RCA CDP18S711 Instruction Manual
                                                       | |
Contents
|
VIL Troubleshooting HintsThis section is aimed at helping you diagnose and fixhardware problems should they occur. First, check allIC's to make sure they are properly inserted in the PCcard. An IC inserted in the wrong direction can bepermanently damaged. Check that the +5 V DC supplyvoltage ripple does not exceed 0.2 volt. Visually inspectthe PC card for solder shorts or bad solder joints. Try toavoid zapping your PC card with static electricitycharges. Discharge youself, if necessary, by touching agrounded object before touching any IC's or PC cardwiring.No SoundIf everything works but you don't hear any soundfrom the speaker you probably have a bad U15, badspeaker, or bad connection. Flip RUN up with key Cdown. Hold any key down and the Q light should comeon. Check the Q line if it doesn't. The Q line should be at+5 V with a key held. If the Q light is on, but with notone, check U15 and your speaker connections.No DisplayIf you get no display but do get operating system keytones, check the video output signal. First, select theoperating system to make sure video should be present.The video signal should be 0.5 volt peak to peak orhigher. You should see negative-going vertical andhorizontal sync pulses and positive-going video pulses.The sync pulses should be about 25% of the total swing.Check your display system and interconnections if youhave the video signal present. Make sure you are usingthe correct high-impedance input setting, for example.Other Problems27Using operating system mode 0, load bytes into RAMusing all 16 hex keys. If a key doesn't work or shows thewrong value on the display screen, check the keyboardand U13.If everything except the cassette interface works,check U14. Review the cassette recording guidelines inAppendix A. Use the cassette phase and data testprocedures described in Appendix A to find out what'swrong.If you can run some programs but not others, youmay have a bad RAM bit. Load and use the memory testprogram provided in Appendix A. Try changing RAMchips, one at a time.If nothing seems to work and you can't run theoperating system, check your power supply and PC cardwiring for shorts again. If everything still seems OK youwill have to start signal tracing.Signal TracingCheck the U3 oscillator output. If not present, replaceU3. If the 3.521280-MHz signal is present, check the U4divider. Replace U4 if it isn't toggling. Make sure youuse a 7474 type. With RUN up, you should see TPA andTPB pulses being generated at pins 33 and 34 of U1 Ifthey are not present, check the RUN level to make surethe switch is working, then replace U1.Check the output of U6B to make sure that the ROMis initially selected when RUN is first flipped |
Related manuals for RCA CDP18S711
This manual is suitable for:
manualsdatabase
Your AI-powered manual search engine