AMSTRAD PPC 640D User manual

PPC512S/512D

PPC 640S /640D

PERSONAL

PORTABLE COMPUTER

SERVICE MANUAL

CONTENTS

Technical Specification

Important Notes to Service Engineers

FD-5 Maintenance and Alignment Information

Exploded View 1

Exploded View 2

Circuit Board Views

Alignment Instructions

FD-5 Control Board Schematic Diagram

Cabinet Drawing &Parts List

CPU/Switch/Battery P.C.B.'s

Memory/Fuse/Volume P.C.B.'s

Modem P.C.B. Component Layout

Keyboard Schematic Diagram

Chassis Schematic Diagrams

Power Supply Schematic Diagram

Modem Chassis Schematic Diagrams

Electrical Parts List

Page TECHNICAL SPECIFICATION

2PPC640

2•Parallel Centronics Printer Port

3—11 •Compartment for 1Alkaline CCells to give up to 8hours use.

•8086 16-bit processor, 8MHz clock.

13 •640k Ram, 64k Video Memory.

14 •Integrated display adaptor fully compatible with MDA and CGA.

14 Drive either the LCD panel or an external monitor.

•640 x200 pixel supertwist LCD panel supports all CGA and

MDA graphics and text modes. Display can be tilted to 6

viewing angles and contrast is fully adjustable to allow for

18, 19different lighting conditions.

20 •Integral Modem which supports

21 V21 (300 bps) Full Duplex

22 —25 V23 (1 200/75bps)

26 V22 (1200 bps) Full Duplex

27, 28 V22bis (2400 bps) Full Duplex

29 —31 •Hayes Command compatible; auto-dialling, auto answer

•Includes Serial Port.

•AC Mains Adaptor.

•Enhanced AT type keyboard with 102 keys.

•Single or Twin 720K 31/2 inch Disk Drives.

•Microsoft MS-DOS 3.3 Operating System.

•Mirror II Communications Software.

•Built-in Super Twist, 640 x200 resolution, with grey scale

emulation; hardware to drive any external CGA monitor.

•Speaker with volume control.

•Battery backed real time clock with scratchpad RAM. -^0

•Socket for 8087 maths co-processor.

•Socket for PPC640 expansion box (to accept IBM compatible

expansion cards and hard disk).

•Carrying case with pockets for manual and disks.

•Carrying size closed:

Length: 450mm (1 73/4") excluding handle.

Depth: 230mm (9")

Height: 100mm (4")

Weight: 5.4Kg (1 13/4lb) excluding batteries.

PPC512

•PPC512 specification as PPC640 but with 51 2K Ram and

without integral modem and Mirror II Communications Software,

•Single or Twin 720K 31/2 inch Disk Drives.

IMPORTANT NOTES TO SERVICE ENGINEERS

This Service Manual gives indepth technical information on all of the circuits and the P.C.B.'s which make up the PPC51 2/

640. Much of this data is for information purposes only as the procedure engineers will follow when servicing this equip-

ment will often be to exchange Printed Circuit Boards. In some instances Amstrad will insist that subassemblies are

returned for exchange and should not be serviced by Service Engineers.

Please take note of the following information before attempting to the service the equipment.

Full diagnostics are not specified in this manual. Adiagnostic tool, designated the R.P.5-2*, is available from CPC and gives

certain diagnostic information on the Computer. To carry out any indepth fault-finding this diagnostic tool is necessary.

2. The Disc Drive Mechanism and accompanying Printed Circuit Boards should not be serviced by Service Engineers. Exchange

mechanisms complete with P.C.B.'s are available from Amstrad.

3. LCD Supertwist is acomplete unit, and no service should be attempted on this unit by the field engineers. Exchange Display

Assembly should be obtained from Service Department.

4Complete Printed Circuit Boards are available on an exchange basis and unless the Service Engineer is particularly familiar

with this product arrangements should be made to exchange the P.C.B.'s where afault has developed. The R.P.5-2 diagnostic

referred to above can be used to ensure correct diagnosis of the P.C.B. fault.

5. In some instances asecond Disc Drive will be fitted to the PPC-51 2/640. This second Disc Drive is subject to seperate service

information but under no circumstances should any service work be carried out on the mechanism or its Printed Circuit Board.

In the event of afault on the second Disc Drive arrangements should be made to exchange this.

6. Service Engineers carrying out any repairs on this unit can contact the Customer Services Section of Amstrad for further infor-

mation should they have any difficulty.

The PPC51 2/640 is asophisticated piece of computer technology and service work should be undertaken on this equipment by

suitably qualified personnel and preferably by appointed Amstrad Agents.

'Upgrade kit is available to enable full diagnosis of the said machine.

FD-5 MAINTENANCE AND ALIGNMENT INFORMATION

(FOR INFORMATION PURPOSES ONLY)

1. OUTLINE OF MAINTENANCE

•The following tools are required for maintenance of aFloppy Disk Drive

1.1 Alignment Diskettes

Alignment diskette is used for head actuator alignment and index sensor alignment. Use the JU-01AA -DD and

817-363CE.

1.2 Exerciser

The exerciser enables you to make all adjustments and inspections necessary for an FDD. Its functions include the

following:

(1) Seek increment or alternate tracks

(2) Read (but no data compare)

(3) Write 1For 2F (All O's or 1's)

(4) Recalibration to track 00

The exerciser has switches and indicators to execute aspecified function.

2. DIAGNOSTIC PROCEDURES

2.1 Error Symptom Recognition

Errors that occur because of the wrong operating procedure, wrong programming, or use of adefective diskette, or soft errors

due to external causes, such as contaminated air and random electrical noise, are often attributed to adrive failure.

Unless avisual inspection of the drive reveals an evident assembly fault or adefect, always confirm errors with another

good diskette, and another known good drive.

2.2 Soft Error Detection and Correction

Soft errors are normally caused by the following:

(1) Contamination between read/write heads and diskette. This kind of contamination can be easily eliminated by the liner in

the diskette. Contaminated heads can be cleaned by ageneral purpose non-abrasive head cleaning diskette. Please follow the

suitable procedure provided with the cleaning diskette.

(2) Random electrical noise, normally afew microseconds or less.

(3) Small defects in written data and/or track not detected during write operation may cause soft errors during read.

(4) Faulty grounding of the drive or host system can also cause asoft error.

(5) Wrong motor speed is another cause of soft errors.

Take the following steps on the controller side to recover from the soft errors mentioned above.

(1) Read the track again ten times or until the data is recovered.

(2) If Step (1) above fails to recover the data, access the adjacent track. Then return the head to the original track.

(3) Repeat Step (1).

(4) Any error that cannot be corrected by the above procedure is irrecoverable.

2.3 Write Error

If an error occurs during write operation, it is usually detected during the next revolution by performing aread operation called

write check. To correct an error, write again and repeat awrite check operation. If the result is unsatisfactory after ten or more

write operations, perform aread operation on another track to determine whether it is the diskette or the drive that is wrong.

If an error persists, replace the diskette and repeat the above procedure. If the error still persists, consider the drive defective. If

the error is corrected, dispose of the diskette as defective.

2.4 Read Error

Most read errors are soft errors. Data can be recovered by following the recovery procedure mentioned in 2.2.

2.5 Seek Error

(1) Stepper motor or stepper motor circuit drive is faulty.

(2) Faulty Carriage

There are two ways of seek error recovery. One is to recalibrate to track 00, and seek back to the original track. The other is to

read the ID field, check the track number on which the head is located, and move the head away from it. And read it

again.

2.6 Interchangeability Error

Data which is written by one drive may not be read by another. This error is called an Interchangeability error, which can be

caused mostly by the following reason, which should be checked as follows.

(1) Head misalignment: Refer to Adjustments and Confirmation Item 5.5

(2) Head output too low: Refer to Adjustments and Confirmation Item 5.3

(3) Motor speed difference: Refer to Adjustments and Confirmation Item 5.1

(4) Format difference

3. TROUBLE ANALYSIS

3.1 Trouble Analysis Procedure

FDD trouble may occur in any of the following nine forms.

(1) Index detection failure

(2) Not ready

(3) Track undetectable

(4) No seek

(5) No write

(6) No read

(7) Read error

(8) IN USE LED won't light

(9) Write protect undetectable

CAUTION:

Be sure to switch power off before removing an FDD or PCB from the operating system.

3.1 TROUBLE ANALYSIS TABLE

Item Trouble No. Cause JU-3X2, 252A, 253A

1Index Detection Failure 1DD motor control PCB Replace DD motor assembly

2DD motor faulty Replace DD motor assembly

3Index LED faulty Replace

4Index detector faulty Replace

5PCB motor ON circuit Repair

6PCB index detection circuit Repair

2Not ready 1See Item 1

2PCB ready circuit Repair

3Track detection failure 1Track 00 assembly Replace

2PCB track detection failure Repair

4No seek 1Stepper motor Replace

2Guide shaft contamination or damaged Replace

3PCB stepper driver circuit Repair

5No WRITE 1See Item 1

2Head disconnected Replace

3Head shorted Replace

4PCB write circuit Repair

6No READ 1See Item 1

2See Item 5

3PCB read circuit Repair

7READ ERROR 1See Item 1

2See Item 6

3Alignment Adjust

4Azimuth Unadjustable

5Burst Unadjustable

6Asymmetry

7Limiter Adjust

8FlagO Adjust

9Index period Replace DD motor assembly

10 PCB read circuit Repair

8IN USE LED won't light 1LED part Replace

2PCB IN USE circuit Repair

9Write protect failure 1Write protect part Replace

2Write protect circuit Repair

4. PREVENTIVE MAINTENANCE

No preventive maintenance is necessary for any type of FDDs under normal conditions of use.

However if it is determined that adjustments are necessary, the following must be done.

•Adjustments (Refer to table 4.1)

(1) Specify an applicable model from Table 4.1, and make aread/write head radial adjustment at aspecified track.

(Sides 0,1)

(2) Make an index timing adjustment at aspecified track. (Sides 0,1).

(3) Make an azimuth measurement at aspecified track (Sides 0,1)

CAUTION

Do not write when using alignment diskette. Check that write protect sensor is properly operating with adata diskette.

Note: Section 9describes the adjustment procedures in detail.

5. ADJUSTMENTS AND VERIFICATIONS

5.1 Motor Speed Verification (Index Period)

(1) Insert adiskette, run the motor, and clamp. Refer to the index period column of Table 4.1 for the applicable model.

(2) Step to the specified track.

(3) Connect afrequency counter to the INDEX signal.

IX (INDEX)

(4) Check that the frequency counter readings meet the specifications in the table.

5.2 Write Protect Verification

(1) Check that the exerciser's write protect lamp goes on and off as amedia is inserted and removed as specified in the

table below.

Media with write protect hole open: ON

Media with write protect hole closed: OFF

5.3 Head Output Verification

Use anew diskette if possible to identify head failure for this check.

(1) Insert agood diskette.

(2) Run the motor.

(3) Step to the track specified in the output level column of Table 4.1.

(4) Connect the oscilloscope probe as specified below.

CH1 :T1

CH2 :T2

EXT :IX (Index)

Invert channel 2 and select the Add mode.

Set vertical deflection to 10mV/division and horizontal deflection to 20ms/division.

(5) Write 2F (all ones) on the entire circumference.

(6) Check that the average output level meets the specifications of Table 4. 1.If it does not meet the spec-ifications, refer to item

7of the Trouble Analysis Table.

5.4 Output Modulation Verification

Modulation: Mis calculated by the following formula.

M(%) =Vmax -Vmin x100 using the value obtained in 5.3, and check that the calculated value is 20% or less.

M(%) =Vmax +Vmin

]

Maximum Voltage Value :Vmax

Average Voltage

Minimum Voltage Value :Vmin

Fig. 5.1 Modulation

3.2 Trouble Shooting Flow Chart

(

Run the operating system and

check. Record all diagnostic

information on tracks and sectors

as far as the program permits.

Install Exerciser on FDD

Power SW

DCSWON MOTSWON

Drive Select SW

YES

Set Address SW to Track

YES

Write SW ON

YES

Write SW OFF

YES

FDD online test

rCheck Item 4,

Table 3.1

NO Check Item 5,

Table 3.1

Check Item 6,

Table 3.1

5.5 Radial Alignment Adjustment

Introduction

This adjustment is normally not necessary.

If the mounting screws for the steeper motor loosen, or if parts become defective, or if acompatibility error occurs, check and

readjust according to the following procedure.

Steps (4) and (9) below should be performed regardless of the type, CE or DAD alignment diskette used. Use an alignment dis-

kette suitable to the type of FDD to be adjusted according to table.

(1) Insert an alignment diskette.

CAUTION:

Be sure to leave the alignment diskette under room conditions for 20 minutes before adjustment.

(2) Step to the track specified in the Radial alignment column of Table 4.1.

(3) Leave the oscilloscope in the same condition as mentioned in section 5.3.

•Cats Eye System

(4) Check the output waveforms for sides and 1. They should appear as in Fig. 5.2.

(5) The two waveforms should appear in the amplitude ratio in the R/A +/- 42% or more.

(6) If the specified ratio is not satisfied, loosen the two mounting screws for the stepper motor.

(7) Move the stepper motor along the base by hand until the two waveforms assume approximately the same amplitude, and

retighten the mounting screws. (See Fig. 5.2).

(8) Step the head outward (track 0) and inward (track 40 or 79), and confirm that the adjustment has been completed.

(9) After the intitial adjustment, be sure to confirm track 00 sensor adjustment 5.8 and carriage limiter 5.9.

lI/1l

-1/s. -

U-44-

U- III 1i-W-C li-U- 1II

-M Mi-4-U

->'-

,1 ''

- -

A>B

8>A

X100

X 100

Fig. 5.2 Radial Alignment Waveforms (CATS EYE)

Note: Alignments on sides and 1are adjusted at the factory. If they are misaligned, adjust

them to meet the specifications of Table .

DAD (Dynamic Alignment Diskette)

(4) Watch the output waveforms for sides and 1. They should appear as shown in Fig. 5.3.

(5) Measure the timing levels A1 to A4 and B1 to B4 in Fig. 5.3., and calculate the lobe ratio from the following

formulas.

LA >SB ZB x100%

LA LA (SB :LA x100%

(6) The lobe ratio calculated by the above formulas should meet the specifications on item 3of Table.

(7) If the above requirement is not met, loosen the two mounting screws for the stepper motor, adjust.

(8) Seek from track to track 40 and from track 79 to track 40, and confirm that the adjustment has been completed.

(9) After the radial adjustment, be sure to confirm track 00 sensor adjustment 5.8 and head carriage limiter 5.9.

Note: An alignment instrument for 3.5 inch FDDs permits accurate and easy adjustment

because the lobe ratio is displayed on the instrument.

~]fAzimuth

waveforms

Index

burst

waveform

20 ms |

"IT

Radial alignment waveforms

70 ms 120 ms 170 ms

Fig. 5.3 Alignment Waveform (DAD)

5.6 Azimuth Verification

(1) insert an alignment diskette. Seek to the track specified in the azimuth column of Table 4.1.

(2) Set the oscilloscope in the same conditions as in 5.3., and set horizontal deflection to 2ms/div (DAD) or 0.5 ms/div

(CE).

(3) Measure as shown below.

(4) Confirm that the measured value meets the specifications in the azimuth column of Table 4.1.

Ui LAI

Azimuth 0' waveforms

Case of B>C (+)

B—C

Azimuth =-x(A)

B—u

(A) :CE—30'

DAD— 15'

Case of OB(-)

C—B

Azimuth *- x(A)

Fig. 5.4 Azimuth Waveforms

5.7 Index Burst Verification and Adjustment

(1) Insert an alignment diskette. Seek to the track specified in the l/B column of Table 4.1.

(2) Set the oscilloscope time base as follows: 1ms/division.

(3) Check that the time from oscilloscope start to the first data pulse meets the l/B specifications of Table 4.1. (DAD

SYSTEM).

Index Burst

Fig. 5.5 Index Timing

5.8 Track 00 Sensor Adjustment

(1) Set the oscilloscope as follows:

Set horizontal deflection to 1ms/division.

CH1 :ZP

EXT :SP

(2) Step between specified tracks at in the FLAG item of Table 4.1 .(Turn the seek delay switch on the exerciser to adjust

12ms seek).

(3) Loosen the track sensor screw and adjust until the waveform on the oscilloscope appears as shown in Fig. 5.6.

ADJUST A: BTO 1:1

Fig. 5.6 Track Waveform

5.9 Limiter Verification

(1) Seek to track 0.

(2) Write 2F data on track 0, and measure read level.

(3) Seek to track -1, and check that the head just touches the limiter.

(4) Check that, when the RECAL switch on the exerciser is pushed ON, the head returns to track and that the 2F output level

is the same as that measured in Step (2).

Fig. 5.7 Asymmetry Waveform

(Asymmetry Wave form might be reversed up-and-down from model to model )

5.10 Asymmetry Verification

(1) Insert adata diskette.

(2) Step to the track specified in the symmetry item of Table 4.1.

(3) Set the oscilloscope as follows:

CH1 :RD

CH2 :T1

Set time base to 1us/division and vertical deflection to 0.2 v/division.

(4) Write 1F.

(5) Aread wave form is displayed on the oscilloscope as shown in Fig. 5.7.

(6) Confirm if it satisfies the value as shown in Table 4.1.

(Asymmetry wave form might be reversed up-and-down from model to model).

ALIGNMENT CASSETTE

3.5 inch Alignment Diskette

TP1 P/N Index Burst Azimuth Radial Alignment MODEL

135 DAD

135 CE

JU-01AA

817-363CE

40TRK 40TRK 40TRK JU-252A

JU-253A

MEASUREMENT ITEMS TABLE 4.1

Item Parameter JU-252A, 253A

TRK Value

1Index Period 40 200 ±2ms

2Output Level 79 80mV or more

3Radial Alignment

Reference (DAD)

Reference (CE by 817-363CE)

40 ±35(im

(29% or more)

(42% or more)

4Azimuth 40 ±24'

5Index burst 40 3± 1.7ms

6FlagO From track to track 1

and back TROO (TROO: Low, Tr1 :Height)

7Limiter -1 Recalibrate and return to

8Asymmetry 79 <700NS

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