11.
Troubleshooting and Repair
“I noticing that the TJ2B receive sound is not as loud. So I took the back cover off and
when I touch the board and depress, it becomes loud again.”
This is caused by two possible reseasons on the main board:
1) Cold solder of T1, T2, T3. Please check the pads with the amplifying glass. Solder the
miniature transformers with the help of the amplifying glass. Use thick books as the holder
to adjust the distance between the PCB and amplifying glass.
2) A broken coupling SMD cap (The cap cracks between the body and the metal part).
The SMD cap might be broken by bending or twisting force in transportation or in the
process of assembling the main board into the enclosure. There will be a thin crack
between the cap body and the metal part. They are C1, C2, C5, C14. C2 is the most
possible because it is close to the mounding hole. Try to locate the broken cap with an
antenna. Use the antenna center conductor in series with a 0.01 cap (alternatively use a
long wire) to touch C14. First right side pad and then left side. A loud noise or broadcast
will be heard, indicating IF AMP module and C14 are working. Move the antenna to C13,
the same level will be heard. Move to C9, the sound should be much smaller, because of
the XTL filter. Move to C5, the sound level should be the same as C9. Move to collector of
Q1(the heat sink), same level as C5. The above tests indicate all the coupling caps are
good. Now move to the right pad of C2 (base of Q1),sound should be louder than the
collector due to the amplification of Q1. Move to the left side of C2, should be the same
level; otherwise the cap is broken. Now move to the right side of C1. Noise or signal will
be heard. Now the left side of C1. The same level as the right side of C1; otherwise the
cap is broken. The crack might be found with the amplifying glass to save the above
process.
12. Calibrating DDS unit and BFO with your frequency counter
1) Select proper channel
Usually the frequence counter has two channels: Channel 1
for measuring frequency
ranging from 10Hz - 100MHz. This channel is sub-divided into two ranges: 10Hz - 10MHz,
the reading not scaled. 10MHz - 100MHz, the reading scaled; Channel 2 for measuring
frequency ranging from 100MHz - 1000MHz, the reading usually
scaled. For our
purpose 10Hz - 10MHz in CH1 is suggested, because the reading is not scaled (More
precise and in reality it handles frequencies up to 15MHz) and reading in "Hz" can be
observed.
Summary of Contents for TJ2B
Page 3: ...Cables for internal connections Components package...
Page 5: ...Pre assembled Miniature Transformers Packed in a separate plastic bag Brass Stand Off Parts...
Page 10: ...How to insert the LCD Cable Never bend the cable end soldered to the LCD...
Page 12: ...Now solder the 7 wire cable...
Page 35: ...50 ohm cable and MIC cable are connected How the cable is soldered...
