Hi folks,
just repaired another TS-770 and I would like to share some hints with you other radio-guru's...
- Completely dead TS-770: after long transmission times the 13.5 Volt pre-regulator often burns out. The printed circuit board is most of the times completely burned and irrepairable. No problem: The real power regulator transistor is still alive in the 144 MHz pa compartiment. Mount an extra 7815 regulator on the back-cooling panel. Connect input (pin-1) to the collector of the series regulator transistor. Disconnect the base from the board and connect it through a 1N4001 diode to the output (pin-3) of the 7815. This gives 13.7 V output. Don't forget decoupling caps 1 uF on in- and output of 7815.
- Deaf 70 cm receiver: the input transistor tends to short B-E. Replacement of this exotic beast is possible by mounting a BFW92A or BFR91A on the solder side of the board.
- Erratic dial: due to bad contacts in the two adjustable resistors on the encoder board. Just moving the slider a bit solves the problem for the next year...
- Don't forget to turn down the two deviations pots as the rig is already open. Standard deviation is 7 kHz for these old transceivers, a big crime in these 12.5 kHz spacings. 3 kHz peak deviation is the european standard nowadays.
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