Dumont 180, Service Manual

Page 1: ......

Page 2: ...ch we believe you will find easy to install and service in spite of the apparent complexity of the subject Television TECHNICAL INFORMATION Frequency Ranges Four Television Channels provided present alignment as follows AUDIO VIDEO STEP STATION SIDEBAND CARRIER CARRIER A NBC Single 49 75 45 25 B CBS Single 55 75 51 25 C D NBC Double 49 75 46 5 Power Ratings Power supply 110 to 120 volts 50 to 60 c...

Page 3: ...e schematic drawings have been provided which due to their size will be found more readable than a single drawing CAUTION AND WARNING The set is equipped with a safety switch which automatically opens upon the removal of the back of the cabinet This protects the operator from dangerous high voltages which would otherwise be exposed The serviceman that is engaged installing or servicing television ...

Page 4: ......

Page 5: ......

Page 6: ...o specific form can he advised and we can merely suggest that you start by using horizontal polarization and change if necessary to produce the best results Location of the Antenna Whenever possible the Dipole should be erected so that it is in line of sight with the transmitter This does not mean that no signals can be secured where a direct view of the transmitter cannot be obtained Surprising r...

Page 7: ......

Page 8: ...ontrol is necessary to properly tune both the sight and sound channels Simply adjust this control until the best reception of the sound is secured and at this point the picture signal will be correctly tuned 4 Marked INTENSITY The intensity or brightness of the picture is controlled by this knob It should be adjusted in conjunction with Control No 1 to get the best picture Note it is a good plan t...

Page 9: ......

Page 10: ...is at D C ground potential As the cathode approaches ground potential due to the discharge of C75 the 6AD5G triode becomes conducting As plate current flows C76 is discharged producing the return trace of the sawtooth The surge of plate current through the winding of the oscillation transformer induces a voltage in the grid winding of proper polarity to drive the grid more positive thereby reducin...

Page 11: ...ning circuits 4 Defective cathode ray tube No modulation 1 Defective or shorted antenna 2 Defect in video receiver 3 Too much bias on modulator electrode 4 Defective cathode ray tube Poor focus 1 Improper voltages supplied cathode ray tube check entire divider circuit 2 Defective video receiver 3 Poor adjustments 4 Defective cathode ray tube Uneven brilliance 1 Hum from power source 2 Defective sc...

Page 12: ...igh resistance values see the component parts list A good voltmeter is also of value and it too should have a high range The Weston Model 722 can be used thus combining both of the above instruments This meter is now equipped with safety prods good insulation is a necessity where high voltages are checked Sensitivity of 20 000 ohms per volt is provided along with a range of 5 000 volts which adds ...

Page 13: ...mately 10 volts peak to peak at an impedance of 5 000 ohms Some of its many uses are as follow 1 Testing overall frequency and phase response of a television receiver 2 Testing ghost response 3 Measuring resolution of cathode ray tubes 4 Adjustment of linearity of horizontal sweep 5 Production of interlaced synchronization for testing interlace and rasters Useful for controlling the Type 202 Telev...

Page 14: ......

Page 15: ......

Page 16: ......

Page 17: ......

Page 18: ......

Page 19: ...00 pot 2 20 2 2 pot pot 1 1 1 2 pot pot pot pot 2 2 pot 2 pot 10 1 1 2 2 pot pot R R W R S W S S S R W R R R R S S R R R R R R R R R R R S S R R R W R R R S R R S R R R R R 200 201 202 203 204 205 206 207 208 209 210 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 245 246 257 258 500 000 2 000 150 5 000 400 3 000 3 000 3 000 3...

Page 20: ...50 450 450 1500 1500 4000 4000 4000 4000 400 400 50 1500 trimmer trimmer trimmer trimmer variable 400 400 400 400 trimmer 400 400 400 400 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 256 257 258 259 260 265 01 01 001 3 30 3 30 3 30 3 30 3 30 3 30 3 30 3 30 L53 L53 L53A L53A T 20 T...

Page 21: ...ction of the receiver AMPLITUDE A term synonymous with gain or size AXIS In television the horizontal plane is called the X Axis and the vertical the Y Axis CATHODE RAY TUBE An evacuated glass tube comprised of a structure for producing and focusing a stream of electrons upon an internal screen COAXIAL CABLE OR LINE A special cable for conveying television signals with as little loss as possible C...

Page 22: ...he technique of dividing the frame into two fields with displaced lines to eliminate flicker INTERACTION A term usually used by designers indicating leakage or the mixing of a signal into another circuit LINE A single line of the 441 comprising the television picture LINEARITY Means uniform rate of motion This is required as the picture will be distorted in non linear portions MODULATION A process...

Page 23: ......

Page 24: ......