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PROBLEM:
D1 lights but I don't get any indications from one or more of the sections
Measure the voltage / resistance at the following points.
NOTE! The next voltage is measured with the black lead connected
to the "virtual" ground between R22 & R23.
WRONG MEASUREMENT(s)?
(or if everything looks right but it still doesn't work)
This may be a tough one because there are a number of things
that could be going on. You may find the following procedures
helpful.
How to troubleshoot the detector and amplifier sections.
Because the problem may be caused by a weak signal or a detec-
tor/amplifier problem and we are working with very small signals
we will do some very basic checks with a simple multimeter. We'll
refer to the 315MHz section for this discussion but the steps apply
to all sections of the WCT3, just refer to the schematic and trans-
late the references to match the applicable section.
NOTE! The next voltage is measured with the black lead connected
to the "virtual" ground between R22 & R23.
With push button S1 activated, measure the voltage at U1 pin
"+" connection of the battery , [+8.5V to +9.1V].
Connection between R22 and R23 , [+4.5V to +5.2V].
U1 & U2 pin 4, [+8.5V to +9.1V]
U1 & U2 pin 11, [0VDC]
With out pressing pushbutton S1 measure the resistance at
U1 & U2 pin 11, [0 ohms].
With out pressing pushbutton S1 measure the resistance at
U1 & U2 pin 4, [1.7K ohms].
Measure the voltage on the "+" lead of the comparator section
of U2 for the section with the problem. For example U2 pin 3
if the 315MHz section is the problem. [The reading should be
within +/- 20mV of the reading indicated on the schematic.]
1 and activate and deactivate the 315MHz signal. The read-
ing should change between a level lower than 1300mV with-
out a signal and over 1300mV when activated.
WCT3 29
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