Page 19 January February 2018 TCA

Figure 2: Part of the S-meter circuitry for the Yaesu FT-ONE transceiver. The S-meter connection is shown near the left hand bottom edge,
labelled SM. My thanks to Yaesu for permission to reproduce this diagram.
From the IF unit, the S‑meter signal goes between circuit boards was faulty and my
to another board where a relay switches prodding and prying while making
the meter function between S‑meter on measurements was sufficient to clean the
receive and ALC on transmit, as shown in contact.
Figure 4 on the right. I checked this relay
and found it to be working properly. The relay shown in Figure 4 connects the
meter to measure signal strength on
After wiggling some more connections receive and ALC on transmit.
while making
measurements, The terminal marked
all of a sudden S‑meter in the Figure is
the S‑meter connected to pin 32 of
started working the IF unit and the middle Figure 4: The relay circuit. The relay itself is
properly and it terminal goes to the front located on a separate plug-in circuit board so
hasn’t stopped panel meter of the radio. good connections at the plug-in sockets are
working since. This radio is now quite essential for the proper operation of the meter.
old but I like it very much I think the key things needed for repairing
I still don’t know radios are time and patience. Usually not
what the and, as was the case much equipment is necessary. A digital
problem was with its previous owner, multimeter is essential and an
for sure, but I I have had many very oscilloscope and some kind of signal
suspect one of enjoyable hours using it source can also be very helpful. A radio
the plug‑in and much pleasure from like the FT‑ONE transceiver, with its
connections its operation. through‑hole parts, is probably easier to
I am very pleased that so
Figure 3: The far I have been able to fix work on than more modern equipment
integrated using surface mount components, but
circuit Q9025 any problems I’ve Alan Wolke’s videos show that this kind of
is located encountered. If the meter equipment can be also repaired by tracing
near the gives me any more through the circuit and doing a careful
centre of this trouble I now know where
photo. The to look, and each time I analysis of the problem. Finally, as with
S-meter most things, practice and the learning that
connector is do some work on the comes with it, really help one to improve.
the metal tab radio I learn more about
third from the it and about radio I wish all of you all the best for 2018 and
right at the circuitry. as always, you can contact me at
bottom. vy1kx@rac.ca.
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