TS120

TS-120S TX OSCILLATION

The TS-120S may exhibit intermittent oscillation on one or more bands.
Cause may be either external or internal. Symptoms may be no control of
Carrier level, full current or ALC in either CW or SSB after initial keying
or modulation, or "full outup both forward and reflected".

EXTERNALLY INDUCED OSCILLATION:

For oscillation which occurs only when operating on an antena, suspect RF
feedback coupled through the mic, key, or other auxiliary wiring.

  1 - Add a .01mf bypass cap across the mic connector, pins 1 & 4.
  2 - If not already present, add a .01mf cap across pins 3 & 4 on the mic
      connector.
  3 - Add a ferrite bead at the base of the mic preamp Q18. This may be
      installed on R42.

INTERNAL OSCILLATION

  1 - Make certain the antenna fitting is tight to the rear panel.
  2 - Check for loose screws securing the Relay unit X41-1250-00 (located
      over the RF unit X44-1260-01). Add star washers if necessary.
  3 - On the RF unit, check the DRV (Drive Output) coax for snug, secure
      connection at both ground and center condutors. Follow this coax
      to the final unit X53-1250-00 and again check for secure connections.
  4 - On the RF unit, check diodes D2, 3 & 8 for hight reverse leakage.
      Lift one end of each diode and mesure with an ohmmeter. If in doubt,
      replace.