Yaesu FT-857 Technical Supplement

Contents

Yaesu FT-857 Technical Supplement Manual pdf 12 page image

12AlignmentIntroduction and PrecautionsThe following procedures cover adjustments that are notnormally required once the transceiver has left the facto-ry. However, if damage occurs and some parts subsequent-ly be replaced, realignment may be required. If a suddenproblem occurs during normal operation, it is likely dueto component failure; realignment should not be done untilafter the faulty component has been replaced.We recommend that servicing be performed by authorizedVertex Standard service technicians, experienced with thecircuitry and fully equipped for repair and alignment. If afault is suspected, contact the selling dealer for instruc-tions regarding repair. Authorized Vertex Standard ser-vice technicians have the latest configuration information,and realign all circuits and make complete performancechecks to ensure compliance with factory specificationsafter repairs.Those who do undertake any of the following alignmentsare cautioned to proceed at their own risk. Problems causedby unauthorized attempts at realignment are not coveredby the warranty policy. Also, Vertex Standard must re-serve the right to change circuits and alignment proce-dures in the interest of improved performance, withoutnotifying owners.Under no circumstances should any alignment be attempt-ed unless the normal function and operation of the trans-ceiver are clearly understood, the cause of the malfunc-tion has been clearly pinpointed and any faulty compo-nents replaced, and the need for realignment determinedto be absolutely necessary.The following test equipment (and thorough familiaritywith its correct use) is necessary for complete realign-ment. Most steps do not require all of the equipment list-ed, but the interactions of some adjustments may requirethat more complex adjustments be performed in a se-quence. Do not attempt to perform only a single step un-less it is clearly isolated electrically from all other steps.Rather, have all test equipment ready before beginning,and follow all of the steps in a section in the order theyare presented.Required Test Equipmentm Digital DC Voltmeter (high-Z, 1 M-Ohm/V)m DC Ammeterm RF Millivoltmeterm AC Voltmeterm RF Standard Signal Generator w/calibrated output anddB scale, 0 dBμ = 0.5μVm Signal Generator with calibrated outputm Spectrum Analyzer good to at least 1 GHz.m Frequency Counterm 50-Ohm Dummy Load (200 watts)m 100-Ohm Dummy Load (200 watts)m 150-Ohm Dummy Load (200 watts)m In-Line Wattmeter (200 watts, 50-Ohm)m Linear Detectorm RF CouplerAlignment Preparation & PrecautionsA 50-ohm RF Dummy load and in-line wattmeter must beconnected to the main antenna jack in all procedures thatcall for transmission, except where specified otherwise.Correct alignment is not possible with an antenna.After completing one step, read the following step to de-termine whether the same test equipment will be required.If not, remove the test equipment (except dummy loadand wattmeter, if connected) before proceeding.Correct alignment requires that the ambient temperaturebe the same as that of the transceiver and test equipment,and that this temperature be held constant between 68 °F~86°F (20°C ~ 30°C). When the transceiver is brought intothe shop from hot or cold air, it should be allowed time tocome to room temperature before alignment.Whenever possible, alignments should be made with os-cillator shields and circuit boards firmly affixed in place.Also, the test equipment must be thoroughly warmed upbefore beginning.Note: Signal levels in dB referred to in this procedure arebased on 0 dBμ = 0.5 μV (closed circuit).