Tandy CM-4 Service Manual Download

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Summary of Contents for CM-4

Page 1: ...TANDY8 Service g s rv i W K s V P h S V r v yrtj ix f r tnzi iii Ss sSi COLOR MONITOR CM 4 Catalog Number 25 1021 Iks i fe2 v 8i5 S x ...

Page 2: ...LIGNMENT INSTRUCTIONS 14 TROUBLESHOOTING GUIDE 18 P C BOARD Top and Bottom Views CRT Socket PCB 22 LED PCB 23 Main PCB 23 WIRING DIAGRAM AND PARTS LOCATION 27 CABINET EXPLODED VIEW PARTS LIST 1 Cabinet Exploded View 28 2 Electrical Parts List 29 3 Cabinet Parts List 39 SCHEMATIC DIAGRAM 41 WAVEFORMS 44 SEMICONDUCTOR LEAD IDENTIFICATION 44 ...

Page 3: ... 30 fl min at intensity white 8 Display color 1 5 colors 9 High voltage 23 kV O A 27 5 kV maxJOfJK 10 Picture linearity a Horizontal 10 max b Vertical 10 max 11 Synchronous Pull in range a Horizontal 15 701 kHz i b Vertical 60 Hz 12 Dot Pitch 0 64 mm NOTE Nominal specs represent the design specs all units should be able to approximate these some will exceed and some may drop slightly below these s...

Page 4: ...the rated value no higher Operation at higher voltages may cause a failure of the picture tube or high vol tage circuitry and also under certain conditions may produce radiation in excess of desirable levels 4 When the high voltage regulator is operating proper ly there is no possibility of an X radiation problem Every time a color chassis is serviced the bright ness should be tested while monitor...

Page 5: ...ts in display moni tors have special safety related characteristics These characteristics often pass unnoticed and the protec tion afforded by them cannot necessarily be obtained by using replacement components rated for higher vol tage wattage etc Replacement parts that have these special safety characteristics are identified in this manual electrical components having such features are identifie...

Page 6: ... collectors of the output tran sistors Q851 Q861 Q871 When the horizontal output circuit is operating pulses are developed and fed to the 1 16V supply where they are applied to a winding of the horizontal output transformer T602 This pulsed DC voltage is then taken from terminal s of T602 and applied through D71 7 and R865 or R866 or R867 to the collectors of Q851 Q861 andQ871 respectively The bri...

Page 7: ...orizontal drive circuit The pulse switching mode of the driver and output stage is a reverse polarity type that is when the driver transistor Q601 is ON the output transistor Q602 is OFF 5 Horizontal Output and HV Rectifier Figs 3 5 Horizontal drive voltage developed at pin 6 of the deflection processor integrated circuit IC601 is am plified through the horizontal drive stage Q601 and coupled to t...

Page 8: ...uit of Horizontal Output Circuit I IR71 18V H W C72izt 714 R717 T TO CRT SECOND ANODE TO CRT FOCUS TO CRT SCREEN TO ABL CIRCUIT 145V To Blanking and orizontal AFC DET Circuit TO CRT Heater THIS AREA IS COLD GROUND D713 AAV p f 18V Figure 5 Horizontal Output and HV Rectifier Circuit ...

Page 9: ...ith SW701 set in the ON position AC voltage is ap plied through a Bridge Rectifier circuit A conventional type Automatic Degaussing circuit consisting of a positive coefficient thermistor PR701 in series with the degaussing coil assembly L701 is used The AC input voltage is rectified by the Bridge Rectifi er circuit D701 D702 D703 D704 and then applied to the Regulator circuit A switching type Reg...

Page 10: ...1 R716 D713 12V Regu lator R401 116V 18V 12V 5 1 V R481 Figure 7 Block Diagram of Power Supply PR701 Cwv I L701 ADG O C 33 33 m Figure 8 ADG Circuit TIME ROM BRIDGE gj OUTPUT RECTIFIER T v ve D ul SCR STARTER HORIZ 3 XFMR 3T SCR701 TO COLLECTOR OF Q602 mm REGULATED OUTPUT 116 r p 1 SCR DRIVE I i i PHASE DETECTOR ERROR AMP I REFERENCE VOLTAGE F REGULATOR IC IC701 r4 Figure 9 Block Diagram of Regula...

Page 11: ...AC120V 60Hz C716 C714 145V D717 Figure 10 Power Supply Schematic ...

Page 12: ...ack trans bracket and disconnect the connector K Figure 11B 5 Disconnect the connectors NA and M on the PCB A main PCB A 6 Loosen the wire holder fixing power switch lead CRT ground lead RGB output lead Degaussing lead and LED lead Figure 1 1B 7 Remove the PCB A main PCB from the front cabinet 3 Remove screw 5 for PCB C the LED and also PCB C from the front cabinet Figure 1 1B Note When servicing ...

Page 13: ... Hi 5 8or J CD O O o rr o Li CO o o o H O ffl i t q LU 1 o a o X FH rr or a C o V o H H 0 z o oc tr C V LU LU i CO X or UJ cm co tu i M o uj o i a O Z M w O o uj _ t aj z M r 10 Z 3 0 UJO 0E OZh WO x 5 On X Q O z o CM hi coo t x 1 N UJ _ M Oo o w co cd o or Oh x a CM O 2 o u jhl o ox io uj 2 o o x oe UJ h q uj CM s z CM cm z a o w o o o b o o o o o o o o Si v co M CO CM 1 iri x 00 c o LU Q Q UJ O ...

Page 14: ...perate the display Monitor for at least 1 5 minutes at 1 20VAC line voltage with the computer display ing high intensity white pattern 2 Turn off Switch SW851 on PCB B 3 Rotate the screen control on T602 to the maxi mum counterclockwise end of its rotation 4 Connect an accurate high voltage meter to the CRT anode Check that the reading is approximate ly 22 0kV and 23 0kV at beam current If a corre...

Page 15: ... clamp screw and pull the deflection yoke as close as possible to the pu rity and convergence magnets assembly 7 Begin the following adjustment with the tabs on the round purity magnet rings set together Initial ly move the tabs on the round purity magnet rings to the side of the CRT neck Then slowly separate the two tabs while at the same time rotating them to adjust for a uniform green vertical ...

Page 16: ...3 at both ends of R407 9 Turn the brightness control in either direction to check that the picture maintains a good white balance 10 Repeat steps 3 thru 9 for readjustment 10 Static Center Convergence Figs 13 16 1 Switch the display monitor ON and allow it to warm up 15 minutes 2 Operate the computer in such a way that the en tire screen is a Crosshatch pattern display period 44 698 fiS horizontal...

Page 17: ... deflection yoke up and down Insert tilt ad justment wedges T and 5 between the deflec tion yoke and the CRT until the misconvergence illustrated in Figure 17 has been corrected 4 Tilt the deflection yoke right and left Insert tilt ad justment wedge 3 between the deflection yoke and the CRT until the misconvergence illustrated in Figure 18 has been corrected 5 Alternately change the spacing betwee...

Page 18: ... anode to the gate of SCR701 Is the power circuit activated i J D705 1 1 1 Yes D716 i i i No Connect a resistor 15W 50 ohms between TP 91 and T702 to D7 16 junction Is the horizontal sync circuit activated No Yes Does 18V appear between pin S of IC701 and ground No Yes Does 7 8V appear between pin 7 of IC701 and ground No R615 D605 IC601 R613 t Q601 R620 i Q602 D603 I D602 JR717 R719 D714i R716 D7...

Page 19: ...al appear No Input circuit computer Yes UUca J tv d J Jcai at the emitter of Q402 No 1 r V Input circuit computer G401 G402and its related Circuits ZY77 R413 f Q401 I Q402 D407 i I D408 Circuits Checked Video circuit and its related circuits NO PICTURE APPEARS Note If the picture does not appear fully rotate the brightness contrast control clockwise before inspecting Check the video signal at the ...

Page 20: ... 1 adjustment is not a But horizontal synchronization is normal The vertical sync frequency car varied slightly 1 _ _ 1 1C601 R513 1 R510 R514 1 R511 C503 1 R512 C505 L be VERTICAL SWEEP DOES NOT OCCUR Circuits Checked IC601 and its related circuits Q501 and Q502 and their related circuits Apply a ripple current signal across a resistor 1 Kohm and capacitor 10 F in serial connection to pin 2 of IC...

Page 21: ...ed in green or magenta Check the red video circuit Q451 Q851 The raster is colored in blue or yellow Check the green video circuit Q461 Q861 Check the blue video circuit Q471 Q871 IC491 C850 l IC492 C856 IC493 R865 IC494 R868 i Q451 R856 Q851 R862 C451 R850 C853 IC491 IC492 IC493 IC494 Q461 R851 R866 R869 C461 C851 C857 C854 I Q861 I R863 IC491 R870 IC492 C471 IC493 C852 IC494 C855 Q471 R852 Q871 ...

Page 22: ...d from the top side U S A up to 55050 CANADA up to 7004 U S A 55051 CANADA 7005 R BIAS 0R862 G B1AS B BIAS Q R863 Q R864 R ORIVE R85a 9 R BIAS Q R862 G BIAS QR863 B BIAS R864 R DRIVE Rasa QR856 BZg SvE 8b H It RT Socket PCB Bottom View U S A up to 55050 CANADA up to 7004 U S A 55051 CANADA 7005 R858 R DRIVE 0B DRIVE R856 22 ...

Page 23: ...LEDPCB Top View Main PCB Top View U S A up to 55050 CANADA up to 7004 fF4 6SCg W TDK DX TlSVffiClM I LED PCB Bottom View IF4I65CE fl T0K TI5V 23 ...

Page 24: ...DA 7005 TU B 73 R4S3 R493 I R 22 j W_CONTRAST v sizE r r i IN I Q422 8 A lg JLo T j TS j V j CS02 cy t L ST R6I2 R50S C620 S j JCAUTION FOR CONTINUED PROTECTION I AGAINST A RISK OF FIRE REPLACE ONLY WITH SAME TYPE ISA I2SV FUSE 1 I o 24 ...

Page 25: ...J r ai rnnw FOR continued protection against a risk of fire r OAU I lUrSi REpLACE 0NLY WITH SAME TYPE 4A I25V FUSE 1 FT L49I mJ L492 LsaJ L493 jui 1 J 495 o jy R484 R4B3 j B48S 0491 SW30I V CEWTEH r D49Z JL 3 2 p D493 D494 D495 P496 R49I 4 IS J BLACK BLUE WHITE f l F s F70I 4A 125V 25 ...

Page 26: ... _FOR CONTINUED PPOTECT10N AGAINST A KKK I 5 1 R468 ADJ 1 utu T 5 0471 TS 0461 1 Icaution ss gggggjagsg jTOJgyMr iiiiiii iiin ET O Oktoi If iff M P4 I SWSOI V CEMTEH 0498 J 3 z l p Td4 0494 j 7m s g S doe 5 v J I 4 9 this K4I63QAI 1F4I63CEI A 26 ...

Page 27: ...WIRING DIAGRAM AND PARTS LOCATION Q Z a o z ft O Q z z LU 111 P P a z a o z tt Q Q Z Z UJ UJ A oo uj i g D O O QZ OO I r t rj ujuj 27 ...

Page 28: ...1 Cabinet Exploded View CABINET EXPLODED VIEW PARTS LIST Mark U S A 21988 55000 Mark U S A 21988 only Mark CANADA only jo 3 28 ...

Page 29: ...81 Electrolytic 220 xF 16V 20 CC227MDAP VCEAGA1CW227M C482 Ceramic 0 0 VF 50V 80 20 CC103ZJCP VCKZPA1HF103Z C483 Ceramic 820pF 50V 10 CC821KJCP VCKZPA1HB821K C484 Electrolytic VF 50V 20 CC105MJAP VCEAAA1HW105M C491 Ceramic 0 VF 25V 80 20 CC104ZFCP VCTYPU1EF104Z C492 Electrolytic VF 50V 20 CC105MJAP VCEAAA1HW105M C493 Ceramic O VF 25V 80 20 U S A 21988 CC104ZFCP VCTYPU1EF104Z C502 Ceramic 180pF 50V...

Page 30: ...Film 0 068 F 200V 10 CC683KPHP VCQPSC2DA683K C701 A Across Line 0 22 iF 125V AC 20 AC 0091 RC QZ019DCEZZ C702 Ceramic 0 0 VF 250V AC 1 4kV DC 5 CC103JYCP RC KZ007JCEZZ C703 Ceramic 0 0 VF 250V AC 1 4kV DC 5 CC103JYCP RC KZ007JCEZZ C704 Ceramic 0 0 VF 500V 10 CC103KUCP VCKYPB2HB103K C705 A Electrolytic 470 iF 200V 20 CC477MPAP RC EZ0164CEZZ C706 A Electrolytic 330 iF 200V 20 CC337MPAP RC EZ0162CEZZ...

Page 31: ...Z D422 1SS133 Silicon DX2230 RH DX0142CEZZ D481 Zener RD 5 1EB DX0398 RH EX0049CEZZ D491 Zener RD 5 1EB CANADA USA Up to 21987 DX0398 RH EX0049CEZZ 1SS1 19 Silicon USA 21 988 VHD1SS119 1 D492 Zener RD 5 1EB CANADA USA Up to 21987 DX0398 RH EX0049CEZZ 1SS119 Silicon USA 21988 VHD1SS119 1 D493 Zener RD 5 1EB CANADA USA Up to 21987 DX0398 RH EX0049CEZZ 1SS1 19 Silicon USA 21988 VHD1SS119 1 D494 Zener...

Page 32: ... DX0086TAZZ SCR701A Silicon Controlled Rectifier S6192F DX2454 VHSS6192FLB1E FUSES F701 a 4A Fast Blow HF 1193 QFS B4021GEZZ F702 A 1 5A Fast Blow AHF0010 QFS B1521GEZZ ICs IC491 IC SN74S04N HEX Inverter AMX4945 VHISN74S04 1 IC492 IC HD7406 HEX Inverter Open Collector AMX3675 VHIHD7406 1 IC493 IC HD7426 Quad 2 input Gate MX4297 VHIHD7426 M IC494 IC SN74S11N Tripple 3 lnput AND Gate MX6406 VHISN74S...

Page 33: ...E562J R405 10k ohm N0281EEC VRD RA2EE103J R406 Oxide Film 3 9k ohm 1W 5 N0237EGD VRS VV3AB392J R407 1 0k ohm N0281EEC VRD RA2EE103J R408 1 2k ohm N0199EEC VRD RA2EE122J R409 820 ohm N0187EEC VRD RA2EE821J R410 1 20 ohm N0136EEC VRD RA2EE121J R411 Carbon 1 5k ohm 1 8W 5 N0206EBC VRD RA2BE152J R412 Carbon 1 8k ohm 1 8W 5 N0210EBC VRD RA2BE182J R413 Carbon 470 ohm 1 8W 5 N0169EBC VRD RA2BE471J R414 C...

Page 34: ... 5 82 ohm See Controls PCB A Not used Not used Oxide Film 3 3k ohm 1W 5 Oxide Film 2 2k ohm 1W 5 Oxide Film 270 ohm 1W 5 15k ohm 8 2k ohm N0187EBC N0199EEC N0122EEC N0183EBC N0206EBC N0169EEC N0187EBC N0199EEC N0122EEC N0122EJD N0189EEC N0375EEC N0281EEC N0183EEC N0132EEC N0176EBC N0107EEC N0257EEC N0162EEC N0224EBC N0281EEC N0122EGD N0040EFC N0247EBC N0169EEC N0288EBC N0340EBC N0230EEC N0247EEC N...

Page 35: ...ohm 1W 5 N0037EGD VRN VV3AB3R3J R701 A Cement 1 8 ohm 5W 10 N0029FKF VRW KP3HC1R8K R702 180k ohm N0387EEC VRD RA2EE184J R703 AA 33k ohm N0324EEC VRD RA2EE333J R704 a Oxide Film 150 ohm 1 2W 5 N0142EFD VRS SV2HC151J R705 a Oxide Film 330 ohm 3W 5 N0159EJD VRS VV3LB331J R706 AA 82k ohm N0360EEC VRD RA2EE823J R707 See Controls PCB A R708 A Cement 2 7 ohm 5W 10 N0034FKF RR WZ0058CEZZ R709 AA Carbon 3 ...

Page 36: ...607 Pot H Hold B curve 5k ohm AP7419 RVR B4460CEZZ 3707 AA Pot B ADJ B curve 1k ohm P 7681 RVR B4457CEZZ MISCELLANEOUS R701 A Posistor T 1251 RMPTP0026CEZZ Holder Fuse F 1406 QFSHD1002CEZZ REF IMO DESCRIPTION RS PART NO MFR S PART NO P C B Assembly CRT Socket PCB B AX 9204 DUNTK4164RA0H Consists of the following CAPACITORS 3850 Ceramic 150pF 50V db5 CC151KJCP VCCSPA1HL151J 3851 Ceramic 150pF 50V 5...

Page 37: ...ntrols PCB B R857 1 50 ohm N0142EBC VRD RA2BE151J R858 See Controls PCB B R859 820 ohm N0187EBC VRD RA2BE821J R860 820 ohm N0187EBC VRD RA2BE821J R861 820 ohm N0187EBC VRD RA2BE821J R862 See Controls PCB B R863 See Controls PCB B R864 See Controls PCB B R865 A Oxide Film 5 6k ohm 2W 5 N0257EHD VRS VV3DB562J R866 A Oxide Film 5 6k ohm 2W 5 N0257EHD VRS VV3DB562J R867 A Oxide Film 5 6k ohm 2W 5 N025...

Page 38: ...CEZZ REF NO DESCRIPTION RS PART NO MFR S PART NO P C B Assembly LED PCB C Consists of the following AX9205 DUNTK4165RA0H CONNECTOR NA NC Socket for Main PCB 2 pin AJ 4028 CSOCN0230RA03 DIODE D718 GL 9PR24 AL0010 RH PX0161CEZZ MISCELLANEOUS Parts not located on the PCBs A L701 CRT AA DY601AA Cord AC Coil Automatic Degaussing U S A CANADA Magnet Purity and Static Convergence Picture Tube E8093B22 PD...

Page 39: ...Z 103 Screw 5 x 30mm Tapping 1 Hexagon Head LX TZ3042CEFD 104 Screw 3 x 6mm Machine Bind Head U S A Up to 55000 CANADA Up to 7000 XHBSD30P06000 Screw 3 x 8mm Machine Binding Head XHBSD30P08000 U S A 55001 CANADA 7001 105 Knob Control AK0338 JKNBK1168CEKA 106 Bracket AC Cord U S A Up to 21987 55001 LANGK0288CESA USA 21988 55000 LANGK0298CESA CANADA LANGK0276CESA 107 Wire Holder Black LHLDW1033CE00 ...

Page 40: ...e LHLDW1019CEZZ 130 Label Model NO CANADA TLABN0042CEZZ 131 Label Address CANADA TLABZ0107CEZZ 132 Label Fuse Caution CANADA TCAUS3111CEZZ 133 Label Fuse Caution CANADA TCAUS3095CEZZ 134 Label CSA CANADA TLABS0003CEZZ 135 Screw 4 x 8mm Machine Pan Head XBPBW40P08000 136 Spring Washer XWSPW42 10000 137 Nut 4 x 3 2mm XNEBW40 32000 138 Screw 3 x 8mm Tapping 2 Brazier Head XCASD30P08000 139 Wire Holde...

Page 41: ...re pF unless otherwise noted PWiF 4 G indicates 2 tolerance may be used VOLTAGE MEASUREMENT CONDITIONS 1 All DC voltages are measured with SSVM connected between points indicated and chassis ground Line voltage is set at 120V AC and all contols are set for a normal picture unless otherwise indicated 2 All voltages are measured with 1000 V B W or Color signal ...

Page 42: ... in dicated to chassis ground 6 0 Vp p H 225 Vp p H 900 Vp p H 1 5 V p p H D 4 2 Vp p H m 12 Vp p H 7 31 Vp p H 8 3 5 Vp p V fflH 9 4 2 Vp p V 10 1 9 Vp p V il 2 0 Vp p H SEMICONDUCTOR LEAD IDENTIFICATION Q85I Q50I Q86I Q502 0871 Q401 45 1 Q402 Q46I 0421 047 Q422 0601 I 2SC 1826 G 2SC2068 D LB Q40I ZSA 10 1 5 Y Q402 2SA854 Q 0421 1 Q422 0451 2SCI6I5 Y 0461 0471 0601 2SCI2I3A C 51 n J 0701 1 TOP VI...

Page 43: ...ORT WORTH TEXAS 76102 CANADA BARRIE ONTARIO L4M 4W5 TANDY CORPORATION AUSTRALIA BELGIUM U K 91 KURRAJONG AVENUE RUE DES PIEDS D AL0UETTE 39 8ILST0N ROAD WEDNESBURY MOUNT DRUITT N S W 2770 5140 NANINNE NAMUR WEST MIDLANDS WS10 7 JN lOAK Printed in Japan ...

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