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Radio Shack TRS-80 Service Manual Download Page 44

RADIO SHACK, A DIVISION OF TANDY CORPORATION

U.S.A.: FORT WORTH, TEXAS 76102

CANADA: BARRIE. ONTARIO L4M 4W5

TANDY CORPORATION

6A3 

Printed in U.S.A.

AUSTRALIA

BELGIUM

U. K.

91 KURRAJONG ROAD

PARC INDUSTRIEL DE NANINNE

BILSTON ROAD WEONESBURY

MOUNT ORUITT, N.S.W. 2770

5140 NANINNE

WEST MIDLANDS WS10 7JN

Summary of Contents for TRS-80

Page 1: ...TRS 80 MICRO COLOR COMPUTER MODEL MC 10 Catalog Number 26 3011 CUSTOM MANUFACTURED FOR RADIO SHACK A DIVISION OF TANDY CORPORATION 26 3011...

Page 2: ...TV Switch Box 16 Power Supply 17 VDG 17 Device Selection 19 System Timing 19 RAM 20 Modulator 20 V TROUBLESHOOTING 21 VI PARTS LIST 25 VII PRINTED CIRCUIT BOARDS 30 VIII IC INTERNAL CONNECTIONS 33 IX...

Page 3: ...3 SECTION I SYSTEM DESCRIPTION...

Page 4: ...cessor clock E The CPU will be granted access to the RAM upon request only during the high state of E This allows efficient usage of the RAM with no waiting by the CPU and no visible conflict on the d...

Page 5: ...5 SYSTEM BLOCK DIAGRAM...

Page 6: ...0F Port 3 Control and Status Register 000E Input Capture Register low byte 000D Input Capture Register high byte 000C Output Compare Register low byte 000B Output Compare Register high byte 000A Count...

Page 7: ...7 SECTION II SPECIFICATIONS...

Page 8: ...it 6803 8 bit processor clock speed 0 89 MHz Memory Size ROM for BASIC 8K RAM 4K expandable up to 20K external Video Display Character display 512 32 x 16 upper case characters Semi Graphic display 64...

Page 9: ...9 SECTION III DISASSEMBLY REASSEMBLY...

Page 10: ...op shield is soldered to the PC Board Remove this solder with solder wick or a desolder ing tool Bend the protruding edge of the shield upward until it is parallel to the slot and remove top shield RE...

Page 11: ...11 SECTION IV THEORY OF OPERATION...

Page 12: ...CIRCUIT The reset circuit is composed of switch S1 diode D9 resistor R24 capacitor C8 and two gates of IC U12 R24 and C8 form a simple time constant so that during power up or whenever the reset switc...

Page 13: ...OUTPUT INPUT TO TAPE OUTPUT FROM TAPE INPUT TO THE PIA DATA STORED IN MEMORY 4 6v 0v 1v 0v 2 5v 0v 2 5v 5v 0v The End of File block is a standard block with a length of 0 and the block type equal to...

Page 14: ...e TTL input switches states A 100 ohm resistor R1 is included to provide a cur rent limit on the output The two input signals RS232lN and CD utilize identical circuits and share a common bias resistor...

Page 15: ...9 CPU Address Bit 9 22 A10 CPU Address Bit 10 23 A11 CPU Address Bit 11 24 A12 CPU Address Bit 12 25 A13 CPU Address Bit 13 26 A14 CPU Address Bit 14 27 A15 CPU Address Bit 15 28 E Main CPU Clock 0 89...

Page 16: ...puter the signal is connected to a balun in the switch box which matches the modulator s 75 ohm output impedance to a TV s 300 ohm antenna input impedance This signal is then connected to the switch T...

Page 17: ...of the op amp VDG The video interface function in the MC 10 is performed by the MC6847 This is a flexible video display generator that will produce nine colors eight colors and black an alphanu meric...

Page 18: ...ck 64 Display elements in columns 32 Display elements in rows Black x x Lx C2 C1 C0 Color 0 x x x Black 1 0 0 0 Green 1 0 0 1 Yellow 1 0 1 0 Blue 1 0 1 1 Red 1 1 0 0 Buff 1 1 0 1 Cyan 1 1 1 0 Magenta...

Page 19: ...t used externally to the CPU The next 16K segment is used for system RAM The third 16K segment is used to read the keyboard and to write to the VDG control register The final 16K is reserved for syste...

Page 20: ...U is writing to RAM MODULATOR The outputs from the MC6847 are connected directly to the modulator The modulator unit is built around the MC1372 This is a linear inte grated circuit which is designed t...

Page 21: ...21 SECTION V TROUBLESHOOTING...

Page 22: ...g then the most likely problems are a memory or buffer chip failure or a short on the address or data bus In this case you will have to methodically check the address and data lines while looking for...

Page 23: ...lt supply voltage is the output of the regu lator With the power pack unplugged measure the resistance between the 5 output and ground If this shows zero resistance the prob lem is a short to ground I...

Page 24: ...1 Set switch to CH 4 2 Adjust T102 core so that frequency counter of spectrum analyzer shows 67 65 MHz 3 Set switch to CH 3 4 Adjust trimmer capacitor of C113 so that frequency counter of spectrum ana...

Page 25: ...25 SECTION VI PARTS LIST...

Page 26: ...022 16 30 Axial Ceramic C24 26 0 022 50 80 20 Radial Ceramic C27 0 1 25 20 Radial Ceramic C28 0 022 50 80 20 Radial Ceramic C29 0 022 16 30 Axial Ceramic C30 32 0 022 50 80 20 Radial Ceramic C33 150P...

Page 27: ...R20 10K x 8 1 4 5 Resistor Array R21 4 7K 1 4 5 Carbon R22 23 4 7K 1 6 5 Carbon R24 100K 1 4 5 Carbon R25 4 7K 1 4 5 Carbon R26 100K 1 4 5 Carbon Ref No Description R S Part No Mfr s Part No S1 RESET...

Page 28: ...S32N or OR GATE MB74LS32M or HD74LS32P MOTOROLA FUJITSU HITACHI U14 MC14503BCP or BUFFER HD14503BP or PD4503BC or MSM4503RS MOTOROLA HITACHI NEC OKI U15 LM339N or COMPARATOR PC339C MOTOROLA NEC U16 MC...

Page 29: ...Modulator MDV 1 Custom 525010030A 9 Connector Flat Wire 193903430A 10 Sheet Shield 473310380A 11 Knob Channel Black 659510320A 12 Cabinet Bottom 601310290A 13 Foot Rubber 608010080A F1 Screw Top Tite...

Page 30: ...30 SECTION VII PRINTED CIRCUIT BOARDS...

Page 31: ...31 MAIN P C B TOP VIEW...

Page 32: ...32 BOTTOM VIEW...

Page 33: ...33 SECTION VIII IC INTERNAL CONNECTIONS...

Page 34: ...34 IC INTERNAL CONNECTIONS U1 MC6803G Motorola or HD6803P Hitachi...

Page 35: ...35 U11 MC6847P Motorola...

Page 36: ...36 U2 SN74LS373N Motorola or MB74LS373M Fujitsu U7 SN74LS245N Motorola or MB74LS245M Fujitsu...

Page 37: ...37 U3 MB8364M Fujitsu U9 10 PD4016C 1 NEC or PD4016D 1 NEC or MB8128 15P Fujitsu or MSM2128 20RS Oki...

Page 38: ...38 U4 SN74LS155N Motorola or MB74LS155M Fujitsu or HD74LS155P Hitachi U5 6 SN74LS367AN Motorola or MB74LS367AM Fujitsu or HD74LS367AP Hitachi...

Page 39: ...N74LS174N Motorola or MB74LS174M Fujitsu or HD74LS174P Hitachi U14 MC14503BCP Motorola or HD14503BP Hitachi or PD4503BC NEC or MSM4503RS Oki U19 SN74LS76AN Motorola or MB74LS76AM Fujitsu or HD74LS76P...

Page 40: ...40 U12 SN74LS14N Motorola or MB74LS14M Fujitsu or HD74LS14P Hitachi U13 SN74LS32N Motorola or MB74LS32M Fujitsu or HD74LS32P Hitachi U20 SN74LS32N Motorola or MB74LS32M Fujitsu or HD74LS32P Hitachi...

Page 41: ...41 U15 LM339N Motorola or PC339C NEC U18 SN74LS74AN Motorola or MB74LS74AM Fujitsu or HD74LS74AP Hitachi...

Page 42: ...42 U16 MC1741CP1 Motorola or HA17741PS Hitachi U17 MC7805CT Motorola or NJM7805A JRC or PC7805H NEC...

Page 43: ...43 SECTION IX SCHEMATlC DlAGRAM SECTION X EXPLODED VlEW...

Page 44: ...S A FORT WORTH TEXAS 76102 CANADA BARRIE ONTARIO L4M 4W5 TANDY CORPORATION 6A3 Printed in U S A AUSTRALIA BELGIUM U K 91 KURRAJONG ROAD PARC INDUSTRIEL DE NANINNE BILSTON ROAD WEONESBURY MOUNT ORUITT...

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