The first thing to do is check for unsoldered pads and for solder bridges. In almost every case, this will be your problem.

Touch all the components with a finger while looking at the foil side for loose wires. Check any components that feel loose. Use a small screwdriver to scrape off chunks of rosin and push on pins to make sure they are well soldered.

The best place to check for solder bridges are at the components that have pins spaced .1 inch apart. Look carefully at the following parts: NE602's, L2, L3, C12, C21, C14, TDA2002, 7805 voltage regulator, and the VFO circuit (pins 6 & 7 of U1).

Check a 5 volt pad for voltage. If no voltage, make sure the regulator (7805) is placed correctly on the board. Then check R10, R1, and R11 for solder bridges to ground. Make sure the back of the regulator is not touching the heat sink of the TDA2002 audio amplifier.

Place a jumper between the antenna and pin 3 of L2. You should hear WWV. If not, place your finger on the plus "+" side of C21. You should hear a 60 cycle hum out of the speaker. If there is no hum, look at the audio amp circuit. With an ohmmeter, check resistors for correct values. Check the electrolytics for proper polarity ("+" side next to "+"). Always be on the lookout for solder bridges. Make sure you have an 8 ohm speaker and that it is good.

If the audio amp is working and you still do not hear WWV, the places to check are the MMIC and U2. At the present time of the sunspot cycle, WWV can be received best during the day. If WWV does not work for you, use a simple 10MHZ crystal oscillator for a calibration signal.

Touch your finger to the input side of the MMIC (crystal filter side). If you live in a large metropolitan area, you should hear AM broadcast stations. Jumper your antenna to Pin 3 of L2, WWV should be heard. If you do not hear WWV, and the "BFO ADJ" makes no difference in the tone of the background noise, then the BFO is not working.

Check oscillation by tuning a general coverage receiver to around 10MHZ to find the signal or use a frequency counter at pin 7 of U2.

Check for unsoldered pins at pin 6 & 7 of U2, solder bridges between the pins of U2, the BFO crystal, RFC2, and C16.

Look for the notch on the NE602 and the dot on the T4-6T transformer to double check correct position. Check for 3-5 volts at pin 8 of U2 (NE602) and at the MMIC side of R1. The voltage at the ungrounded side of the diode at full volume should be zero. The "banded side" of the diode should be connected to ground.

If the volume control does not work (receiver stays at full volume), look for a bad diode or RFC1 open (burned up). When the volume control is not connected, the receiver stays at full volume and there is zero voltage at the anode of the diode (opposite side from the band).

If there is a loud "squealing" noise from the loudspeaker and the volume control makes little difference, replace the diode.

The number on the MMIC, "1651", should be toward the crystal filter. If you are in the city with very strong AM signals, you can touch the input (crystal filter side) with your finger and hear AM broadcast stations.

When C16, the "BFO ADJ" trimmer, does not produce a changing tone, and WWV can be heard, the BFO is out of range.

Check for the proper value of RFC2. If the 180UH choke was placed there, the BFO will be out of range. Make sure that RFC2 is 22UH. Sometimes it is possible to mistake a choke for a resistor and vice-versa. The resistors in this kit have rounded ends, whereas the chokes have square ends. Also, the chokes have a wide silver band at one end.

Double check capacitors C27 and C28 for proper values (C27-33PF, C28-15PF). The circuit is simple. If you have oscillation, you are out of range. Use the fine tuning techniques from the section "BFO ALIGNMENT".

When WWV is heard, but the receiver is not working in the band you want, the problem is the circuit around U1 (NE602), or the incorrect placement of L2. Check L2, the dot should be next to pin 1. Check for voltage at pin 8 of the NE602. Using a general coverage receiver or a frequency counter, check for correct frequency and oscillation of the VFO (pin 7 - NE602).

Check the windings of the input toroid. If an ohmmeter check between the primary and secondary windings shows a short, re-check your wiring. There should be no continuity between the primary and secondary windings.

There should be continuity between the secondary ends and the secondary tap. If not, then the bifilar secondary wires are connected wrong. Go to Step 7 and re-check your connections.

If you suspect a bad U1 (NE602), place it at U2 and see if it works there. Look closely for solder bridges underneath C32, C35, and between the pins of U1, L1, and L2.

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Last Update: 04/20/97
Web Author: David White, WN5Y