NHRC-2 User Guide
NHRC-2 Troubleshooting Guide
Page 1
3/16/2000
Copyright © 2000, NHRC LLC
All Rights Reserved.
NHRC-2 Repeater Controller
Troubleshooting Guide
Rev D PCB Only
Power-related problems
Check all of your solder joints carefully. A poorly soldered or an
unsoldered joint can cause all sorts of problems. Solder joints should
appear bright and shiny, and the solder should taper from the end of the
pin to the pad on the board; there should not be a "blob" of solder on the
pin. Make sure that there are no solder "bridges" between pads or traces.
It is very easy to create solder bridges between the IC pins; these pins are
only 1/10 inch apart.
Apply power with all the chips removed from their sockets and an
ammeter in series with the +12 volts (pin 2 of P1 on the controller). There
should be an extremely small amount of current flowing into the board
with the IC's removed, typically less than 5mA. If there is more current,
check component placement, and ensure that there are no solder bridges
on the board. Remove the ammeter, and re-apply power. With all of the
chips still removed, check for +5 volts at pin 3 of U4 (LM7805), pin 14 of
U1 (PIC16F84), pin 28 of U2 (ISD1420), and pin 18 of U3 (M8870). If
any of the power supply voltages are not right do not insert the chips
until this problem is found and corrected.
Make sure the PIC16F84 is in the correct socket on the board. The M8870
sits in the socket nearest to the crystal. Make sure the chips are plugged in
correctly, with pin 1 corresponding with the square pad on the PCB.
Improper installation of the chips can destroy them! If you had any of the
chips in backward they may be “nuked”.
CAS Signal problems
The easiest way to verify correct operation of the CAS signal is to remove
ISO1 (4N36) from its socket, and plug a LED in instead. The LED's
anode (the "+" leg, usually longer) goes into pin 1, and the cathode
(the "-" leg, usually shorter) goes to pin 2 of the socket. If you are unsure
of which leg of the LED is which, test it with +12 volts and a 1Kohm
resistor in series with the LED. When the CAS signal is correctly applied,
the LED should glow. A dim glow is probably OK. If the LED lights up
very brightly, or “smokes”, it is likely that the CAS signal's voltage is too
