ANALOG MULTIMETER KIT MODEL M-1250K Assembly and Instruction Manual Elenco Electronics, Inc. ® Copyright © 2007, 2000 by Elenco® Electronics, Inc. All rights reserved. Revised 2007 REV-H No part of this book shall be reproduced by any means; electronic, photocopying, or otherwise without written permission from the publisher.
PARTS LIST If you are a student, and any parts are missing or damaged, please see instructor or bookstore. If you purchased this kit from a distributor, catalog, etc., please contact Elenco® Electronics (address/phone/email is at the back of this manual) for additional assistance, if needed. DO NOT contact your place of purchase as they will not be able to help you. RESISTORS Qty.
Qty. 2 1 2 Symbol Value D1, D2 Q2 Q1, Q3 2CZ A1015 C1815 SEMICONDUCTORS Description Diode Transistor Transistor Part # 314148 321015 321815 MISCELLANEOUS Qty. * * * * * Description Part # 1 PC Board 516001 1 Fuse 0.5A, 250V 533004 2 1.
CONSTRUCTION Introduction board so that good solder flow will occur. Be sure that the lead extends through the solder smoothly indicating a good solder joint. Use only rosin core solder. DO NOT USE ACID CORE SOLDER! Do not blob the solder over the lead because this can result in a cold solder joint. Assembly of your M-1250 Analog Multimeter Kit will prove to be an exciting project and give you much satisfaction and personal achievement.
ASSEMBLE COMPONENTS TO THE PC BOARD After each step, put a check in the box located next to the step that you have completed. Place the PC board on a table with the copper side facing up and insert the four input sockets into the PC board holes as shown in Figure A. Solder the input sockets to the PC board as shown in Figure A. Apply enough heat to allow the solder to flow around the input socket. Insert the six transistor sockets into the PC board as shown in Figure 1 and then solder into place.
ASSEMBLE COMPONENTS TO THE PC BOARD After each step, put a check in the box located next to the step that you have completed. C3 - .047μF Discap (473) R29 - 820kΩ 1% 1/4W Resistor (gray-red-black-orange-brown) Q1 - C1815 Transistor (see Figure C) R30 - 260kΩ 1% 1/4W Resistor (red-blue-black-orange-brown) R8 - 680Ω Potentiometer (see Figure E) R26 - 31kΩ 1% 1/4W Resistor (orange-brown-black-red-brown) R7 - 240Ω 1% 1/4W Resistor (red-yellow-black-black-brown) C1 - .047μF 400V (473) Mylar Cap.
ASSEMBLE COMPONENTS TO THE PC BOARD After each step, put a check in the box located next to the step that you have completed. R28 - 3MΩ 1% 1/2W Resistor (orange-black-black-yellow-brown) C4 - .001μF (102) Capacitor D1 - 2CZ Diode (see Figure D) R24 - 10kΩ Potentiometer (see Figure H) 2.5” Violet Wire (tin both ends) Jumper Wire (see Figure I) R27 - 4.5Ω 1% 1/4W Resistor (yellow-green-black-silver-brown) R22 - 18.
ASSEMBLE THE BUZZER Tin the buzzer in the three locations shown in Figure Ka. Tin both ends of the 3.5” red, white, and green wires as shown in Figure Kb. Solder the red, white, and green wires to the buzzer (see Figure Kc). Place the buzzer into the holder and snap together (see Figure L). Figure Kb Tin Buzzer Solder Wire Soldering Iron Red Wire White Wire Figure Ka Green Wire Figure L Figure Kc SOLDER BUZZER AND BATTERY CLIP WIRES TO PC BOARD Solder the red buzzer wire to point R on the PC board.
SOLDER METER MOVEMENT WIRES TO PC BOARD Tin the ends of the meter wires. Solder the red meter wire to M+ and the black wire to M– on the foil side of the PC board (see Figure N).
INSTALL BATTERY CLIPS Install the PC board into the case (see Figure O). Align the buzzer holder over the two posts and press it down in place (see Figure O). Install the two single and one double battery clip as shown in Figure O. Solder the red and white wires from the PC board locations 3V+ and 3V– to the single battery contacts (see Figure P). Solder the red and yellow wires from the PC board locations 9V+ and 9V– to the single battery contacts (see Figure P).
CALIBRATION Batteries Install the following parts: 1. Install the 9V and the two 1.5V (AA) batteries as shown in Figure 1. Be sure to observe the polarity markings on the bottom of the battery compartment. 2. Place the thumb wheel knob onto the 0Ω ADJ pot located at the lower right side of the meter dial. Meter Calibration (See Operating and Testing the Multimeter Section for meter operating instructions). 1. Before starting tests, set the meter needle to zero .
INSTALL BACK COVER AND 0Ω ADJ KNOB Install the bottom case and mount into place with an M4 x 10 screw as shown in Figure Q. Place the 0Ω ADJ knob onto the front of the unit on the upper right of the panel.
TROUBLESHOOTING CHART This chart lists the condition and possible causes of several malfunctions. If a particular part is mentioned as a possible cause, check that part to see if it was installed correctly. Also, check that part and the parts connected to it for good solder connections. PROBLEM POSSIBLE CAUSE No DC voltage reading Refer to Figure 2 for a better understanding of how the meter works. 1. Check for open fuse. 2. Check resistors R1 - R8, R13 for correct values and good solder connections. 3.
OPERATING AND TESTING THE MULTIMETER CAUTION: When measuring an unknown voltage or current, always start with the range switch set to the highest scale. Then, if necessary, move the range switch down until the meter reads in the middle or right half of the dial. Checking your multimeter for proper operation is fairly easy. Of prime importance is knowing which scale is read for each setting of the range switch. DC voltage is read on the dial immediately below the meter mirror.
AC Voltage Test In reading AC voltage, it is necessary to obtain a known source of AC. A 12 volt transformer is preferred. If one is not available, use the 120VAC line. CAUTION: Be very careful when working with 120VAC. Be sure that the range switch is in the 250 or 1000VAC position before connecting the test leads to 120VAC. 1) Plug the red test lead into the + socket, and the black lead into the –COM socket. 2) Set the range switch to the appropriate ACV position.
Buzzer Test 1. Set the range switch to the BUZZ position. 2. The buzzer will sound if there are 20Ω or less across the leads. DCV (NULL) Test 1. 2. 3. 4. Set the range switch to either the ± 5 or ±25 scale in the DCV (NULL) position. Adjust the 0Ω ADJ pot for a zero center position Plug the red test lead into the positive (+) socket and the black test lead into the –COM socket. Connect voltage to the test leads and read the voltage.
AC Voltage Measurement Figure 5 shows a simplified diagram of the AC voltage measuring circuit. Two diodes are added to the series resistors to rectify the AC voltage. The input impedance on the AC voltage ranges is 9kΩ per volt. On the 250VAC range, the input impedance is therefore 2MΩ. Figure 5 DC Current Measurement Figure 6 shows a simplified diagram of the DC current measuring circuit. Here the resistors are placed across the meter to shunt the current.
hFE Measurement Figure 8 shows a simplified diagram of the hFE measuring circuit for PNP transistor. Here the range switch is in the X10 ohms position and the transistor circuit takes the place of the external resistor in the ohms measurement. The higher the hFE of the transistor, the more current flows in the external circuit and the lower the effective resistance. The meter reads this resistance and the hFE of the transistor may be read on the hFE scale.
-18- ECB Pin-out 2SC1815 2SA1015 SCHEMATIC DIAGRAM M-1250K
Elenco® Electronics, Inc. 150 Carpenter Avenue Wheeling, IL 60090 (847) 541-3800 Web site: www.elenco.com e-mail: elenco@elenco.
