Tandy CM-8, Service Manual

Page 1: ...TANDY erv1ce Color Monitor CM 8 for Color Computer 3 Catalog Number 26 3215 CUSTOM MANUFACTURED FOR RADIO SHACK A DIVISION OF TANDY CORPORATION ...

Page 2: ...justment 16 2 Horizontal Hold Adjustment 16 3 Vertical Size Adjustment 16 4 Focusing 16 5 High Voltage Check 17 6 Vertical Linearity Adjustment 17 7 X ra y Protector Circuit Test 17 Colo r Purity Adjustment 17 9 Black and White Tracking 18 0 Static Center Convergence 19 Dynamic Convergence 20 OU BLESHOOTING GUIDE 21 IRI G DIAGRAM AND PARTS LOCATION 25 I TED CIRCUIT BOARDS Top and Bottom Views ain ...

Page 3: ...ite peak 6 Display color All colors 7 High voltage 23 kV Oµ A 27 5 kV max Oµ A 8 Picture linearity a Horizontal 10 max b Vertical 10 max 9 Synchronous pull in range a Horizontal 15 701 kHz 300 H 400 z b Vertical 59 7 Hz 7 Hz 10 Screen pitch 0 52 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 spe...

Page 4: ...e rated value no higher Operation at higher voltages may cause a failure of the picture tube or high volt age circuitry and also under certain conditions may produce radiation in excess of desirable levels 4 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: ...splay 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 voltage wattage etc Replacement parts that have these special safety characteristics are identified in this manual electrical components having such features are identified by a 6 ...

Page 6: ...602 0851 RED OUTPUT FROM PIN OF IC451 R862 R BIAS This pulse is taken from terminal ofT602 and recti fied by D717 and then used as 145V DC The brightness signal from the Blanking transistor 0402 is applied to the emitters of 0851 0861 and 0871 C853 C854 and C855 are peaking capacitors Color signals from the outputs of IC451 are applied to the bases of 0851 0861 and 0871 The picture tube used in th...

Page 7: ... next horizontal drive circuit From Pin of IC601 C609 l 0601 HOR IZ DR IVE The pulse switching mode of the driver and output stage is a reverse polarity type that is when the driver transistor 0601 is ON the output transistor 0602 is OFF 5 Horizontal Output and HV Rectifier Figs 3 5 The horizontal dirve signal developed at pin of the deflection processor integrated circuit IC601 is am plified thro...

Page 8: ...I _ _ 1 4 1 B Figure 4 Equivalent Circuit of Horizontal Output Circuit C625 C628 R714 r 1 i TO CRT SE COND ANODE TO CRT FOCUS 1 TO CRT SCREEN To Blanking To Horizontal AFC DET Circuit 1 V l t 1 To CRT Heater l JV _ 1t __ 18V C715 I_ C510 Figure 5 Horizontal Output and HV Rectifier Circuit 8 ...

Page 9: ...elec tromotive force between those windings irrespective of the magnitude of the collector current resulting in a voltage being induced between the driving w indings and The induced voltage is positively feed back to the base of the output transistor 0702 to in crease the base current of this transistor resulting in a further increase in the collector current The above operation occurs instantaneo...

Page 10: ...NE FILTER 0710 R714 POWER R631 CONVERTER SW701 0701 0704 HORIZ BRIDGE REGULATOR OUTPUT RECTIFIER CIRCUIT XFMR R716 Figure 7 Block Diagram of Power Supply PR701 L701 ADG f m z i Figure 8 ADG Circuit 10 115V 0717 145V 18V 12V R401 5 1V R481 TIME ...

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Page 12: ...1 is determined by R 30 7 Power is supplied to IC301 through pin When current does not flow through pin the volt age at pin is increased Due to the increase in volt age a current flows into 0302 through R310 and D304 0302 is then turned on so that current flows through R308 and the voltage at pin is decreased When current flows through pin of IC301 the volt age applied to pin is decreased If the v...

Page 13: ... on the PCB A and dis connect the connector K Figure 11B Ma in PC 8 P CB A l 13 5 Disconnect the connectors NA and M on the PCB A main PCB 6 Loosen the wire holder fi xing the RGB output lead degaussing lead speaker lead and LED lead Figure 118 7 Remove the PCB A main PCB from the front cabinet 3 Remove screw in the PCB C LED PC B and remove PCB C from the front cabinet Figure 118 Note When servic...

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Page 15: ...te the H character pattern press any key after the screen is white 40 PRINT Press ENTER to begin 50 A INK EY 1F A THEN 50 60 POKE HFF98 4 70 POKE HFF99 H75 80 PALETTE 0 0 90 CLS 1 PALETTE 0 64 100 A INKEY 1F A THEN 100 110 FOR A 1TO1919 120 PRINT H NEXT 130 GOTO 130 140 END Crosshatch pattern 10 REM Crosshatch pattern SH x 12V 20 WIDTH SO PALETTE RGB PALETTE O O PALETTE 8 54 CLS9 30 HSCREEN 2 40 F...

Page 16: ...his is not a problem related to this ad justment Note 2 Clockwise rotation of the B voltage ad justing control will increase the B pow er supply voltage 2 Horizontal Hold Adjustment 1 Operate the computer in such a way that the let ter H covers the entire screen data display peri od 44 698 µ S horizontal 14 331 mS vertical 2 Adjust the horizontal hold control R607 until the picture on the screen b...

Page 17: ...r does not stop in step 4 the circuit must be repaired before the set is returned to the customer 17 8 Color Purity Adjustment The Monitor must have been operating 15 minutes pri or to this procedure and with the faceplate of the CRT at room temperature The Monitor is equipped with an automatic degaussing circuit However if the CRT shadow mask has become excessively magnetized it may be necessary ...

Page 18: ...nd verti cal 14 331 msec 18 5 Turn off the sw itch SW851 6 Adjust the screen control on T602 so that the raster is dimly shining 7 Achieve white balance using the other two bias controls for the shining color for example blue and green when the raster is shining in red 8 Adjust the screen control to obtain the just cut off position 9 Using the computer feed a white signal input in stead of the bla...

Page 19: ...nes Rotate the pair of rings maintaining spacing between tabs to converge the horizon tal red and blue lines Refer to Figure 15 b After completing the red and blue center conver gence locate the pair of six pole magnet rings Rotate the individual rings change spacing be tween tabs to converge the vertical red and blue magenta and green lines Rotate the pair of rings maintaining spacing between tab...

Page 20: ...t tilt ad justment wedges G and 0 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 Q between the deflection yoke and the CRT until the misconvergence illustrated in Figure 18 has been corrected 5 Alternately change the spacing between and depth of insertion of the th...

Page 21: ...e the signal cable is plugged in securely and turn the com puter power on Now input any signal to produce the raster on the screen No Power horizontal sync protector circuit Video output circuit 3 A high voItage is not r C_h_e_c_k_t_h_e vo_l_t_ag_e_ Ie_vi e_l_a_t_t_h_e_c_o_l_I e c to _r_o_f developed 0851 If the voltage is normal the voltage High voltage circuit can be varied between 120 to 140 wi...

Page 22: ...1 Check 0851 and its related circuits 1 0851 1 1 0404 I L _ __ _J Input cable input socket computer IC451 Both horizontal and vertical synchronization cannot be obtained NO HORIZONTAL SYNCHRONIZATION But vertical synchroni zation is normal Does pin Q3 of IC601 have a saw tooth wave and sync signal r I IC601 I R605 I I R606 I 1 R607 I L _J r IC601 L _J With the H hold control adjusted does the hori...

Page 23: ...ote Ripple current signal is represented at the junction of D703 and 0704 Circuits Checked IC451 and its related circuits 0851 and its related circuits 0861 and its related circuits 0871 and its related circuits The raster is colored in red or cyan Check the red video circuit 0851 r 1 I IC451 C850 I I 0851 R865 I I C853 R868 I 1 R856 I R862 L_ _ _ _I NO SPECIFIC COLOR The raster is colored in gree...

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Page 29: ...A 106 Wire Holder Black W 3384 LHLDW1033CEOO 107 Label Model No U S A TLABM1966CEZZ CANADA TLABM2040CEZZ 108 Spring Grounding Strap MSPRT0020CEZZ 109 Wedge Yoke PSPAG0028CEZZ 110 Wire Grounding Strap OEARC1408CEZZ 111 Not used 11 2 Not used 113 Wire Holder White U S A LHLD W1037CEZZ 114 Heatsink IC501 PRDAR5058CEFW 11 5 Screw 3 x 1Omm Machine Pan Head HD 2061 XBPSD30P10KSO 116 Heatsink 0602 PRDAR5...

Page 30: ...Z3090CEFD 133 Wire Holder CANADA LHLDW1005GEZZ 134 Bracket AC Cord HC 4302 LANGK0276CESA 135 Address Label TLABZ0107CEZZ 136 Model Label Internal TLABN0042CEZZ 137 Manufactured Label TLABN0059CEZZ HARDWARE AHW 2603215 DBNW 0001RAOA KIT 138 Screw 4 x 20mm Tapping 1 Brazier Head AHD 6002 XTASD40P20000 139 Screw 4 x 12mm Tapping 1 Brazier Head HD 1671 XTASD40P12000 34 ...

Page 31: ...sed Ceramic 1OOpF 500V 10 I Not used C450 C451 C452 C453 C454 C455 C456 C457 C458 C459 C460 C461 Electrolytic 2 2µF 50V 20 Electrolytic 33µF 16V 20 Electrolytic 0 15µF 50V 50 15 Electrolytic 0 15µF 50V 50 15 Electrolytic 0 15µF 50V 50 15 Electrolytic 0 15µF 50V 50 15 Electrolytic 1µF 50V 20 Electrolytic 0 15µF 50V 50 15 Electrolytic 0 15µF 50V 50 15 Ceramic 0 1µF 25V 80 20 I Not used C480 RS PART ...

Page 32: ... CC 1 03KUBC VCKYPB2HB103K C516 Ceramic 120pF 50V 5 CC 121JJBC VCCSPA1HL121J C517 I Not used C600 C601 Mylar 0 01 8µF 50V 10 CC 183JJBM VCOYSH1HM183K C602 Not used C603 Electrolytic 1µF 50V 20 CC 105MJBA VCEAAA1H W105M C604 Polypro Film 0 0027µF 1OOV 2 CC 272GUBH VCOPSA2AA272G C605 Mylar 0 0068µF 50V 10 CC 682KJBM VCOYSH1HM682K C606 Mylar 0 0022µF 50V 5 CC 222JJBM VCOYSH1HM2 22J C607 Electrolytic ...

Page 33: ... 1 µ F 50V 10 CC 104KJBM V C OYSH1HM104K C710 Polypro Film 0 01 µF 630V 10 CC 103KVCH VCOPSB2JA103K c711 Electrolytic 330 tF 160V 20 CC 33 7MNCA RC EZ0070CEZZ C712 Ceramic 0 0033µF 125V AC 20 CC 332MXCC RC KZ0030CEZZ C713 Electrolytic 1OOµF 160V 20 CC 107MNCA VCEAAH2C W 107M C714 Electrolytic Nonpolarized 1OµF 50V 20 CC 106MJBA VCE9AA1HW106M C715 Electrolytic 470µF 50V 20 CC 477MJBA VCEAGA1HW477M ...

Page 34: ...049CEZZ D493 Zener RD5 1EB Silicon DX 0398 RH EX0049CEZZ D494 I Not used D500 D501 Zener RD6 2F Silicon DX 2553 RH EX0247CEZZ D502 S5277G Silicon DX 2276 RH DX011 OCEZZ D503 Not used D504 TVR1J Silicon DX 2617 RH DX0105TAZZ D505 I Not used D600 D601 1SS133 Silicon DX 2230 RH DX0142CEZZ D602 Not used D603 RH 1S Silicon DX 2275 RH DX0086TAZZ D604 Zener RD 12E Silicon DX 2306 RH EX0047CEZZ D605 Zener...

Page 35: ...480 IC481 IC HD74LS 136P Sync EX OR Bipolar Digital IC482 I Not used IC500 IC501 IC LPC 1378H Voltage Booster Blanking Pulser Vertical Output Bipolar Linear IC502 I Not used IC600 IC601 IC HA11235 SYNC AFC X RAY Protector Horizontal OSC Vertical OSC Driver Bipolar Linear COILS L601 Peaking Coil L602 Linearity Coil L603 I Not used L701 39 RS PART NO DX 2446 DX 0856 DX 2275 DX 2558 HF 1193 AHF 1302 ...

Page 36: ...5Y 1 E VS2SA854 Q 1 E VS2SC2482 I 1 VS2SD1426 I 1 E VS2SA1015Y 1 E VS2SC2555 I 1 RESISTORS Unless otherwise specified resistors are 1 4W 5 carbon type R301 Metal Film 1 5 ohm 2W 5 R302 1OOK ohm 1 8W 5 R303 68K ohm R304 2 2K ohm R305 Not used R306 33K ohm 1 8W 5 R307 390 ohm R308 Oxide Film 82 ohm 3W 5 R309 47K ohm R3 10 100 ohm R3 11 6 Oxide Film 47 ohm 3W 5 R312 270K ohm R3 13 1K ohm R3 14 See Co...

Page 37: ...ohm 1K ohm 2 7K ohm S 2K ohm Oxide Film 6S ohm 1W 5 See Controls PCB A 6 S ohm 1 2W 5 41 RS PART NO N 02SSEEC N 0257EEC N 02S1 EFC N 0237EGD N 02S 1EFC N 01 S7EEC N 0136EEC N 0206EBC N 0169EBC N 0116EBC N 0116EBC N 0116EBC N 0224EEC N 0206EEC N 0247EEC N 0262EEC N 021 OEEC N 02SSEBC N 0311 EBC N 0132EEC N 0247EEC N 0136EJD N 0159EBC N 01 S7EBC N 0237EEC N 0257EEC N 0196EEC N 0224EEC N 02 71EEC N 0...

Page 38: ...VRD RA2EES22J R605 33K ohm N 0324EEC VRD RA2EE333J R606 12K ohm N 02SSEEC VRD RA2EE 123J R607 See Controls PCB A R60S 6SOK ohm N 0433EEC VRD RA2EE6S4J R609 220 ohm N 0149EEC VRD RA2EE221J R610 1 SK ohm VRD RA2EE 1 S2J R611 2 2K ohm VRD RA2EE222J R612 Not used R613 Oxide Film 1 2K ohm 3W 5 N 0199EJD VRS VV3LB122J R614 Oxide Film 4 7K ohm 1W 5 N 0247EGD VRS VV3AB472J R615 Carbon 47 ohm 1 2W 5 N 0099...

Page 39: ...T601 Horizontal Driver T602 Flyback T603 I Not used T700 T701 Power Converter SWITCH SW701 Power I 43 RS PART NO N 0067EFC N 0063EFD N 0037EGD N 0029FKF N 0237EEC N 0271EEC N 0187EEC N 021 OEEC N 0271 EEC N 0022EHD N 0082EHD N 0067EEC N 0107FKF N 0387EFC N 0522EFD N 0034EKF N 0460FFB N 0015GED N 0159EBC N 0067EJD N 0111 EHD N 0206EEC N 0199EEC ATB 0495 ATA 0026 AS 0015 MFR S PART NO VRD RA2HD120J ...

Page 40: ...P 2009 RV R B5264CEZZ R703 Pot B ADJ B Taper 1K ohm P 2011 RVR B5261CEZZ MISCELLANEOUS PR701 Posistor T 1251 RMPTP0026CEZZ Holder Fuse F 1406 OFSHD100 2C EZZ TP451 Test Point QLUPG0109CEF W REF NO DESCRIPTION RS PART NO MFR S PART NO P C B Assembly CRT Socket PCB Bl AX 0134 DUNTK4749RAOH Consists of the following CAPACITORS C850 Ceramic 150pF 50V 5 VCCSPA1HL151J C851 Ceramic 150pF 50V 5 VCCSPA1HL1...

Page 41: ...lid 2 7K ohm 112 10 R869 Solid 2 7K ohm 112W 10 R870 Solid 2 7K ohm 1 2 10 R871 220K ohm R872 Solid 470K ohm 112W 10 SWITCH SW851 Luminance Video Cut off CONTROLS R856 R858 R862 R863 R864 Pot Red Drive B Taper 500 ohm Blue Drive B Taper 500 ohm Pot Red Bias B Taper 5K ohm Pot Green Bias B Taper 5K ohm Pot Blue Bias B Taper 5K ohm 45 RS PART NO MFR S PART NO VS2SC2068LB1E VS2SC2068LB1E VS2SC2068LB1...

Page 42: ...LED RH PX0161CEZZ MISCELLANEOUS Parts not located on the PCBs 6 Cord AC AW 3354 OACCD5008CEZZ L701 6 Coil Automatic Degaussing ACA 9017 RCI LG0267CEZZ Magnet Purity and Static Convergence HC 3479 PMAGF3006CEZZ CRT 6 L Picture Tube E8137822 DT MW AXX 8022 VBE8137822 1Y DY601 6 Yoke Deflection HTB 0436 RCI LH 1535CEZZ Signal Input Cable Unit U S A AW 3355 QC NW 0699CEZZ CANADA QCN W 0736CEZZ 46 ...

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Page 44: ...In the chart w aveforms are measured from the point in dicated to chassis ground SEMICONDUCTOR LEAD IDENTIFICATION 85 1 86 1 0602 I O J 1 l B 2501426 2SC2 068 LB J 0 70 2 B 2 SC2555 3 4 0 2 3 2 0 1 0 1 0 l 2S C l 8 15 l l 2SC2 02 25 I 15 l 2SA8 4 l J 2 SC 2482 2SA I 15 I l SCR70 I l G s 3042 50 I TOP VI EW I I I I I I IC 48 1 H074 L S l 36P 0 D 0 C 6 0 1 A ll 235 r i I I 1 I IC 5 01 µPC l 378 H I ...

Page 45: ...11A6 RADIO SHACK A Division of Tandy Corporation Fort Worth Texas 76102 Pr int ed in Japan ...