Ten-Tec Argonaut V Repair Manual

Ten-Tec Argonaut V (Model 516) Low Output Repair
(Note: Those undertaking this repair do so at their own risk. The
procedures outlined located a faulty band-switch diode and worked for me.
Your circumstances may differ (i.e. the problem may be another component).
This procedure has not been approved by Ten-Tec, Inc. or any of its staff.)
Symptoms:
My Argonaut V developed a problem with low output power on all bands except 80
metres. The output on 80 was 20 watts on 160 it was 12 and on 40 metres 10 watts. On
the upper frequencies power dropped off to approximately 1 to 2 watts.
Troubleshooting:
Section 4.5.1 and 4.5.2 of the manual describe the transmit band switching circuit. The
circuits are in schematic diagrams Argonaut V Pwr Amp (pages 2, 3 and 4 of 5).
The switching circuit applies approximately +8 volts to the appropriate band circuitry and
connects the power amplifier with the rest of the transmitter section. All other bands
should have approximately –150 volts (with the Argonaut V at full power).
With the top off of the rig you can access all the necessary test locations to determine if
the band switch circuitry is functioning properly (use caution). A series of coils are
located on the circuit board (see figure 1) that is attached to the heat sink. These coils are
a part of the various band-switching stages and are connected to the Bandout rail. They
are identified as 160 metres (L32) at the left, L28, L24, L21, L18, L15 and end with the
15 through 10 metre coil (L12) at the right. (The latter coil is air wound all others are
wound on ferrite cores.)
Figure 1: Test points (PA board removed from rig)
Test voltages can be checked with the PA board in the rig and the top cover removed.
The voltages (referenced to chassis ground) are measured where the coil is attached to the
Original document located at:
https://www.ve7tk.ca/