FX 146
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100
Stage G: The PLL Synthesizer: Understanding and Assembly
FX-146
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47
despite the detail of our explanations, be sure you set one channel up for
146.52 MHz Simplex before you pursue troubleshooting. It is very important
to have a clear understanding of how to program the frequency synthesizer
and offset matrixes of your transceiver.
It's fairly easy to double-check "obvious" details such as IC orientation, diode
polarity, electrolytic capacitor polarity, and those other construction
essentials that we stress repeatedly. SOME of the more subtle assembly
errors which take very careful checking to find include the following:
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Any use of 2N3904 where VHF 2SC2498 is required
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Use of NPN where PNP is required: Q12,Q13,Q14
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Mistaken use of .01 or .001 disc capacitors where a small picofarad
value is specified.
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Major error in selecting resistors with similar color codes, like 100 ohm
(brown-black-brown) used for 100K (brown-black-yellow), or vi ce-versa.
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Reversal of the 8V and 5V voltage regulators
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L16, L14 or L13 touching the top groundplane.
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A single IC pin or IC socket pin bent under the plastic body of the device.
Simple operational tests are discussed at the end of most of the assembly
stages. Use these as a guide for tracing the circuit. If you make the effort to
understand each of the small sections of the big picture, you should have no
trouble in identifying the source of your problem.
If tracing and repairing complex circuits is new to you, we urge you to retrace
your assembly steps thoroughly. Take the extra time to really understand
circuit functions that might have been hazy during the excitement of
construction. Use basic LOGIC to narrow down the problem to a specific
stage.
If you ask a more experienced ham friend to look at your unit, it is up to you
to be able to recognize whether this person has the know-how and proper
equipment and tools to be of real help to you. Most hams really WANT to be
helpful, but good intentions are no substitute for competence. (If your friend
drags out the trusty soldering gun and big, rusty alligator clips, suggest a
fishing trip or antenna-fixing party instead!)
The best favor any friend can do for your kit project is to review the
correctness of part choices.
Factory Service is, of course, available at prevailing shop rates. The hams at
Ramsey enjoy providing kits to hams and hobbyists in addition to our Test
and Measurement Division work, and we're sure that you understand that
our company is not a ham club, and that our professional technicians aren't
