QRPKits DC20A, Руководство пользователя

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2/14/2007 Page - 15
Trouble Shooting Guide
The most common reason a kit does not work right is due to soldering issues. Therefore, the first thing to look for if
something doesn't work is the solder connections. Look for solder splashes that might be shorting two pads
together and shouldn't be connected. Also, for solder which that might have stuck just to a lead and didn't flow into
the circuit board pad, e.g., cold solder joints. Connections to the ground plane need extra heat, so look closely to
these connections to make sure the solder flowed into the hole. It’s also possible to have solder on the circuit
board pad, but it didn't flow around the lead.
The second most common error is misplaced parts. You may misread a resistor color code, or put it in the wrong
spot. The same goes with capacitors. So, if your soldering looks good, double check the parts placement.
Having an actual bad part is rare. It is possible to damage them though. The 2N7000 can be damaged by static
due to improper handling and ICs can be damaged if they are installed backwards.
Some DC voltage levels are shown on the schematic, along with some wave forms. Note that the DC voltage
across R22, the crystal oscillator emitter resistor measures a lot higher than the base voltage, because of the way
the DVM responds to the superimposed AC RF voltage.
Low Audio
The DCxx audio output is adequate for most headphones especially the higher impedance versions. If you are
experiencing low audio try a different headset. Those with the highest sensitivity ratings are the best.
If you still find the volume too low, you can add a simple audio amplifier. Several circuits and kits using the popular
LM386 ICs can be found on the internet.
A mini audio amp, 2cm x 2cm x 10mm, assembled and tested with 2.5 inch attached leads is available from
W5USJ. This amp can be attached in place of R6, 10 Ohms, or in series with the headphone jack using suitable
connectors. For more details, visit: http://www.w5usj.com/miniaudioamp.html, email w5usj@qrparci.net.