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1990-10-14
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SB-043
TS-520S -6v Supply Failure 8-9-79
When troubleshooting a TS-520S, check all power supply voltages, including
the -6v DC supply. Symptoms such as dead, blown 2A DC fuse and now dead,
low RX, no TX, or similar may occur after switching between 80 and 40M.
Cause of failure may be traced to an intermittent shorting between the 14v
dc and -6 dc supplies as the band switch is rotated between 40 and 80
meters. This will weaken or destroy D8, a 6v zener on the FIX CH AVR unit.
To prevent repeat failures, break the White lead and install a 22 K ohm 1/2
watt resistor at the bandswitch S5-6, between the -6v supply line and
switch terminal. An of course replace D8 on the FIX CH AVR unit, X43-1100-
00
New Part: 22 k ohm 1/2 W carbon resistor
Please annotate your service manual.
JEB/yn
(c) 8979TKC