MFT-20 DSB Transceiver Kit
Page 26
IF YOUR KIT DOES NOT WORK AFTER ASSEMBLY
Don't worry, it is not uncommon that a kit doesn't work on the first try; stay calm, as in most cases they
are minor problems with a simple fix.
Most of faults are due to poorly soldered connections or misplaced components; it is very rare to find a
faulty component. Before taking any measurements with test equipment, check all the connections and
carefully inspect your soldering, looking for cold joints, short circuits between traces, sockets not making
good contact, or components mounted in the wrong place.
If your kit does not work after final assembly, please follow these steps in order:
- Double-check every step in the assembly manual, the solder connections, and correct component
placement.
- If you have access to instrumentation, take measurements and follow the signal path of the circuits to
diagnose what is happening and why.
- Request another ham experienced with kits or a radio technician to check your work. Someone taking a
fresh look may find things that you overlooked.
- If you decide that technical assistance is needed, you are welcome to send an email to
. As a last resource, you may send the kit in for repair; however, I will have to charge
for any repairs done, although I will try to keep the cost as moderate as possible.
To help troubleshoot your transceiver, the following voltage table may be useful. The IC and transistor
voltages were measured in receive
(without volume)
and transmit
(without modulation)
. If there is a
fault, it is quite likely that one or more of the readings will be very different.
IC Ref.
Type
Pin1 RX
Pin1 TX
Pin2 RX
Pin2 TX
Pin3 RX
Pin3 TX
Pin4 RX
Pin4 TX
IC1
NE603
1.38
0
1.30
0
0
0
4.75
0
IC2
UA741
0
0
6.75
0
6.75
0
0
0
IC3
LM386
1.38
1.38
0
0
0
0
0
0
IC4
78L06
6V out
0V out
IC6
NE602
1.05
1.05
1.05
1.05
0
0
4.99
4.99
IC7
78L06
6V out
6V out
IC8
78L08
0V out
8V out
IC Ref.
Type
Pin5 RX
Pin5 TX
Pin6 RX
Pin6 TX
Pin7 RX
Pin7 TX
Pin8 RX
Pin8 TX
IC1
NE602
4.77
0
5.87
0
5.12
0
5.92
0
IC2
UA741
0
0
6.73
0
13.37
0
0
0
IC3
LM386
6.63
6.63
13.40
13.25
6.69
6.61
1.39
1.39
IC6
NE602
4.99
4.99
5.83
5.83
5.13
5.13
5.91
5.91
Q Ref.
Type
B Rx
B Tx
E Rx
E Tx
C Rx
C Tx
Q1
BC547
0
0.70
0
0
0
0
Q2
BC547
3.74
3.90
4.89
4.80
7.90
7.90
Q3
PN2222
0
1.53
0
092
0
12.36
Q4
BD135
0
2.30
0
1.70
13.42
13.48
Q6
2SC2078
0
0.65
0
0
13.42
13.48