Vectronics VEC-1002K - Manual (Page 26)

VEC-1002K Owner's Manual 2 Meter FM Receiver Kit
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Does not turn on: Check battery condition, snap clip, and power leads. Also,
make sure lead polarity is correct (red to +, black to GND). Make sure power
switch is "on".
Also, squelch may be locked "on" (see following). Check operating voltages.
Turns on, does not receive signals: Check antenna, antenna lead, and plug for
shorted or open condition. Also, radio may not pick up signals in metal building
without an outdoor antenna.
Drifts off-frequency rapidly, "motorboats", weak audio: Symptoms of a
weak battery or insufficient operating voltage. Be sure to check battery voltage
"under load" (with the radio turned on).
Squelch won't open when control is fully counter-clockwise: Check the
value of the squelch potentiometer. It must be 100K. If a 10K pot is installed at
R10, the squelch won't open.
Poor sensitivity: Look for antenna problems. Check condition of L1, L2, L3.
If they are improperly shaped or if a lead is broken, sensitivity will be poor.
If these checks fail to uncover the problem, repeat the "QC" check one more
time. Service records show that, for most malfunctioning kits, outright
component failure is relatively rare. In most cases, the culprit is a misplaced
part, reverse-polarized capacitor or diode, or a faulty solder connection!
Voltage Analysis: One effective way to pin-point where a circuit problem
might be is to use voltage analysis. To do this, you'll need a voltmeter--
preferably a high-impedance DMM type. Set your meter to the 10-volt dc range
and clip the black (-) test lead to a ground point on the PC board (the frame of
the antenna connector is a good point). Make sure the radio's battery is fresh--
the chart readings were made using a 9.0-volt power source. Using the red (+)
lead, check the voltage on each IC pin and compare it against the voltage chart
below. Readings should be within 10-15% of chart value:
MC13135 (U1) MC34119 (U2) 2SC2498 (Q1)
Pin Voltage Pin Voltage Pin Voltage E B C
1 5.2 13 5.2 1 0.1* .77
2 4.5 14 0.1* 2 4.0
3 4.3 15 0.1* 3 4.0
4 5.2 16 0 4 4.0
5 4.7 17 2.3 5 4.0
6 5.2 18 5.2 6 8.8
7 3.8 19 5.2 7 0
8 0 20 4.0 8 4.0
9 4.4 21 5.2