Rapid Jumps In Vfo Frequency; Receive [Rx] Signals Intermittently Drop Roughly 40 Db; Receiver Agc-Overshoot, Causing Receive Audio-Distortion On Voice-Peaks And Concurrent S-Meter Overshoot; Television Interference With The Radio Transmitting Into A 50 Ohm, Shielded Termination - Kenwood TS-830 Survival Manual

6.17

Rapid jumps in VFO frequency

Cause(s): [1] This can be caused by fluctuation in the 9V regulated power-supply voltage,
which is the result of an intermittent connection between the AF-AVR [automatic voltage-
regulator] Unit's circuit-common and chassis ground. [2] The problem can also be caused by a
dirty ground-connection wiper on the rotor of the VFO tuning-capacitor.
Fix(s): [1] Solder a wire to the "TPG" terminal, next to C81, on the AF-AVR Unit. On the other
end of this wire, solder a #6 ground-lug with locking teeth. The ground-lug is placed under one
of the nearby sheet-metal-screws that fastens the AF-AVR Unit to the chassis. [2] Remove the
VFO from the radio using a 3 mm Allen-wrench. Pull the pilot-lamps from their grommets and
pull the electrical plug from the rear of the VFO assembly. Remove the VFO shield-can {5,
Phillips-head screws} and clean the gummy grease from the wiper on the tuning-capacitor's
rotor shaft with solvent. Lubricate the wiper with contact cleaner.
6.18

Receive [RX] signals intermittently drop roughly 40 db

Cause: This is usually due to a poor electrical connection at the crimps on the contact-pins at
the ends of the "RIF" [receiver intermediate-frequency] coax cable, which is above the chassis.
This cable carries the 8830 KHz RX signal between the RF Unit, Connector-5, pin 2, {to right
of VFO} and the IF Unit, Connector-6, pin 6, {to left of VFO}. The crimped-on pins in these
connectors have a tin-plating. The coax has copper conductors which, along with moisture from
the air, creates a dissimilar-metal electrolytic action that eventually turns the crimp-connection
into a semi-insulator.
Fix: Make a good electrical connection between the copper and the tin-plating, where the
center-conductor wire protrudes beyond the crimp, by applying solder or a conductive-paint
{neater than soldering and easier to use} such as GC Electronics Co. Silver-Print. This paint can
be applied to the target area with the end of a partially straightened paper-clip. To remove the
female pins from the connectors, using a jeweler's screwdriver, depress the pin's ratchet-tab,
which is accessible through the slot in the side of the connector and simultaneously pull the
contact and wire out through the back of the connector. To avoid mixups, remove one pin, repair
and replace it before removing the next pin.
Note: It is easier to gain access to Connector-5, on the RF Unit, if the Counter Unit is moved
slightly {4, Phillips-head screws}.
6.19 Receiver AGC-overshoot, causing receive audio-distortion on voice-
peaks and concurrent S-meter overshoot
Cause: Too-much R/C delay in the AGC-bus at the second-gate of Q1 on the RF Unit.
Fix: Replace R12 [1M Ohm] with a 10k Ohm to 51k Ohm unit. Q1 and R12 are located at the
front, left of the RF Unit. It is possible to clip the leads of R12 from the top of the circuit board
and install the lower-R unit without removing the RF Unit from the radio. An alternate method
is to remove the AF-AVR-Unit and remove the cover plate that is underneath it. This allows
easier access to the trace side of the RF-Unit circuit board.
6.20 Television interference with the radio transmitting into a 50 Ohm,
shielded termination
Cause: This is usually caused by VHF harmonic energy leaking out through the line-cord.
Fix: Add one or two, µ=850, VHF-attenuator ferrite beads in series with each of the two wires
in the line-cord. It is also helpful to add a approx. 470 pF, 1 KV, disc-ceramic, bypass-to-ground
14