User manual AUDIOVOX MS-220

[. . . ] TAPE DOOR TUNING KNOB Rotate the knob to tune the desired broadcast frequency. VOLUME KNOB Rotate the knob to increase or decrease the volume level. FADER KNOB Rotate this knob to left or right for desired sound balance from front to rear speakers. DISPLAY AM/FM BUTTON Press this button to change from AM to FM band. [. . . ] These residues should be cleaned after 50-100 hours of accumulated tape operation. You can use a cassette cleaning cartridge available where ever stereos are sold. De-Magnetizing The movement of the magnetic tape head and metal parts cause a magnetic field to develop. We recommend you have the tape player demagnetized at least twice annually. You can purchase an inexpensive tape head demagnetizing tool to do this yourself. 5 TROUBLESHOOTING CHART AM/FM RADIOS Symptom No Power No 12VDC Cause Possible Solution Check circuit fuse at source Check in-line fuse on power lead Power lead disconnected Ground connection disconnected Circuit fuse at source In-line memory lead fuse Check for shorting of speaker leads to ground Check for proper speaker wiring. Note: Radios have a sticker on them explaining wiring color code. Power indicated; No audio output or very distorted sound No 12VDC to memory lead (electronically tuned units only) Speaker Output shorted Speaker out cross channeled 6 Only one channel (right or left side) Radio Balance Speaker Disconnected Speaker lead shorted or grounded Speaker wiring shorted or positive lead grounded Speaker terminals grounded or shorted Popping in one or both channels Check radio function Check speaker connection at radio and/or speaker Check speaker wiring continuity to ground w/tester or meter Leads from speaker cone to terminal touching metal basket or speaker No AM Reception Antenna disconnected Antenna mast grounded or shorted Antenna center lead broken Connect antenna Check antenna or substitute with antenna known to be good Check antenna or substitute with antenna known to be good Note: Antenna leads can be tested with continuity or multi-tester. Some may have electronic component (capacitor) built in which will not allow it to be tested. 7 APPLICATION NOTES AM/FM RECEPTION Some boats have more than one AM/FM radio. The best way to insure good reception is to supply a separate antenna for each radio. Other options available to supply adequate AM/FM reception to these radios are listed below, along with some general information in regards to radio reception. AMPLIFIED AM/FM ANTENNA A popular second antenna that can be used is our AB-100 amplified AM/FM antenna. It is small and has a retractable mast that can be mounted vertically or horizontally. This antenna provides good FM reception, but the AM reception will be compromised to some degree because of the length of the mast. "Y" ADAPTERS The " adapters used to connect one Y" antenna to two radios will only provide AM reception to one of the radios and will compromise both AM and FM reception. MAST LENGTH AM/FM antennas compromise AM reception by design. The optimum mast length for FM is approximately 30 inches which is standard for most automotive antennas. The optimum mast length for AM reception is over 100 inches which is not practical for mobile applications. 8 Special circuitry in electronic tuned radios or AM trimmers in mechanically tuned radios, make up for some of this difference in optimum mast length for AM reception. FM RECEPTION FM reception can be received with a very limited antenna and strong local FM stations can be received without an antenna, depending on the circumstances. ANTENNA CABLE Increasing the antenna lead cable length (adding extensions) will reduce sensitivity of AM with electronic tuned radios. CONCLUSION AM/FM reception is subject to the choice of an antenna and it' application. There can also be s a variety of methods used to supply signal to both primary and secondary radios, but AM performance is the ultimate " test" . It appears that consumers or end users are becoming much more critical when it comes to acceptable antenna performance. It may be necessary for manufacturers to re-evaluate what was once considered acceptable. GROUND PLANES Ground planes are also important when considering antenna performance. Most automotive antennas are designed to be mounted on the metal body of the vehicle. The metal body reflects the signal interference generated by the vehicle' electrical s system while it also provides the ground for the antenna lead shield. All this is necessary in order to maintain a good signal, especially AM. 9 APPLICATION NOTES Voltage This note will discuss DC Power sources and how they relate to 12 volt DC video products. [. . . ] Noise may result and the line fuse may fail. Ignition Systems Unwanted noise generated from the ignition systems used to be a big problem. However, with more sophisticated filtering circuits designed into audio/video products, these problems are not as wide spread. Changes in wire harnessing also has contributed to the decline of application problems. Use the same ground point for all related products. [. . . ]