disk drive b t err r . . . . . . . . . 32
P wer supply pr blems . . . . . . . . . . 33
Beep sympt ms . . . . . . . . . . . . . 33
POST err r c des . . . . . . . . . . . . 34
Miscellane us err r c nditi ns . . . . . . . 34
Undetermined pr blems . . . . . . . . . 36
Ch pter 5. Troubleshooting,
di gnostics, nd recovery . . . . . . . 39
Basic pr cedure f r res lving c mputer
pr blems . . . . . . . . . . . . . . . . . 39
Tr ublesh ting . . . . . . . . . . . . . . 39
Startup pr blems . . . . . . . . . . . . 40
Audi pr blems . . . . . . . . . . . . . 41
Netw rk pr blems . . . . . . . . . . . . 41
Perf rmance pr blems . . . . . . . . . . 44
St rage drive pr blems . . . . . . . . . . 45
CD r DVD pr blems . . . . . . . . . . . 45
Serial c nnect r pr blems . . . . . . . . . 46
USB device pr blems . . . . . . . . . . 46
S ftware pr blems. . . . . . . . . . . . 47
Diagn stics . . . . . . . . . . . . . . . . 47
Len v diagn stic t ls . . . . . . . . . . 47
UEFI diagn stic pr gram . . . . . . . . . 47
Rec very . . . . . . . . . . . . . . . . . 48
Rest re system files and settings t an earlier
p int . . . . . . . . . . . . . . . . . 48
Rest re y ur files fr m a backup . . . . . . 48
Reset y ur c mputer . . . . . . . . . . . 48
Use advanced pti ns . . . . . . . . . . 48
Wind ws aut matic rec very. . . . . . . . 49
Create and use a rec very USB device . . . . 49
Update the device driver . . . . . . . . . 49
Ch pter 6. H rdw re remov l nd
inst ll tion . . . . . . . . . . . . . . . 51
Handling static-sensitive devices . . . . . . . . 51
Service t l kit . . . . . . . . . . . . . . . 51
Maj r FRUs and CRUs . . . . . . . . . . . . 52
System b ard . . . . . . . . . . . . . . . 56
Rem ving and installing hardware . . . . . . . 57
External pti ns . . . . . . . . . . . . . 57
C mputer c ver . . . . . . . . . . . . . 57
Fr nt bezel . . . . . . . . . . . . . . . 57
Optical drive . . . . . . . . . . . . . . 58
Drive bay assembly . . . . . . . . . . . 59
Hard disk drive . . . . . . . . . . . . . 60
M.2 s lid-state drive and heat sink . . . . . 62
M.2 s lid-state drive bracket . . . . . . . . 64
Mem ry m dule . . . . . . . . . . . . . 65
PCI-Express card . . . . . . . . . . . . 66
C in-cell battery. . . . . . . . . . . . . 67
E-l ck . . . . . . . . . . . . . . . . . 68
P wer supply assembly . . . . . . . . . . 69
Wi-Fi Card . . . . . . . . . . . . . . . 70
Card reader . . . . . . . . . . . . . . 70
Fr nt I/O bracket . . . . . . . . . . . . 71
Thermal sens r . . . . . . . . . . . . . 73
Fr nt fan. . . . . . . . . . . . . . . . 74
Rear fan . . . . . . . . . . . . . . . . 74
Wi-Fi antenna and cable. . . . . . . . . . 75
C ver presence switch . . . . . . . . . . 77
© C pyright Len v 2021 i

Heat sink and fan assembly . . . . . . . . 78
Micr pr cess r . . . . . . . . . . . . . 79
System b ard. . . . . . . . . . . . . . 80
Ch pter 7. Notices nd
tr dem rks. . . . . . . . . . . . . . . 83
ii M75t Gen 2 Hardware Maintenance Manual

About this m nu l
This manual pr vides service and reference inf rmati n f r ThinkCentre® c mputers listed n the fr nt c ver.
Illustrati ns in this manual might l k different fr m y ur pr duct.
Use this manual al ng with the advanced diagn stic tests t tr ublesh t pr blems.
Import nt: This manual is intended nly f r trained service technicians wh are familiar with ThinkCentre
c mputers. Use this manual al ng with the advanced diagn stic tests t tr ublesh t pr blems effectively.
Bef re servicing a ThinkCentre c mputer, be sure t read and understand Chapter 1 “Imp rtant safety
inf rmati n” n page 1.
© C pyright Len v 2021 iii

iv M75t Gen 2 Hardware Maintenance Manual

Ch pter 1. Import nt s fety inform tion
Gener l s fety
F ll w these rules t ensure general safety:
• Observe g d h usekeeping in the area f the machines during and after maintenance.
• When lifting any heavy bject:
1. Ensure y u can stand safely with ut slipping.
2. Distribute the weight f the bject equally between y ur feet.
3. Use a sl w lifting f rce. Never m ve suddenly r twist when y u attempt t lift.
4. Lift by standing r by pushing up with y ur leg muscles; this acti n rem ves the strain fr m the
muscles in y ur back.
Attention: D n t attempt t lift any bjects that weigh m re than 16 kg (35 lb) r bjects that y u
think are t heavy f r y u.
• D n t perf rm any acti n that causes hazards t the cust mer, r that makes the equipment unsafe.
• Bef re y u start the machine, ensure that ther service representatives and the cust mer's pers nnel are
n t in a hazard us p siti n.
• Place rem ved c vers and ther parts in a safe place, away fr m all pers nnel, while y u are servicing the
machine.
• Keep y ur t l case away fr m walk areas s that ther pe ple will n t trip ver it.
• D n t wear l se cl thing that can be trapped in the m ving parts f a machine. Ensure that y ur sleeves
are fastened r r lled up ab ve y ur elb ws. If y ur hair is l ng, fasten it.
• Insert the ends f y ur necktie r scarf inside cl thing r fasten it with a n nc nductive clip, appr ximately
8 centimeters (3 inches) fr m the end.
• D n t wear jewelry, chains, metal-frame eyeglasses, r metal fasteners f r y ur cl thing.
Remember: Metal bjects are g d electrical c nduct rs.
• Wear safety glasses when y u are: hammering, drilling, s ldering, cutting wire, attaching springs, using
s lvents, r w rking in any ther c nditi ns that might be hazard us t y ur eyes.
• After service, reinstall all safety shields, guards, labels, and gr und wires. Replace any safety device that
is w rn r defective.
• Reinstall all c vers c rrectly bef re returning the machine t the cust mer.
CAUTION:
Keep fingers nd other p rts of your body w y from h z rdous, moving p rts. If you suffer n injury,
seek medic l c re immedi tely.
CAUTION:
Avoid cont ct with hot components inside the computer. During oper tion, some components
become hot enough to burn the skin. Before you open the computer cover, turn off the computer,
disconnect power, nd w it pproxim tely 10 minutes for the components to cool.
© C pyright Len v 2021 1

Electric l s fety
CAUTION:
Electric l current from power, telephone, nd communic tion c bles c n be h z rdous. To void
person l injury or equipment d m ge, disconnect the tt ched power cords, telecommunic tion
systems, networks, nd modems before you open the computer covers, unless instructed otherwise
in the inst ll tion nd configur tion procedures.
Observe the f ll wing rules when w rking n electrical equipment.
Import nt: Use nly appr ved t ls and test equipment. S me hand t ls have handles c vered with a s ft
material that d es n t insulate y u when w rking with live electrical currents. Many cust mers have, near
their equipment, rubber fl r mats that c ntain small c nductive fibers t decrease electr static discharges.
D n t use this type f mat t pr tect y urself fr m electrical sh ck.
• Find the r m emergency p wer- ff (EPO) switch, disc nnecting switch, r electrical utlet. If an electrical
accident ccurs, y u can then perate the switch r unplug the p wer c rd quickly.
• D n t w rk al ne under hazard us c nditi ns r near equipment that has hazard us v ltages.
• Disc nnect all p wer bef re:
– Perf rming a mechanical inspecti n
– W rking near p wer supplies
– Rem ving r installing Field Replaceable Units (FRUs)
• Bef re y u start t w rk n the machine, unplug the p wer c rd. If y u cann t unplug it, ask the cust mer
t p wer- ff the wall b x that supplies p wer t the machine and t l ck the wall b x in the ff p siti n.
• If y u need t w rk n a machine that has exp sed electrical circuits, bserve the f ll wing precauti ns:
– Ensure that an ther pers n, familiar with the p wer- ff c ntr ls, is near y u.
Remember: An ther pers n must be there t switch ff the p wer, if necessary.
– Use nly ne hand when w rking with p wered- n electrical equipment; keep the ther hand in y ur
p cket r behind y ur back.
Remember: There must be a c mplete circuit t cause electrical sh ck. By bserving the ab ve rule,
y u may prevent a current fr m passing thr ugh y ur b dy.
– When using a tester, set the c ntr ls c rrectly and use the appr ved pr be leads and access ries f r
that tester.
– Stand n suitable rubber mats ( btained l cally, if necessary) t insulate y u fr m gr unds such as
metal fl r strips and machine frames.
Observe the special safety precauti ns when y u w rk with very high v ltages; these instructi ns are in
the safety secti ns f maintenance inf rmati n. Use extreme care when measuring high v ltages.
• Regularly inspect and maintain y ur electrical hand t ls f r safe perati nal c nditi n.
• D n t use w rn r br ken t ls and testers.
• Never assume that p wer has been disc nnected fr m a circuit. First, check that it has been p wered- ff.
• Always l k carefully f r p ssible hazards in y ur w rk area. Examples f these hazards are m ist fl rs,
n ngr unded p wer extensi n cables, p wer surges, and missing safety gr unds.
• D n t t uch live electrical circuits with the reflective surface f a plastic dental mirr r. The surface is
c nductive; such t uching can cause pers nal injury and machine damage.
2M75t Gen 2 Hardware Maintenance Manual

• D n t service the f ll wing parts with the p wer n when they are rem ved fr m their n rmal perating
places in a machine:
– P wer supply units
– Pumps
– Bl wers and fans
– M t r generat rs
and similar units. (This practice ensures c rrect gr unding f the units.)
• If an electrical accident ccurs:
– Use cauti n; d n t bec me a victim y urself.
– Switch ff p wer.
– Send an ther pers n t get medical aid.
S fety inspection guide
The intent f this inspecti n guide is t assist y u in identifying p tentially unsafe c nditi ns n these
pr ducts. Each machine, as it was designed and built, had required safety items installed t pr tect users
and service pers nnel fr m injury. This guide addresses nly th se items. H wever, g d judgment sh uld
be used t identify p tential safety hazards due t attachment f features r pti ns n t c vered by this
inspecti n guide.
If any unsafe c nditi ns are present, y u must determine h w seri us the apparent hazard c uld be and
whether y u can c ntinue with ut first c rrecting the pr blem.
C nsider these c nditi ns and the safety hazards they present:
• Electrical hazards, especially primary p wer (primary v ltage n the frame can cause seri us r fatal
electrical sh ck).
• Expl sive hazards, such as a damaged CRT face r bulging capacit r
• Mechanical hazards, such as l se r missing hardware
The guide c nsists f a series f steps presented in a checklist. Begin the checks with the p wer ff, and the
p wer c rd disc nnected.
Checklist:
1. Check exteri r c vers f r damage (l se, br ken, r sharp edges).
2. P wer- ff the c mputer. Disc nnect the p wer c rd.
3. Check the p wer c rd f r:
a. A third-wire gr und c nnect r in g d c nditi n. Use a meter t measure third-wire gr und
c ntinuity f r 0.1 hm r less between the external gr und pin and frame gr und.
b. The p wer c rd sh uld be the appr priate type as specified in the parts listings.
c. Insulati n must n t be frayed r w rn.
4. Rem ve the c ver.
5. Check f r any bvi us alterati ns. Use g d judgment as t the safety f any alterati ns.
6. Check inside the unit f r any bvi us unsafe c nditi ns, such as metal filings, c ntaminati n, water r
ther liquids, r signs f fire r sm ke damage.
7. Check f r w rn, frayed, r pinched cables.
Chapter 1.Imp rtant safety inf rmati n 3

8. Check that the p wer-supply c ver fasteners (screws r rivets) have n t been rem ved r tampered
with.
H ndling electrost tic disch rge-sensitive devices
Any c mputer part c ntaining transist rs r integrated circuits (ICs) sh uld be c nsidered sensitive t
electr static discharge (ESD). ESD damage can ccur when there is a difference in charge between bjects.
Pr tect against ESD damage by equalizing the charge s that the machine, the part, the w rk mat, and the
pers n handling the part are all at the same charge.
Notes:
1. Use pr duct-specific ESD pr cedures when they exceed the requirements n ted here.
2. Make sure that the ESD pr tective devices y u use have been certified (ISO 9000) as fully effective.
When handling ESD-sensitive parts:
• Keep the parts in pr tective packages until they are inserted int the pr duct.
• Av id c ntact with ther pe ple while handling the part.
• Wear a gr unded wrist strap against y ur skin t eliminate static n y ur b dy.
• Prevent the part fr m t uching y ur cl thing. M st cl thing is insulative and retains a charge even when
y u are wearing a wrist strap.
• Use the black side f a gr unded w rk mat t pr vide a static-free w rk surface. The mat is especially
useful when handling ESD-sensitive devices.
• Select a gr unding system, such as th se listed bel w, t pr vide pr tecti n that meets the specific
service requirement.
Note: The use f a gr unding system is desirable but n t required t pr tect against ESD damage.
– Attach the ESD gr und clip t any frame gr und, gr und braid, r green-wire gr und.
– Use an ESD c mm n gr und r reference p int when w rking n a d uble-insulated r battery-
perated system. Y u can use c ax r c nnect r- utside shells n these systems.
– Use the r und gr und-pr ng f the ac plug n ac- perated c mputers.
Grounding requirements
Electrical gr unding f the c mputer is required f r perat r safety and c rrect system functi n. Pr per
gr unding f the electrical utlet can be verified by a certified electrician.
S fety notices (multi-lingu l tr nsl tions)
The cauti n and danger safety n tices in this secti n are pr vided in the f ll wing languages:
• English
• Arabic
• Brazilian/P rtuguese
• Chinese (simplified)
• Chinese (traditi nal)
• French
• German
• Hebrew
4M75t Gen 2 Hardware Maintenance Manual

• Italian
• K rean
• Spanish
DANGER
Electrical current fr m p wer, teleph ne and c mmunicati n cables is hazard us.
To void shock h z rd:
• Do not connect or disconnect ny c bles or perform inst ll tion, m inten nce, or reconfigur tion
of this product during n electric l storm.
• Connect ll power cords to properly wired nd grounded electric l outlet.
• Connect to properly wired outlets ny equipment th t will be tt ched to this product.
• When possible, use one h nd only to connect or disconnect sign l c bles.
• Never turn on ny equipment when there is evidence of fire, w ter, or structur l d m ge.
• Disconnect the tt ched power cords, telecommunic tions systems, networks, nd modems
before you open the device covers, unless instructed otherwise in the inst ll tion nd configur tion
procedures.
• Connect nd disconnect c bles s described in the following t bles when inst lling, moving, or
opening covers on this product or tt ched devices.
To Connect To Disconnect
1. Turn everything OFF.
2. First, attach all cables t devices.
3. Attach signal cables t c nnect rs.
4. Attach p wer c rds t utlet.
5. Turn device ON.
1. Turn everything OFF.
2. First, rem ve p wer c rds fr m utlet.
3. Rem ve signal cables fr m c nnect rs.
4. Rem ve all cables fr m devices.
CAUTION:
When repl cing the lithium b ttery, use only P rt Number 45C1566 or n equiv lent type b ttery
recommended by the m nuf cturer. If your system h s module cont ining lithium b ttery, repl ce
it only with the s me module type m de by the s me m nuf cturer. The b ttery cont ins lithium nd
c n explode if not properly used, h ndled, or disposed of. Do not:
• Throw or immerse into w ter
• He t to more th n 100°C (212°F)
• Rep ir or dis ssemble
Dispose of the b ttery s required by loc l ordin nces or regul tions.
Chapter 1.Imp rtant safety inf rmati n 5

CAUTION:
When l ser products (such s CD-ROMs, DVD-ROM drives, fiber optic devices, or tr nsmitters) re
inst lled, note the following:
• Do not remove the covers. Removing the covers of the l ser product could result in exposure to
h z rdous l ser r di tion. There re no service ble p rts inside the device.
• Use of controls or djustments or perform nce of procedures other th n those specified herein
might result in h z rdous r di tion exposure.
DANGER
Some l ser products cont in n embedded Cl ss 3A or Cl ss 3B l ser diode. Note the following:
L ser r di tion when open. Do not st re into the be m, do not view directly with optic l
instruments, nd void direct exposure to the be m.
≥18 kg (37 lb) ≥32 kg (70.5 lb) ≥55 kg (121.2 lb)
CAUTION:
Use s fe pr ctices when lifting.
CAUTION:
The power control button on the device nd the power switch on the power supply do not turn off the
electric l current supplied to the device. The device lso might h ve more th n one power cord. To
remove ll electric l current from the device, ensure th t ll power cords re disconnected from the
power source.
1
2
6M75t Gen 2 Hardware Maintenance Manual

Chapter 1.Imp rtant safety inf rmati n 7

≥18 kg (37 lb) ≥32 kg (70.5 lb) ≥55 kg (121.2 lb)
1
2
8M75t Gen 2 Hardware Maintenance Manual

PERIGO
A c rrente elétrica pr veniente de cab s de alimentaçã , de telef ne e de c municações é perig sa.
Para evitar risc de ch que elétric :
• Nã c necte nem desc necte nenhum cab u execute instalaçã , manutençã u rec nfiguraçã deste
pr dut durante uma tempestade c m rai s.
• C necte t d s s cab s de alimentaçã a t madas elétricas c rretamente instaladas e aterradas.
• T d equipament que f r c nectad a este pr dut deve ser c nectad a t madas c rretamente
instaladas.
• Quand p ssível, utilize apenas uma das mã s para c nectar u desc nectar cab s de sinal.
• Nunca ligue nenhum equipament quand h uver evidência de f g , água u dan s estruturais.
• Antes de abrir tampas de disp sitiv s, desc necte cab s de alimentaçã , sistemas de telec municaçã ,
redes e m dems c nectad s, a men s que especificad de maneira diferente n s pr cediment s de
instalaçã e c nfiguraçã .
• C necte e desc necte s cab s c nf rme descrit na tabela apresentada a seguir a instalar, m ver u
abrir tampas deste pr dut u de disp sitiv s c nectad s.
P r Conect r: P r Desconect r:
1. DESLIGUE Tud .
2. Primeiramente, c necte t d s s cab s a s
disp sitiv s.
3. C necte s cab s de sinal a s c nect res.
4. C necte s cab s de alimentaçã às t madas.
5. LIGUE s disp sitiv s.
1. DESLIGUE Tud .
2. Primeiramente, rem va s cab s de alimentaçã das
t madas.
3. Rem va s cab s de sinal d s c nect res.
4. Rem va t d s s cab s d s disp sitiv s.
CUIDADO:
Ao substituir b teri de lítio, utilize pen s um b teri com Número de Peç 45C1566 ou um tipo de
b teri equiv lente recomend do pelo Se o seu sistem possui um módulo com um b teri de lítio,
substitu -o pen s por um módulo do mesmo tipo e do mesmo f bric nte. A b teri contém lítio e
pode explodir se não for utiliz d , m nuse d ou desc rt d de m neir corret .
Nã :
• J gue u c l que na água
• Aqueça a mais de 100°C (212°F)
• C nserte nem desm nte
Descarte a bateria c nf rme requerid pelas leis u regulament s l cais.
PRECAUCIÓN:
Chapter 1.Imp rtant safety inf rmati n 9

Quand pr dut s a laser (c m unidades de CD-ROMs, unidades de DVD-ROM, disp sitiv s de fibra ótica
u transmiss res) estiverem instalad s, bserve seguinte:
• Nã rem va as tampas. A rem çã das tampas de um pr dut a laser p de resultar em exp siçã
prejudicial à radiaçã de laser. Nã existem peças que p dem ser c nsertadas n interi r d disp sitiv .
• A utilizaçã de c ntr les u ajustes u a execuçã de pr cediment s diferentes d s especificad s aqui
p de resultar em exp siçã prejudicial à radiaçã .
PERIGO
Alguns pr dut s a laser c ntêm di d de laser integrad da Classe 3A u da Classe 3B. Observe seguinte:
Radiaçã a laser quand abert . Nã lhe diretamente para feixe a lh nu u c m instrument s óptic s e
evite exp siçã direta a feixe.
≥18 kg (37 lb) ≥32 kg (70.5 lb) ≥55 kg (121.2 lb)
CUIDADO:
Utilize pr cediment s de segurança para levantar equipament s.
CUIDADO:
O b tã de c ntr le de alimentaçã d disp sitiv e b tã para ligar/desligar da f nte de alimentaçã nã
desligam a c rrente elétrica f rnecida a disp sitiv . O disp sitiv também p de ter mais de um cab de
alimentaçã . Para rem ver t da a c rrente elétrica d disp sitiv , assegure que t d s s cab s de
alimentaçã estejam desc nectad s da f nte de alimentaçã .
1
2
10 M75t Gen 2 Hardware Maintenance Manual

Chapter 1.Imp rtant safety inf rmati n 11

1
2
12 M75t Gen 2 Hardware Maintenance Manual

Chapter 1.Imp rtant safety inf rmati n 13

1
2
DANGER
Le c urant électrique pr venant de l'alimentati n, du téléph ne et des câbles de transmissi n peut présenter
un danger.
P ur éviter t ut risque de ch c électrique :
• Ne manipulez aucun câble et n'effectuez aucune pérati n d'installati n, d'entretien u de rec nfigurati n
de ce pr duit au c urs d'un rage.
• Branchez t us les c rd ns d'alimentati n sur un s cle de prise de c urant c rrectement câblé et mis à la
terre.
• Branchez sur des s cles de prise de c urant c rrectement câblés t ut équipement c nnecté à ce pr duit.
• L rsque cela est p ssible, n'utilisez qu'une seule main p ur c nnecter u déc nnecter les câbles
d'interface.
• Ne mettez jamais un équipement s us tensi n en cas d'incendie u d'in ndati n, u en présence de
d mmages matériels.
• Avant de retirer les carters de l'unité, mettez celle-ci h rs tensi n et déc nnectez ses c rd ns
d'alimentati n, ainsi que les câbles qui la relient aux réseaux, aux systèmes de téléc mmunicati n et aux
m dems (sauf instructi n c ntraire menti nnée dans les pr cédures d'installati n et de c nfigurati n).
• L rsque v us installez, que v us déplacez, u que v us manipulez le présent pr duit u des
périphériques qui lui s nt racc rdés, rep rtez-v us aux instructi ns ci-dess us p ur c nnecter et
déc nnecter les différents c rd ns.
14 M75t Gen 2 Hardware Maintenance Manual