Ramsey Electronics UAM4 Manual page 27

difficult to determine if the correct value is in the correct place. While it is
not an absolute indication, a comparison of the size of each capacitor with
respect to others of the same value may reveal a placement error.
Generally the larger the value of the capacitor the larger the component.
There are only 4 values of non polarized capacitors in this kit - the 1uF
devices, C1, C2, C3, C4 and C10 will be the largest. C9 is smaller, and
C7, C11, C15, and C16 are smaller than C9. Finally, C8 should be the
smallest.
Make sure all the other capacitors are installed in the correct direction.
These are electrolytic capacitors, meaning they have a voltage polarity
requirement. The marked band on one side of the capacitor indicates the
positive side, so use this to make sure they are oriented correctly.
The Zener diode, D2 and transistor Q1 look very similar. Refer to the
parts list for the markings on these components and make sure they are
installed in the correct locations.
There is a 7.5 volt regulated voltage generated on the UAM4 board. This
is done with the circuit consisting of zener diode D1, capacitor C17 and
resistor R7. If there is no output, check, to see if the 7.5 volts is present.
Connect a multimeter negative lead to the UAM4 ground and check the
voltage on pin 3 of jumpers H1, H2, H4, H5, H6, H7 and H8. If you find
there is more than +7.5 VDC on these pins, or no voltage at all, there is a
problem with D2, C17, or R7. Check to make sure these components are
installed correctly.
If you don't see anything wrong the next step is to check for shorted and
open connections using a multimeter set to measure resistance. Using a
magnifying glass and very fine probes (a straight pin connected to the
meter using clip leads works great) check for any connection between
adjacent components and between traces that are near each other. (Be
very careful when checking with the pin - some of the traces on the UAM4
board are so small that a simple poke with a pin could actually break
them!) The best way to check between traces is to find a place that has
exposed conductor (silver in color) on the trace and connect the meter
leads between the points of interest. The green color on the board is
called a solder mask and helps prevent solder bridges between
components and traces. It is best to avoid damage to the mask. When
probing, look for readings that are very low, near zero ohms. If a reading
is higher than a few ohms the chances are that it is OK and caused by the
various components in the circuit.
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