CA Chassis Safety Guidelines HIGH VOLTAGE AND X-RADIATION PROTECTION A potential source of x-rays is the picture tube, if the high voltage (HV) is out of specification. When the HV is operating properly, there is no x-radiation. For the CA chassis family, the HV has no adjustments. A HV shutdown circuit is used to prevent excessive HV and x-ray emissions. SAFETY CIRCUIT TEST PROCEDURE Equipment required: a) Video Generator. b) HV DC meter (0 to 40 KV, high Z).
Preface This manual has been designed as a supplement to the CM-151 CA/CB training manual (923-3351TRM). It provides circuit descriptions as well as troubleshooting flowcharts for both CA and CB chassis. Each description includes schematic diagrams of the particular section(s) being discussed. These inclusions represent a change from some recent training manuals. Moreover, this manual is divided into two distinct sections, respectively, for CA and CB chassis.
Table of Contents Section 1 General Safety Guidelines CA Chassis Safety Guidelines Preface This Table of Contents CA Circuit Descriptions Power Supply Microprocessor Control IF Receiver Video Processing Deflection Control Audio Development CA Troubleshooting Section 2 CB Chassis Safety Guidelines CB Circuit Descriptions Power Supply Microprocessor Control IF Receiver A/V Switching Video Processing Deflection Control Audio Development CB Troubleshooting ...................................................
Power Supply Introduction The CA chassis is a cold ground chassis deriving its power from a switch-mode, flyback type, power supply. It features indirect B+ regulation, over-current protection (OCP), software controlled degaussing, necessities for Energy Star compliance, and provision for future universal power input (85VAC - 265VAC). The switch-mode power supply, or SMPS, converts AC line power to the various DC voltages required by the receiver.
CA CIRCUIT DESCRIPTIONS CX3415 RX3405 B+ VDC CX3408 B+ VDC RX3410 PROV C3414 PROV RX3411 PROV DX3409 PROV CX3409 CX3411 RX3404 RX3407 ICX3400 RX3408 LX3410 DX3406 5 4 3 2 1 B+ VDC QX3401 RX3406 DX3407 TX3401 CX3416 CX3410 18 8 11 To +18 VSB 7 13 RX3403 CX3413 CX3412 15 DX3408 RX3409 16 5 1 To Regulated B+ 4 C3418 <> Another winding from the chopper (pins 13 and 16) provides feedback to the regulation loop in ICX3400.
Power Supply voltage at the base of QX3401 will switch that transistor on, shunting the regulator ICs base drive to ground. Such an action kills the regulators oscillation, thereby eliminating power generation. Several capacitors, CX3408, CX3409, CX3410, and CX3412, are used in the SMPS to reduce EMI (electro-magnetic interference). Additionally, RX3405 and CX3415 serve as a snubber circuit, to reduce peak voltage on the collector (pin 3) of ICX3400s switching transistor.
CA CIRCUIT DESCRIPTIONS ICX3402 regulates from the +18 VSB to provide +5 VSB. The +5 VSB powers the microprocessor, IC6000, and the tuner, TU6000. Additionally, part of the power from the +18 VSB supplies +18 volts to the audio circuitry (+18 AUD). The remainder of the +18VSB power is used when the set is powered up. This powered up voltage is typically referred to as a switched voltage (VSW). The +18 VSW powers the horizontal drive amplifier.
Microprocessor Control Introduction The CA chassis employs IC6000 as its microcontroller. All end user and servicer controls are accessed using this IC. While most of its functions will be described in terms of how they are used by other devices in the receiver, a number of facts concerning the microprocessor and its input devices will now be presented. The microprocessors job is to communicate control instructions and feedback information to and from various other processors and input devices in the set.
CA CIRCUIT DESCRIPTIONS For those CA chassis that have the keyboard and IR detector built onto the module, the schematics are included. Keep in mind, however, that many of the various CA chassis have a keyboard and IR module that is separate from the main board. Microcontroller VCC is provided to pin 27 of the microprocessor from the +5VSBF supply. While this voltage is relatively low, IC6000 is fairly demanding in terms of current. This same voltage also powers the keyboard and IR detector.
Microprocessor Control types of on-screen display (OSD). Neither sync pulses come directly from the video processor where they are first produced. Horizontal sync is actually fed back from the sweep transformer on the flyback pulse line. Vertical ramp signals feed the base of Q6002. Sync is produced on the collector and fed to the vertical amplifier and through R6006M to the V-Sync pin of the micro. OSD or CC (closed captions) are sent as processed RGB (red, green, & blue) from pins 50, 51, and 52.
CA CIRCUIT DESCRIPTIONS Memory The EEPROM, IC6001, is a small but vital part of the CA receiver. This 512 byte memory chip is responsible for storing servicer adjustments, channel information, and user settings, even when power is removed from the set. This information is transferred on the clock and data lines from the micro into pins 5 and 6. The EEPROM is powered by the +5VSBF source at pin 8.
IF Receiver Tuner Cable or off-air signals are received into the television by way of the antenna jack of the tuner, TU6000. The input and output impedance of this device is 75 ohms. It provides for 181 channels (including cable). It uses +33V for tuning, +5VTune as tuner B+, +4.3V for AGC, and on some chassis +9VSW. As with standard varactor tuners, varying voltage across an internal varactor results in a different internal resonant frequency, whereby tuning of the various channels is achieved.
CA CIRCUIT DESCRIPTIONS IF Composite Audio AGC Pin 1, TU6000 +9VPIF R1202M +9VSW +9VPIF R1225 R1200M R1206M L1200 C1200M +9VSIF L1203 R1201M C1201M L1202 C1218M C1215M C1216 3 L1204 2 C1202M L1201 1 R1209M R1204M C1204M U1200 1 Q1202 R1210M TP1201 R1215M 4 R1220M C1213M Q1200 R1205M 2 5 ICX2200 1 NC R1207M R1203M +9VSW TP1200 R1208M C1203M C1208M R1212M R1211M C1212 C1209M C1210 +9VSW 3 RF-AGC DE-EMPH 54 6 PIFGND R1231M C1207 EXT-AUD 55 5 AGC-FIL R1213M
Video Processing Introduction ICX2200 has numerous duties involved in television image and sound production. As mentioned above, it processes sound and video IF. Additionally, it prepares NTSC video utilizing separated chroma, luma, and OSD from IC6000. Accounting for controlled preference information from the micro such as brightness, tint, sharpness, contrast, etc... the Jungle chip then produces this video signal as RGB which is amplified and sent to the picture tube.
CA CIRCUIT DESCRIPTIONS switching channel of this IC switches the PiP between external and internal video sources based on the PiP Switch1 signal (pin 4, IC2902) from the microprocessor. The internal video signal, denoted TVIN, is the same signal as the one entering pin 37 of ICX2200. Whichever signal is selected is sent as VIN PiP to the PiP module through pin 10 of the PIPA1 connector. The second switching channel of IC2902 allows selection between composite video input and S-Video input.
Video Processing RGB output, this circuit helps to prevent blooming. Excessive current draw in the picture tube will lower voltage and hence decrease beam acceleration. This results in an increase of the sweep. Without ABL, the blooming effect is usually seen when very bright images appear on the screen. ABL should prevent this and extend the life of the picture tube.
CA CIRCUIT DESCRIPTIONS the PIPB1 connector provide sync to the PiP processor. Pins 9 and 10 of the same connector allow I2C bus communication between the PiP board and the microprocessor. PiP brightness however is controlled from pin 11 of the microprocessor. This controls the bias of Q2210, which varies a DC level on the OSD input lines to ICX2200.
Video Processing powered by the +215V source derived from the sweep transformer, but the actual DC voltage at the collectors will be lower (+130 volts is a good ballpark figure) because of the resistors RX5104, 5111, and 5122 and variations in the drive signal.
CA CIRCUIT DESCRIPTIONS Deflection Processing The last portion of the video processor to be discussed is the deflection section. This is the part of the IC from which the vertical and horizontal deflection signals are derived. A critical power supply to this section is the +9VSW which feeds pin 26. Pin 24 emits the V-Ramp signal, from which both vertical sync for the microprocessor and vertical drive for the vertical amplifier are developed. Refer to Q6002 in the microprocessor circuit for this process.
Deflection Control Introduction After deflection control signals are produced by ICX2200, they need to be modified and amplified before they are output to the deflection yoke. The CA chassis accomplishes this necessity for 25 to 36 television sets through the sweep transformer and the surrounding horizontal and vertical deflection circuitry.
CA CIRCUIT DESCRIPTIONS A number of secondary voltages are also provided by the sweep transformers action. Particularly, +215 volts is supplied from pin 2 to the Video Output circuitry for driving color. In addition, +35V and +25V are supplied, respectively from pins 6 and 9, for horizontal width and pincushion control circuitry (when necessary) and for vertical amplification circuitry. Filament voltage is also supplied from pin 7 into pin 1 of connector 2F5.
Deflection Control voltage. The HV shutdown circuit utilizes a rectified DC voltage across CX3003. This voltage is applied to a zener diode, ZDX3004, through a voltage divider consisting of RX3013, RX3015, RX3016, and RX3022. The actual value of the zener will vary according to screen size. When this DC voltage becomes high enough, the zener begins to conduct. The resulting voltage can be metered at pin 29 of ICX2200. If the voltage in the shutdown pin is above +3.
CA CIRCUIT DESCRIPTIONS resulting waveform for yoke current is a sawtooth with rounded peaks. Vertical Amplification Most of the vertical signal amplification is performed by the vertical amplifier, IC2100. This IC contains a power amplifier, a ramp generator, and a flyback generator and is supplied by +25 volts to pin 10. The initial vertical drive signal which should run at 60 Hz is developed from ICX2200, the video processor. Pin 24 of ICX2200 is the vertical ramp (VRamp) source.
Deflection Control CRT Protection CRT protection is provided for the CA in circuitry off the vertical amplifier. In case of a damaged IC2100 or a shorted CX2107 for example, this circuit will prevent damage to the CRT by shutting the microprocessor off. In turn, this action shuts down the television receiver. The circuit is composed of C2109, DX2102, DX2103, R2120M, R2121, R2122M & R2123. Pin 11, the pump-up, of IC2100 emits a pulsing waveform. DX2102 rectifies this waveform to a DC voltage across C2109.
CA CIRCUIT DESCRIPTIONS Audio Amplification There are three audio circuit configurations used in the various CA chassis: mono, stereo, or MTS (Multichannel Television Stereo). While few CA receivers are monophonic sets, the mono audio circuit bears mentioning due to the fact that it is used in each of the three circuit variations. IC804, the audio amplifier IC and heart of the mono audio circuit, is capable of both mono and stereo audio amplification.
Audio Development In the mono circuit, composite audio is fed directly from pin 2 of ICX2200 into the audio amplifier circuit. However, on stereo and MTS models, composite audio is fed into IC1400A or IC1400 respectively. Here the composite sound can be separated into left and right audio channels. Stereo Processing In stereo receivers, IC1400A receives composite audio through C1436 into pin 11.
CA CIRCUIT DESCRIPTIONS +18AUD Audio Output R to IC804 L R1417 ZD1405 C1439 4 5 3 6 2 7 1 8 C1437 C1423 IC1402 C1429 +9VSW * For Stereo Chassis excluding 9-2064, 2065 C1455 12 11 C1409 10 J1406M * R1418M Left & Right Stereo Audio (Pins 1,2, IC1400A) CH-2 9 +5VSBF 8 C1410 7 J1407M * 6 C1456 5 CH-1 4 D1401 Volume Control Pin 46, IC6000 3 2 R1412 1 R1420M R1413 C1438 R1419M IC1401 R1418 Provisional on 9-2064, 2065 External Audio from Jack Pack Audio Switch Pin 44,
Audio Development MTS Processing For MTS chassis, IC1400 serves as the sound processor. It features mono, stereo, or SAP settings. It also features adjustable bass and treble levels, balance adjustment, sound-right audio limiting, front surround sound, and speaker cut-off. Furthermore, whereas internal and external source switching is accomplished by a separate switching IC for the stereo sets, the MTS is capable of internally switching between various sources.
CA CIRCUIT DESCRIPTIONS External Audio Output The output pins here also feed the variable audio output circuitry. This common emitter amplifier has a gain of 12 dB. Q1402 and Q1403 are used to amplify left and right channels respectively. Power for this amplification stage is provided by Q1401, which uses the +15VSW. To reduce popping on the monitors, the switching of Q1401 is briefly delayed by an RC network formed by R1440M and C1440.
Flowcharts Start 1. No Power Is AC connected? No Plug receiver into AC source. Yes Does FX3401 conduct? Replace FX3401. No Yes Is B+ present at CX3420? No Yes Replace FX3402. No Is pin 3, ICX3400 switching? Does FX3402 conduct? Yes Yes Is +18VSB present across CX3424? No No Is QX3401 shorted? Yes Replace TX3401. Replace ICX3400, QX3401, DX3406, DX3407, DX3408. Yes Is +5VSB present across C3426? No Replace ICX3402.
CA TROUBLESHOOTING 2. Shutdown Start Does the set power up for more than 2 seconds? No Yes No Does the DC level at pin 29, ICX2200 rise above 3.5 volts? Yes Check HVshutdown circuit, sweep transformer. Does the set shutdown after just 3 seconds? Yes Check IC2100 & CRT protection circuit. Is B+ running at a constant DC level? Yes CA-28 No Replace ICX3400 No Check microprocessor ciruitry.
Flowcharts 3. No Tuning Start Are all tuner voltages present? (Refer to schematics.) No Check tuner power supplies. Yes Is IF present at pin 11, TU6000? No Does changing the tuner fix the problem? No Check clock and data lines. Replace IC6000 if clock & data lines OK. Yes Is IF present at pins 7, 8, ICX2200? No Check IF line. Replace Q1200, U1200 if necessary. Yes Is IF present at pin 47, ICX2200? No Replace ICX2200.
CA TROUBLESHOOTING 4. No Video Start Is raster present on the screen? No Yes Check Q1201, Q1202 No Is there video at pin 37, ICX2200? Is 1.07 kVp-p signal present on collector of HOT? No Is regulated B+ present across CX3420? Yes Yes Check TX3204. Check HOT and H-drive circuit. No Check power supply. Yes Is composite video present on pin 41, ICX2200? No Replace ICX2200. No Check Q2206 and/or DL2200. Yes Is 0.
Flowcharts 5. No Audio Start Is +18AUD voltage present on pin 9, IC804? No Check audio power supply. Yes Does Q800 test OK? No Replace Q800. Yes Does DC level change at pin 14, IC6000, when speaker cut-off is toggled? No Replace IC6000. Yes Is composite audio present at pin 2, ICX2200? Check composite audio line. Replace IC1400(A).
Section 2: CB Chassis
CB Chassis Safety Guidelines X-RADIATION Observe the Anode voltage meter reading and compare with the table below for the proper CRT screen size. If the voltage reading is higher that the maximum, verify circuit component values and proper operation. To prevent possible exposure to radiation caused by excessive CRT Anode voltage, the CB Chassis incorporates a High Voltage Shutdown circuit.
Power Supply Introduction The CB chassis is a cold chassis designed to support 27, 32, and 36 receivers. Its power supply features a controlled turn-on MOSFET gate driver circuit, direct B+ regulation, thermal protection circuitry, over-current protection (OCP), over-voltage protection (OVP), over-load protection, provision for future universal power input (85VAC 265VAC), and software controlled degaussing.
CB CIRCUIT DESCRIPTIONS briefly drop. However, as the regulator begins to operate, it drives the chopper, and power derived from pin 13 of the transformer is drawn through DX3407 to maintain the voltage on CX3410. Overload and over-voltage protection are both internal to the regulator IC, and sensed through pin 4. Should either of these conditions occur, and latch will deactivate the oscillator inside ICX3412, thus eliminating any power supplied by the chopper.
Power Supply current ramp is input into pin 1 of ICX3412. This signal is then used to determine how regulation shall occur as described below. OCP is also sensed using this pin. To prevent a false over-current detection at startup however, a constant current sink has been included in the regulator. This measure is necessary due to a current spike that often occurs at startup due to primary capacitance discharge.
CB CIRCUIT DESCRIPTIONS The B+ provides power for deflection via the horizontal output transistor (HOT), QX3204, and for the tertiary voltages that come from the flyback transformer, TX3204. It also develops the +33VSB for the tuner through RX3413. The +12VSB is regulated down to +5VSB by ICX3402. This +5 volt source powers the microprocessor and EEPROM (IC6000 and IC6001 respectively), the Gemstar® board, the PiP board, and the tuner.
Microprocessor Control Introduction The CB chassis employs IC6000 as its microcontroller. All end user and servicer controls are accessed using this IC. While most of its functions will be described in terms of how they are used by other devices in the receiver, a number of facts concerning the microprocessor and its input devices will now be presented. The microprocessors job is to communicate control instructions and feedback information to and from various other processors and input devices in the set.
CB CIRCUIT DESCRIPTIONS sor from pin 49 along with the processed RGB. An exception to this occurs when Gemstar® is displayed. Under that circumstance, the fast-blanking pulse without RGB is sent to the video processor via the Gemstar® board.
Microprocessor Control the corresponding tuner to allow for clearer channel reception. The ideal voltage level here should be between +2.25 and +2.5 volts.
CB CIRCUIT DESCRIPTIONS signals entering IC2200 at pins 4 and 2 respectively and component video entering at pins 37 through 39. Note here that component video cannot be used as PiP. Lastly, pin 14 of IC6000 switches a DC level to alter the mute state of the audio amplifier. Memory The EEPROM, IC6001, is a small but vital part of the CB receiver. This 512 byte memory chip is responsible for storing servicer adjustments, channel information, and user settings, even when power is removed from the set.
IF Receiver Introduction The CB chassis utilizes two tuners in order to provide PiP without requiring a second external source. This is with the provision that the receivers antenna input is receiving multi-channel input. For example, a cable decoder box usually only provides a single channel input.
CB CIRCUIT DESCRIPTIONS comes from pin 11 of the tuner, is filtered, and is fed into pins 5 and 6 of the IFP. AGC (automatic gain control) voltage is applied to tuners pin 1 from pin 10 of the IFP. The +33VSB tuning voltage is applied to pin 9, while the +5VTune processing voltage is on pin 7. Clock and data lines from IC6000 communicate with the tuner on pins 4 and 5. In some receivers, the secondary tuners use the +9VIF at pin 6. IF Processing Each IFP is powered by the +9VSW on pin 9.
IF Receiver The remaining outputs of the IF processor are the AFC control to IC6000 from pin 14 and the IF video signal which passes through the AV-switch (IC2900) as it travels to the comb filter. AFC output voltage causes the microprocessor to determine any frequency corrections the tuner needs to make for a better signal. A portion of the luma from the IF-video is separated and filtered for the purposes of signal detection at pins 5 and 6 of IC6000.
CB CIRCUIT DESCRIPTIONS Jack-Pack The CB chassis provides multiple means for connecting external sources that supply video and audio signal. These provisions include two composite video (CV) inputs, two S-Video (Y/C) inputs, component video (YUV) input, corresponding left and right channel audio inputs for each video input, and, in some models, a front input jack featuring CV, Y/C, and stereo audio inputs. Additionally, a two-channel variable audio output is provided.
A/V Switching Suppose the user has composite video connected to the Video 1 input and S-Video connected to the SVideo 1 input. If the user selects video source 1 in the customer menu, the receiver must choose between the CV and the Y/C signal. Each Y/C input has a sensor line that feeds the micro. If the micro detects the presence of Y/C on video 1, IC6000 will direct the A/V switch to use that Y/C signal instead of the CV. Thus if it is present, Y/C has priority over CV.
CB CIRCUIT DESCRIPTIONS Component Video Component video is handled differently than the other jackpack inputs. The CB lacks conversion circuitry to make component (YUV) signal into CV. For this reason, component video cannot be used for PiP, which requires CV input, and is furthermore not separated (or combined) into luma and chroma through IC2900. YUV is directly input to IC2200 at pins 37 through 39. This arrangement necessitates the use of a YUV switch from the microprocessor to the video IC.
A/V Switching On sets using the digital comb filter, CV is fed into an A/D converter at pin 5 of IC2400. This IC is powered by the +5VTune at pins 3, 12, 20, and 27. Output for chroma is at pin 23 and for luma is at pin 25. Both are further cleaned by transistor circuitry that is powered by the +12VSW. Finally, combed luma and chroma are returned to the A/V switch.
CB CIRCUIT DESCRIPTIONS Introduction The CB chassis video features include two-tuner PiP, comb-filtered video, auto kine bias, half-tone video, and direct component video input to the video processor. Certain receiver models also include 2H digital comb filtering, Gemstars® Guide Plus, front A/V inputs, and scan velocity modulation. At the heart of the video circuitry is the NTSC video processor, IC2200. This video IC is powered by the +9VSWF at pins 33 and 44.
Video Processing limiter threshold (1.5 mA for 27, otherwise 1.6 mA), the corresponding voltage across C2204 triggers the limiter circuitry internal to IC2200, thus reducing output level (and therefore the contrast and brightness) of the RGB signal. ABL helps to prevent blooming in the sweep that would otherwise occur as high current draw lowers the sweep voltage. It also serves to extend the life of the picture tube.
CB CIRCUIT DESCRIPTIONS Before this processed video is pre-driven by transistors Q2205, 2206, and 2207, the video signal can be dimmed by the half-tone circuit. This circuit draws a limited amount of current when Q2209 is switched on by the half-tone pin 40 of IC6000. The half-tone circuit generates a rectangular area surrounding OSD in which video is present but shaded.
Video Processing AKB signal is derived from the collectors of Q5124, 5144, and 5164. These are fed back to the AKB circuit via pin 5 of the 5C2 connector and processed in the manner described above. The CRT board also features a setup jumper for optimal G2 adjustment. The purpose for it is to force DC voltage on the cathodes to be equal to the CRT cut-off voltage (170-190 volts DC with respect to G1). When jumped, the G2 setup circuitry grounds any incoming video signal.
CB CIRCUIT DESCRIPTIONS C5101 causes the G1 to become more positive. Since G1 is otherwise considered ground for the CRT, this action reduces any remaining CRT potential, thus eliminating afterglow. C5101 controls the rise time of this circuit, while C5106 controls the dead-time on response. Deflection Processing IC2200 also supplies deflection signals to drive the sweep section. Vertical drive is supplied in the form of positive and negative ramp signals on pins 13 and 14 respectively.
Video Processing supplies an E/W pincushion correction signal to IC3200, an op-amp in the deflection circuitry. This signal is calculated by IC2200 to correct horizontal deflection that would otherwise give a pincushion appearance due to the geometry of the CRT. IC3200 and its function is further described in the deflection circuit description. Note that it is only used in 32 and 36 CB receivers. Pincushion correction is wound into the deflection yoke on the 27 receivers.
CB CIRCUIT DESCRIPTIONS Introduction The CB chassis was developed to support CRTs ranging from 27 to 36. Major component of the deflection circuitry include IC2100, the vertical output IC; QX3203, the HOT (horizontal output transistor); TX3205, the horizontal drive transformer; and on 32 and 36 sets IC3200, the E/W pincushion correction amplifier. Of course the yoke, connected at 3Y3, and the flyback (or sweep) transformer, TX3204, are major components as well.
Deflection Control ment voltage, which is fed into pin 1 of the 2F5 connector, and pin 8s ABL signal. For the filaments part, since this voltage is needed only to heat the cathodes, it is not necessary that it be a DC voltage. ABL is fed to the video processor in order to regulate beam current.
CB CIRCUIT DESCRIPTIONS High Voltage Shutdown The x-ray protection (high voltage shutdown) circuit uses the current from pin 6. DX3002 and CX3003 convert this current to DC. The resulting voltage is applied to the resistor divider network in the emitter circuit of QX3002. Voltage applied to the base of this transistor remains constant because of the zener diode, ZDX3004. If HV reaches 35.7 kV (33.9 kV for 27 sets) DC applied to the emitter of QX3002 will switch the transistor on.
Deflection Control Both positive and negative vertical ramp signals are required for operation. IC2200 supplies these to pins 4 and 5 of the amp as non-inverting and inverting input. Pin 3 is an input for output stage VCC. Pin 7 is the pump-up output. Vertical output comes from pin 2 of the amp to pin 4 of the yoke connector. The other end of the yoke provides feedback to pin 5 of the vertical amp and to the horizontal pincushion correction circuit.
CB CIRCUIT DESCRIPTIONS Width and Geometry Correction East/West pincushion correction is performed by circuitry built into 32 and 36 sets. The windings of the yokes used in the 27 CB chassis have this correction shaped into their design at assembly. Correction is necessary on larger sets due to their geometry. As the CRT electron beam approaches the upper and lower extremes of the screen, its horizontal scan lines sweep a wider length than they do in the middle of the screen.
Audio Development Audio Processing The CB chassis uses IC1400 to process audio. This IC features true MTS (Multi-channel Television Stereo) sound, dbx noise reduction, and SAP (second audio program) processing. Its I2C bus at pins 9 and 10 allows adjustment for volume, balance, tone control, front surround sound, SAP switching, source selection, and stereo separation. IC1400 is powered by +9VSB at pin 24 and grounded at pins 22 and 11.
CB CIRCUIT DESCRIPTIONS Audio Boost Those sets that have the audio boost feature output audio signal on pins 43 and 44 to IC1401. This IC is powered by the ±14AUD. It strengthens the audio signal and returns it to pins 41 and 42 of the audio processor. From here, the boosted signal is output from IC1400 on pins 6 and 7.
Audio Development The +22VSB is supplied to pin 10. Pins 4, 9, and 12 are grounds for the amp. Pins 5 and 2 input left and right (L/R) channel audio fed through C851 and C861, which eliminate any DC accompanying the signal. Pin 3 provides a reference voltage. L/R output comes from pins 7 and 11. Pin 8 is a line that, upon receiving a switching DC level from the micro, mutes the speakers. This occurs when the user selects the speaker cutoff option.
CB TROUBLESHOOTING Start 1. No Power Is AC connected? No Plug receiver into AC source. Yes Does FX3401 conduct? Replace ICX3403, ICX3406 as necessary. Replace FX3401. No Yes Is B+ present at CX3420? No No Yes Yes Is +12VSB present across CX3427? Is pin 3, ICX3412 switching? Yes Check RX3423. Replace TX3401 if necessary. No Yes Is +5VSB present across C3426? No Replace ICX3402. Yes Does pin 32, IC6000 emit a DC pulse at startup? No Replace IC6000.
Flowcharts 2. Shutdown Start Does the set power up for more than 2 seconds? No No Check microprocessor ciruitry. Yes Yes No Does the Vp-p level at pin 18, IC2200 stay below 1.0 volts? Check HVshutdown circuit, sweep transformer. Does the set shutdown after just 3 seconds? Yes Check IC2100 & CRT protection circuit. Is B+ running at a constant DC level? No Replace ICX3412.
CB TROUBLESHOOTING 3. No Tuning Start Are all tuner voltages present? (Refer to schematics.) No Check tuner power supplies. Yes Is IF present at pin 11, WT1200? No Does changing the tuner fix the problem? No Check IF line. Replace U1200 if necessary. Yes Is IF present at pins 5, 6, IC1200? Yes Is IF present at pin 17, IC1200? This procedure may be applied to the 2nd tuner section as well. CB-32 No Yes Refer to No Audio and No Video Troubleshooting. Check IC1200 power supplies.
Flowcharts 4. No Video Check TX3204 for high voltage. Check HOT and H-drive circuit. Yes Yes Start Is raster present on the screen? No Is 1.07 kVp-p signal present on collector of HOT? No Is regulated B+ present at pin 3 of TX3204? No Check Q2901 and +9VSW source. No Check power supply. Yes Is there luma at pin 4, IC2200? Yes Replace IC2200. No Is RGB output present at pins 22 - 24, IC2200? Yes Check Q2205, 2206, 2207.
CB TROUBLESHOOTING 5. No Audio Start Is +22VSB present on pin 10, IC804? No Check audio power supply. Yes Does DC level change at pin 14, IC6000, when speaker cut-off is toggled? No Replace IC6000. Yes Is L/R channel audio missing at pins 2, 5, IC804? No Replace IC804. Yes Is L/R channel audio missing at pins 6, 7, IC1400? No Check L/R channel lines. Yes Is composite audio missing at pin 19 of IC1400? No Check IC1400 VCC. If it is present, replace IC1400.
