Morrow MDT 50 Service Manual Download Page 38 | Manualshive

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Summary of Contents for MDT 50

Page 1: ...MDT50 VIDEO DISPLAY TERMINAL SERVICE MANUAL...

Page 2: ...rwise without prior written permission of Morrow Inc DISCLAIMER No representations or warranties express or implied are made with respect to the contents hereof including but not limited to the implie...

Page 3: ...ooting Components Test Points Typical Waveforms Signal Levels 2 THE MAIN LOGIC BOARD Theory of Operation Test Points Typical Waveforms Signal Levels 3 THE KEYBOARD Theory of Operation Test Points Typi...

Page 4: ...5 MAINTENANCE The Monitor Unit General Replacing the CRT tube The Keyboard Unit MTC l MTC l MT l MTC 2...

Page 5: ...beam current AC 120V input and must lOT exceed 13 KV under any operating conditions To measure 2nd Anode Voltage use High Impedance meter Connect to chassis use a High Voltage lead from to 2nd Anode C...

Page 6: ...ations respectively as well as miscel laneous control and sequencing logic A Video Control board to convert Horizontal and Vertical synch pulses to the proper waveforms for controlling CRT raster scan...

Page 7: ...9 g o KEY BOARD WA009 CONTRAST 8S08 8509 8510 BVR501 LOGIC BOARD 8201 c 2 I 1 at 8202 B203 m B 06 m 8208 1 _ _ _ l 8405 I 8404 WA004 8204 I l34d7 Vv A008 L J POWER SUPPLY WADDS TRANSFORMER POWER UNIT...

Page 8: ...CHIP VllJliO AlJORESS SELECT ROW ADDRESS VIDEO CONTROL DELAY CKT CHARACTIIl GINERATOR t PARALLEL SERIAL SHIFT y 2 1 SELECTOR I CRT F CI l FcH r c T C 111V l FDOT I I I MONITOR I I l _ J t Fcpu TIMING...

Page 9: ...y Printer port also located on the rear of the Monitor Unit allows the Morrow MDT50 to be connected to any ASCII printer with an RS 232 serial interface Baud rates from 100 to 19 200 are available The...

Page 10: ...de all character data received from the keyboard is immediately transmitted to the Host hrough the Host Port but is not displayed on the CRT If it is in Half Duplex Mode character data received from t...

Page 11: ...onnect cable from Power Supply to Main Logic Board B404 Check B404 for Pin 1 Pin 2 Pin 3 Pins 4 S 12V DC O SV 1SV DC O 5V SV DC O 2SV Ground step 5 a If OK replace cable to Main Logic Board B404 B204...

Page 12: ...typical waveforms on Connector B208 a If OK Reconnect cable to Contrast Board B208 B508 go to Step 9 b Check all test points on Main Logic Board for proper signal levels and typical waveforms then is...

Page 13: ...o Board via Pin 4 of Connector BI03 It is used by IClOI muPC 1031 H2 to reset the beam of the CRT to the top of the screen in preparation for a scan After pulse shaping by ICIOl it is used to control...

Page 14: ...ge up to 12kV C Disconnect the Anode lead D Disconnect BI04 connector to Main Logic Board E Disconnect BIOI connector to CRT tube F Disconnect BI02 connector to small PCB on CRT tube G Disconnect BI03...

Page 15: ...ont of Monitor Unit and Rl02 Replace as necessary b If not found check Main Logic Board 4 Check for Video signal at TPl02 If found go to Step 9 S Check collector of TRl02 for 6 4V base for 0 4V and em...

Page 16: ...ard and the CRT tube actually connected Wiggle them to make sure 4 Main Logic Board Check Test Point TPI03 for Vertical Synch signal from the If no signal check Main Logic Board a If signal found go t...

Page 17: ...lace TRl03 4 Check TP107 collector of TR104 a If signal found go to Step 5 b Check base of TRl04 for 0 1 V collector for 18V and emitter for ground Also check T101 Replace as necessary c If signal fou...

Page 18: ...I I Fig 1 Fig 2 o 0 5V 100s VIDEO DIP TP1 be 0 5V 2ms VIDEO IIP v TP LL 1Y 2ms 3 I V SYN F _1 TP 04 _ J 2V 5ms DIP Fig 4_ R114 Y TP105 470 TP105 tuu O SY 10AJS Flg 5 1 H SYN _ TP r c I 50V 10AJS I Fi...

Page 19: ...cter data is also sent to U228 ACIA for transmission to the Host via Pin 2 of Connector B201 In Half Duplex Block and Local Modes data is not transmitted to the Host U209 68A45 CRT Controller controls...

Page 20: ...2 Monitor Dot Frequency CPU Clock 12V 0 5V 4 1V 0 5V 3 8V 0 5V nNE 05ps Df Y 0 265jJ S l I I I I I I I I I I I I I I IZV I I I I I I I I I I I OV i I TP209 U267 Pin 10 ACIA Clock RS232 Print Baud Rat...

Page 21: ...ical Output Signal 3 7V O 5V TP213 U232 Pin 3 CRTC Display Enable Output Signal I _ _ l 3 6V O 5V TIME 20JAS DIV 13J4S j 38 S 51p I I I I TlMt 20JAS DIV lIftS j 1 5 5 IJrS I I 7V J1 L n E 5MS DIV i 8...

Page 22: ...first putting the Address on the bus then strobing the address data into an Octal Latch U304 74LS373 with a 1 microsecond pulse on the ALE line Pin 11 The outputs of the Octal Latch are connected to t...

Page 23: ...SYNCHR ONOU5 IVPVr HORJZONTAL VID O BLANJ JNG 50 Hz 1 4 1 4 5 1 2 A S t Jl _1 I I I I I I I I I L 14 14 I p Ze WlS t 14 14 zo rn5 V R TtCAJ DRJV SVNCHRONOVS INPVr H 92ms V r nCAJ DR JV SYNCHRONOVS INP...

Page 24: ...5 or equiv voltage limited to 5V DC 1 A by U401 MC7805 or equiv and output on Pin 3 of Connector P404 Pin 4 is the OV reference ground for this power line Troubleshooting Components I Visual Check A T...

Page 25: ...circuit check R401 and R402 for open circuit 5 Remove and check Q402 power transistor us ing transistor checker Replace or repair wiring as necessary 6 Isolate and test Q401 with transistor checker Re...

Page 26: ...er 2 Check across C411 electrolytic for 15 0V DC If not found replace BR403 full wave rectifier and or Capacitor C411 3 Check for ground at Pin 1 of U403 and negative pole of C411 C412 C413 C415 and a...

Page 27: ...TPl TP2 TP3 It ms IV 9 7SV 1_1 r _______ __i _T V _ ZZ 25 V ZIV TP4 TP5 TP6 1 1 1 g ov lB J lV j 4 5V 2V 1 It W1S I Power Supply Board Loaded...

Page 28: ...e CPU Read Data Terminal 4V 0 5V 4V 0 5V 3 4V O 5V l It 17ms tl 8ms I I I I I I L H VI nI I I TIME Ims DIV I I I I W rr 14 z TIME 0 5 us 0 I V I I I I I JfV I_n I 1 4 3 2 Ls 1 l I 5 j I TiMlE 0 5 5 VI...

Page 29: ..._ _ _ _ TPl 1t 5V TP4 5V TP2 5Y TP5 zov 1 _ Z5V TP6 z V L _ Power Supply Board Unloaded...

Page 30: ...JC409 ua jDlJ jDlJ U403 U402 U401 8406 r J QS407 DO EC D EOO C412 8 Q403 C407 8 Q40 402 o I I I I M R403 R401 1 ol OR402 I mZ I l ii C406 C401 0 0 0 O N 8R402 N 8R401 V I t L _ _ J BR403 840 5 TillS S...

Page 31: ...25V OV 8LAC f 15VDC RED 1 1403 WHITE C406 C408 C409 4700u lOu 1251 0 1 u rv 35 OV BLACK U403 r ru I I 12V DC WHITE 2 31MC7912 I l __ J L __ C41 C 12 C 13 C414 415 470u 25 1u 35v 1OU 25 O lu 470u 25 V...

Page 32: ...reassembling the case It is recommended that signal levels and waveforms at all defined Test Points be checked whenever the Monitor Unit case is opened Starting with the Power Supply check signal lev...

Page 33: ...sture free compressed air every 3 to 6 months since it is exposed to environmental contamination dust dirt hair cigarette ashes spills paper shreds and dust etc While the Keyboard Unit is being cleane...

Page 34: ...PARTS LIST APPh 1 lX...

Page 35: ...tor Resistor Resistor Resistor Resistor Capacitor Capacitor Capacitor Capacitor Capacitor 1 68A02 68A50 68A45 68A21 6551 6116 2564 2732 74L500 74L804 74LS08 74L832 741S74 74L586 74L890 74L892 74L8107...

Page 36: ...pf 50v 68pf 50v 1N4148 18 432MH2 8 pin piano type 10 pin piano type 25 pin right angle 5 pin RTB 1 5 5 MICRO 7 pin JST 40 pin 28 pin 24 pin 62 5m m 208 209 210 211 212 213 214 215 216 217 218 219 220...

Page 37: ...0uf 16v C309 Capacitor 4 7uf 16v C314 49 K11109D Capacitor 1uf 16v C303 Capacitor 0 luf 12v C311 49 K11107C Capacitor 0 01uf 50v C305 306 C307 310 315 41 K23333C Capacitor O 033uf 50v C308 41 K23331C...

Page 38: ...13 41 K23104E Capacitor O luf 50v C404 409 414 1603 00022 Wafer GP SVF Base B405 1603 00004 Wafer 5P SVF Base B404 1603 00002 Wafer 3P SVF Base B406 407 1001 00015 Fuse 250V 1 5A FST F401 37622S000001...

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