©1996 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a registered trademark. Revised: 1/19/00
- Page 5 -
REPAIR.
The only special repair procedure
is replacement of a damaged ic. Be-
cause it is a surface mount device,
conventional desoldering techniques
may not remove enough solder to al-
low removal. If you know for sure that
the ic is dead, it is simpler and it
protects the pc board from damage if
you use a fine pair of cutters to cut
each lead of the ic at the edge of the
package. Then, unsolder and remove
one lead at a time. After that, it is
relatively easy to use a vacuum desol-
dering tool or Solder Wick to remove
any excess solder prior to installing a
new ic. Refer to the assembly in-
structions for information on orienta-
tion of the ic.
PARTS LIST.
Ref # Value (marking)
C1-C2
0.1 µf monolithic
C3
2.2 uf electrolytic
C4
0.1 µf monolithic
C5
2.2 uf electrolytic
C6
0.1 µf monolithic
C7
2.2 uf electrolytic
C8
18 pf ceramic NP0
C9
33 pf ceramic NP0
D1-D2
1N4148 diode
Q1
2N3904 NPN xstr
R1
10K resistor
R2
20K trim pot.
R3
10K resistor
R4
3.9 meg resistor
R5-R6
2 meg resistor
S1
7 pos. DIP switch
U1
MX465DW ic
U2
78L05 5V regulator ic
Y1
4.000 MHz crystal
Table 2. U1 Test Voltages
Pin#
Function
Test Voltage
1
V
DD
+5V
2
Oscillator
7V p-p @ 4 MHz
3
Oscillator
5V p-p @ 4 MHz
4
Load/Latch
+5V
11
V
SS
0V
12
Comparator Ref
+3.2V
13
RX Decode **
+5V no tone, 0V tone
14
Comparator In ** +4.2V tone, 0 no tone
15
RX Detect **
+5V tone, 0V no tone
16
Tone Out ‡
2.2V p-p tone
19
RX Out
+2.5V
20
TX Out
+2.5V
21
Bias Bypass
+2.5V
22
TX In
+2.3V
23,24
RX AF In
+2.5V
** Receive Mode Only
‡ Transmit Mode Only
