Troubleshooting - Elenco Electronics AK-100/SP-1A Assembly And Instruction Manual

TROUBLESHOOTING

If any parts are missing or damaged, see instructor
or bookstore. DO NOT contact your place of
purchase as they will not be able to help you.
Contact Elenco Electronics (address/phone/e-mail
®
is at the back of this manual).
If you are experiencing a problem, first read the
theory of operation to familiarize yourself with the
operation.
Component Check
1. Be sure that all components have been mounted
in their correct places.
2. Make sure that C1 and C2, the electrolytic
capacitor is mounted correctly. The negative lead
should be in the hole as shown on the top legend.
3. Have LED's LED1 and LED2 been installed
correctly? The flat side of their bodies should be
in the same direction as marked on the top
legend. If the LED's are in backwards, they will
not light.
4. Pay close attention to the red and black wires of
the battery snap. The red wire should be installed
in the positive (+) hole and the black wire in the
negative (–) hole. Snap in a fresh 9-volt battery.
DESOLDERING PRACTICE/COMPONENT REPLACEMENT
In this exercise you will replace the 22kΩ resistors
R4 and R6 with two 56kΩ resistors. You unsolder the
resistors using the solder wick and then install new
resistors.
1. Remove the battery from the battery snap.
2. Locate the pads that resistor R4 is soldered to.
3. Place the solder wick on one of the pads and the
iron on top of it (refer to page 8).
4. As the solder melts, it will be drawn into the wick.
Problems
1. No LED's Light
• Check the solder connections for the battery
wires and switch.
• Check that all parts are in the correct way.
2. LED1 Does Not Light
• Check C1, LED1 and Q1.
3. LED2 Does Not Light
• Check C2, LED2 and Q2.
4. LED1 or LED2 is Always On
• Check C1 and C2 for opens.
• Check Q1 and Q2 for shorts.
Remember that there are two oscillators. If no sound
comes out of the speaker, but the LED flashes
alternately, then the 555 timer is not working. Be
sure that the volume control is at maximum. Check
the components IC1, R5, R8, R9, C3, C4 and C5. Be
sure that the IC is in properly.
If a steady sound (not wobbling) comes out of the
speaker, then the multivibrator is not working. Check
the components associated with transistor Q1 and
Q2. Check the LED by shorting the transistor
collector to the emitter. The LED should light. If not,
then the LED is either open or backward.
5. When the iron and wick are removed, the solder
should be removed.
process if some solder remains.
6. Unsolder the other lead and remove then remove
the resistor.
7. Follow the same procedure and remove resistor R6.
Now use the resistors R4A and R6A mounted on the
component card, and install them on the PC board.
Reconnect the battery and the kit should oscillate at
the correct frequency.
-13-
You need to repeat the