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Wise words - cheers Bob73 Bob G4KSG
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-------- Original message --------From: "Robert Curry [email protected] [FT100]" <[email protected]> Date: 10/05/2018 05:53 (GMT+00:00) To: [email protected] Subject: [FT100] Finals and RF output
#1, before removing transistors, TESTING to determine operating status and voltages should be conducted as a part of preliminary troubleshooting! While keyed in transmit SSB mode, but with Mike gain set to ZERO, and using a HF frequency, you should have a voltage exceeding 1.0 volt but less than 5 volts on all GATE terminals of the HF driver and final transistors, and 13.8 volt supply voltage on the drain terminals of these driver and final devices. If these voltages are missing or incorrect, the CAUSE must be determined! Note that use of other than factory supplied or recommended microphone may NOT properly activate the FT-100 transmit function, as unlike most other radios, it requires a high-resistance in series with the PTT Mike circuit to function properly, the stock Mike provides this-about 22 or 27 thousand ohms.) With power disconnected, resistance to ground at the GATE terminals should be measured, if abnormally LOW, (less than 1000 ohms) there is a problem! Be awar
e, there are "jumpers" -little black plastic push on type, as used in hard drives and on mother boards, that can affect gate bias, be sure they are clean, and properly contacting. Should readings then indicate a possible bad transistor, after careful removal, voltage and resistance should be retested before installation of replacements, and always turn bias voltage DOWN before installing a NEW FET, so as to avoid possibly destroying it by excessive current at power up! If not skilled and equipped to perform these tasks, you should refer it to someone that is, to save parts and money. Service menus should not be accessed unless a voltage of 13.8 volts is being used and supplied to the radio, as different voltages ( 12.3 volts, or 14.5 volts, for example) may corrupt the alignment settings!-73, KC3VO, Bob.
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