30
Troubleshooting
Below are some problems that have been reported and solutions. If you still have a problem, I am always available by
email at
and the newly formed LP-100 Yahoo Group is available at
http://groups.yahoo.com/group/LP-100/
For excessive current, always check for solder bridges and proper orientation of ICs first. If a step calls for more than one IC to be
added and current is excessive, remove the ICs and re-install one-by-one until you narrow the source of the high current.
Problem
Suggested solution
No +5 VDC at Initial Checkout Step 1.
Check wiring of U2 and D5, and that the white-striped wire on the
power cord is connected to the + lead of the supply.
Excessive current at Initial Checkout Step 1.
Check for proper polarity on D5.
Excessive current at Initial Checkout Step 2.
Check for proper placement of U7 and U3 (PIC).
Improper display at Initial Checkout Step 2.
Check setting of R8 to make sure the contrast is in range. Check
that Y1 is soldered properly. Check that the PLED cable is
installed properly. If all this checks out, the PIC firmware may be
bad. Try flashing with the latest firmware on the LP-100-Updates
page.
Excessive current at Initial Checkout Step 3.
Check for proper placement of the added ICs.
Incorrect operation of buttons.
Check for good ground lead connection on three tactile switches.
Incorrect values for RSSI or Temp.
Check U5 & U8 for proper orientation. Check output voltage of U5
at pin 6. It should be very close to 2.500 V. Check for proper
orientation of U7 for Temp. Check soldering around U9 for RSSI.
Excessive current at Initial Checkout Step 4.
Check the added jumper between U4 pins 7&8 to make sure it is
not touching ground (on ser #s 1-100 only). Check R39 and C42
for proper wiring.
Power reading is erratic
Make sure C37 wasn’t installed. This part is shown on the silk-
screening, but was deleted before production along with 4 other
parts. This is covered in the Overview paragraph at the top of the
Assembly section. Also, make sure that the standoff on coupler
xfmr T2 is firmly bolted down and that the short wire is also solidly
attached. Make sure that the two BNC connectors on the
controller PCB are soldered properly.
Frequency counter is not registering the correct band
Check U9 by looking at the RSSI voltage on the Reference CAL
screen. It should vary with applied RF power. Normal voltages are
~0.400V at 5W, ~0.660V at 100W. Also check the wiring of T2,
and make sure the enamel has been removed from the wires, and
that the wires are properly soldered to the pads.
Temperature is not being displayed
Check that U7 is installed properly. Remember, the silk-screening
is backwards for this part on serial #s 1-100.
Summary of Contents for LP-100
Page 28: ...28 Schematic Page 1 ...
Page 29: ...29 Schematic Page 2 Coupler Schematic ...
Page 36: ...36 Appendix A ...
