Memotech Limited MTX 500 Wartungshandbuch

MTX Service Manual

6 Z80 CPU The instruction set contains 158 instructions. The 78 instructions of the 8080A are included

7 Pin description A0-A15. Address Bus (output, active High,·3-sta

8 IORQ. Input/Output Request (output, active Low, 3- state). IORQ indicates that the lower half of the

9 RFSH. Refresh (output, active Low). RFSH, together with MR

10 Z80 CTC The Z-80 CTC four-channel counter/timer can be programmed by system software for a br

11 Pin Description CE. Chip Enable (input, active Low). When enabl

12 INT. Interrupt Request (output, open drain, active Low). Low when any Z-80 CTC channel that has been

13 Z80 DART The Z-80 DART (Dual-Channel

14 Pin Description B/A. Channel A Or B Select (input, High selects channel B). This input defines which channel i

15 IEI. Interrupt Enable In (input, active High) is used wit

MTX 500/512 SERVICE MANUAL&TECHNICAL INFORMATIONMemotech LimitedWitneyOxon OX8 6BXTel: (0993) 2997Tlx: UK83372 MEMTEC GMTX Service Manual

16 RxDA, RxDB. Receive Data (inputs, active High). RESET. Reset (input, active Low). Disables both

17 TMS 9929 VDP (Video Display Processor) Introduction This Prel

184116VRAMPIN NAMESA0-A6 Address InputsCAS Column Address StrobeDIN Data InputDOUT Data OutputRAS Row Address Strob

19MTX Service Manual

20 MTX SERIES BUS The system Bus comprises the full Z80 A bus, power supply rails, ROMpak enable (GROM), RO

21 System Block DiagramMTX Service Manual

22 DISASSEMBLY INSTRUCTIONS 1. Using an Allen key, remove the three dome head screws from the right

23 The under side of the MTX reveals a single screw which secur

24MTX Service Manual

25 Introduction To Trouble Shooting Guide Memotech products a

CONTENTS Page Overall Description...

26 SYMPTOM 1 On power up:- No display or only a black and white display. a) Cause of Trouble Black and W

27 3 If still faulty replace the Modulator. c) Cause of Trouble

28 SYMPTOM 2 When power is switched on: Blank screen - no humming sound. a) Cause of Trouble Faulty video

29 Repair Method 1 If pulse is absent on 4Mhz Xtal - follow

30 SYMPTOM 3 Corrupt video display or characters a) Cause of Trouble - 5v absent Check Point

31 may pick out the faulty component. c) Cause of Trouble

32 b) Cause of Trouble Faulty Bridge Rectifier Check Point Check your +5v and +12v Repair Method

33 a) Cause of Trouble Faulty voltages Check Point C

34 Repair Method 1 If any address signal is absent - Reset MTX whilst probing. If signal is still abse

35 NB: We find it helpful to replace all the socketed IC's wi

Timing Chain...46 Rear Plastic moulding...48 PARTS LIST...

36 Check Point By typing LO."" (RET) and loading in a long playing cassette tape start prob

37 d) Cause of Trouble MTX 512 with internal expansions only C

38 4 If pulse is present on both 4E (374) and 5E (SN76489AN) check for pulse on pin 1 of J13 on pal b

39 Repair Method Generally key bounce is caused by faulty key board

40 SYMPTOM 9 Add on faults - e.g. Memory expansions, Rom boards, RS232, Printers etc. a) Cause of Trouble

41 4 Check links 6 and 7 on MTX. 5 Look closely at the 273 (5A) o

42 Further information on the UM 1286 Modulator. The Pal-Modulator is used to encode the R-Y, B-Y and Y signals from the MTX hom

43 Test and setting procedure of UM 1286 and video board 1 Be sure that

44 Link arrangements and PAL colour coding 1. MTX 500 - 4000/04 with 32k H Ram chips. _

45 PROM CODE FOR MEMORY EXPANSION BOARDS MTX 500 CODE DESCRIPTION

1 INTRODUCTION Overall Description

46 Timing chain modification In October 1984 Memotech altered the timing chain circuitry due to occasional faults occurrin

47MTX Service Manual

48 Plastic back panel. You will find that your TV/Monitor picture will tear or wobble if your plastic back panel does not have:

49 PARTS LIST FOR THE: MTX 512 04

50 MTX LOADING STAGE 1. MEMOTECH ITEM DESCRIPTION NO./ PCB COMPONENT LOCATION PART NO. UNIT

51 CAPC NF0047 47pf Ceramic Disc Cap 1 C14 CAPE A470016 4700uf 16

52 CRXL 4.000 4.000 MHz Crystal 1 XTAL1 DODE IN4004 IN4004 Silicon Diode 4 D14,D16,D18,D19 DODE IN4148

53 MDOR UM1286 UM1286 Modulator 1 MODULATOR RES 033R 33

54 ICMO Z80ACTC Z80A CTC 1 IC6 ICPA 14L4 PAL 14L4-2CN 1 IC4 ICRO 38128A ROM 16B MSM

55 ICMO LM1889 LM1889 1 IC3 IDTA UH004.7 4.7UH Axi

2 CPU Board Mounted in the lower chassis, the CPU board accommodates: Z80A CPU operating

56 MTX KEYBOARD MEMOTECH ITEM DESCRIPTION NO./ PCB COMPONENT LOCATION PART NO. UNIT /

57 KYTP 6011F & - 6 1 KYTP 6153F 6 - DEL

58 KYTP F663F F3 1 KYTP F664F F4 1 KYTP F665F F5 1 KYTP F666

59 KYTP Q000F Q 1 KYTP R000F R

60 MTX REAR PLUG ASSEMBLY MEMOTECH ITEM DESCRIPTION NO./ PCB COMPONENT LOCATION PART NO. UNIT

61 BOX MTX512 MTX 512 Box 1 CONP J23.5 23.5 Cable Jack Plug

62 MTX RS232 I/F MEMOTECH ITEM DESCRIPTION NO./ PCB COMPONENT LOCATION PART NO. UNIT

63 RS232 I/F TESTING MEMOTECH ITEM DESCRIPTION NO./ PCB COMPONENT

64 32K MEMORY EXPANSION MEMOTECH ITEM DESCRIPTION NO./ PCB COMPONENT LOCATION PART NO. UNIT

65 TLS ALLK2MM 2MM Allen Key 1 ROM EXPANSION MEMOTECH ITEM

3 Graphics Facilities Up to 32 independently controllable user definab

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71RING SYSTEMThe MTX ring uses channel A of the dart. If the ring is installed, the bau

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4 NODE/RING SYSTEM Communications software and interfacing enabling construction of MTX Ring Systems. The system

5 mouldings are incorporated in the PSU casing to support the