115v

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1. Line - Voltage Checks
Measuring voltages is usually the next step in troubleshooting malfunctioning appliances. To avoid replacing expensive components by mistake, these measurements should be as accurate as possible. The first consideration is the line-voltage level available to the appliance. When factories list check voltages for their appliances, they specify the operating voltages under which these results were obtained. Thus, it's important to have some means of determining whether the line-voltage level is within a range sufficient for accurate readings. Line voltage refers to the main power-line voltage supplied to the home from the community power source. This power has been standardized country-wide at 115V, but variations in the load level on a line will produce fluctuations ranging anywhere from as low as 108V to as high as 125V. During the summer months especially, these irregularities are frequent as the power demands of air-conditioning equipment exceed the utility companies' ability to supply them without reducing voltage levels. These line fluctuations affect the readings obtained during appliance tests.
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2. Variable AC Power Supply
Not only is it important to know what the line voltage is, but it is helpful to have some way of compensating for any fluctuations. For this purpose, a variable ac power supply can serve the repairman well. This device features a metered knob for adjusting output to the voltage required (normally 0- 140V). A receptacle mounted on the side to take a standard three-prong plug allows direct connection to an appliance without the inconvenience of screw terminals. Thus, whatever the level of the line voltage is, it can be adjusted to a 115V Output suitable for making voltage checks of appliances in accord with factory specifications.
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3. Variable-Frequency AC Power Supply
Occasionally you will want to test European appliances for their performance. Since most equipment from abroad will not operate as intended from standard American 60 Hz 115V outlets, a special power supply is needed for this task. This involves considerable expense which can be avoided by building a variable-frequency ac power supply. This device can produce the 50 Hz output at 115-120V for which most European appliances are designed, as well as provide the 400 Hz output necessary for many power tools. The key component in the circuit is an audio-frequency oscillator with a range of 0-400 Hz (Eico makes a kit suitable for this purpose) whose output is coupled by shielded cable to an audio amplifier. The amplified signal at 72W across 8 ohms places 24V ac across the secondary winding of the 120-24V stepdown transformer. When a load is connected to J (a standard European two-prong receptacle), 120V is induced into the primary. Adjustment of the audio-frequency oscillator to 50 Hz and of the volume control on the audio amplifier for 115-120V output (indicated on voltmeter V) creates the necessary power for foreign equipment.
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4. Ground Checker
An appliance contained in a plastic housing and which has no exposed metal parts should not be dangerous to handle from the standpoint of electrical shock. On the other hand, a portable power tool such as an electric drill can be dangerous to handle, especially if the user is standing on a moist surface or touches a grounded object, unless the metal case of the tool is grounded through a three-prong power plug. It is now standard practice to equip hand tools with three-wire cords terminated in three-prong safety plugs. Power is transmitted through two of the prongs and two of the wires. The third prong is connected to ground through the electric outlet and its wire is connected to the metal frame of the tool. When there is no three-slot 115V outlet available, the tool can only be connected to the power line through a two-prong to three-prong adapter. The adapter has a pigtail lead which is supposed to be connected to the screw that secures the outlet faceplate. If the outlet box (and faceplate) are actually rounded, the tool case is grounded, making it safe to use. However, when the device has a two-prong plug, it may be dangerous to use if it has ail internal ground. Consider the circuitry of a ground checker that can be assembled in a small minibox. It consists of a small 120V lamp, a DPST toggle switch, a three-hole 115V receptacle (Jl), a Fahnstock clip or binding post (J2), and a two-wire power cable equipped with a standard two-prong plug (P). One side of the 115V ac power line is grounded (by the power company) and the other side of the line is "hot" with respect to ground. To use the ground checker, the appliance is plugged into Jl which will accept either a two-prong or three-prong plug. With P plugged into an ac outlet, either terminal X or Y of Jl will be grounded through the power line, depending upon which way P is plugged into the outlet. When checking an appliance or tool that has a three-prong safety plug, flip switch S from one position to the other. If the third wire of the power cable is connected internally to the metal case of the device, lamp I should light when S is in one position, but not in the other. When checking a device that has a two-prong power plug, connect J2 to the metal case of the device (or other exposed metal part) through a clip lead. The lamp should not light when set to either position. If the lamp does light, there is an internal ground in the device.
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5. Electric Rotisserie
In this category fall many of the broiler / baker / toaster ovens now on the market. Electrically these units consist of a thermostat and one or two heating elements. Some of them contain a motor to rotate a spit as well. The rotisserie may encompasses a timer in addition to a thermostat and two heating elements. You should note that all current must pass through the timer—hence the timer must be on in order for any portion of the rotisserie to function. A bake button controls the lower element and a grill button controls the upper element. A rotis button operates the drive motor and upper element, and the temperature knob controls the thermostat. Consider a unit rated at 115V, 1500W. it draws 1200W on the lower element and 1350W on the upper element. Begin by making an operational test. Remove the griddle and tray so that the elements can be observed. Place an oven thermometer on the rack in the center of the oven. Then close the front and lid doors. Turn the timer on and engage the bake button. Set the temperature control knob to 300°F. The indicator light should go on to indicate power to the element. When the light goes off, the cycle is completed. After several cycles, the temperature reading should be between 275° and 320°F. There can be an overshoot of 100° on the first cycle. If an adjustment is required, turn the control knob to the correct temperature range, loosen the set screw in the knob, and position the knob at 300°F. As a double-check, make an additional temperature test at 450°F. To disassemble, pull or pry off the timer knob. Then loosen the set screw and remove temperature control knob. The nameplate is secured by a screw located under the timer knob. Take out the screw securing the thermostat to the side panel. It is located on the right side of the temperature control shaft. Remove the 5 screws holding the left side panel to the chassis. Pry the panel off from the back so as to slide off the temperature control shaft in the front. The Hoover rotisserie employs a manual timer with an electrical switch. The switch can be tested with an ohmmeter, or it can be eliminated from the circuit by bypassing it with a jumper wire. The drive motor in the rotisserie shown (and in many others) is replaced as a unit. This motor should not require any additional lubricant. If a lubricant is added it must have a high temperature range due to the heat from the oven. Use one of the silicone greases in this area. To replace the thermostat, disconnect the lead wires and remove the thermostat from its mounting bracket. Save the old control shaft since it is not a part of the replacement thermostat. Install the thermostat with metal-to-metal contact on the mounting bracket. Mica washers are used behind the bracket. Place the control shaft into the thermostat. Calibration is now lost. Install the left side panel. With the timer on and the Bake button in, connect an ohmmeter or wattmeter to the cord. Turn the control shaft until the on-off positions are established. Then install the temperature control knob at the lowest setting and proceed with temperature test to calibrate the stat. The elements can be removed by disconnecting the wiring and sliding the elements off of their supports. Test with a wattmeter per specifications given above. Inspect the insulators for cracking, chipping, or other signs of deterioration, Hoover is a bit unusual since the company offers replacement chassis assemblies complete with sides, bottom, back panel, and all riveted parts. Most small-appliance makers do not supply major structural parts.
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6. Dehumidifiers
A humidifier adds moisture to the air, but a dehumidifier, on the other hand, takes moisture out of the air and converts it to water. Refer to Fig. 5-11. A compressor, similar to, but smidler than, those used in refrigerators forces gas under pressure into the coils. The gas causes the coils to become cold. A fan draws humid air from the room into the unit from the front and passes it over the cold coils. Moisture from this air condenses on the coils, and drips into a receptor. The diy air, after passing over the condenser coils, is returned to the room. The refrigeration unit is factory-sealed, and most manufacturers recommend that field servicing not be attempted. Instead, they suggest that it be returned to the factory for service. At certain temperature and humidity conditions frost may form on the cooling coil, but this will usually not harm the unit. A humidistat maintains the humidity at the desired setting. The receptor has a knockout plug for connection to a drain or hose. If the knockout plug is not used, an adjustable o erf low switch will stop the unit and turn the signal light on. The overflow switch is adjusted in this unit by the screw located under the receptor. Turning it clockwise will increase the water level in the receptor. Troubleshooting A wiring diagram for a Upical dehumidifier is shown at Fig. 5-12. To check the fan and motor, first remove the motor wires from the thermostat and starting relay. First make a resistance test, then test with 115V on lead wires. The motor can l>e removed and repaired, or, in the case of sealed units, replaced. The humidistat contains a tape which becomes longer or shorter relative to the moisture in the air and thereby operates the switch. Do not tamper with or attempt internal adjustments of the mechanism. To remove the humidistat, pull off the knob and remove the screws which secure the humidistat to the front panel. Catch any spacers between the humidistat and front panel. Test the electrical switch with an ohmmeter. The humidistat and switch are normally replaced as a unit. The overflow switch shown in the wiring diagram is normally closed between "common" and "NC." When depressed, "Common" to "NC" opens and "common" to "NO" closes. The thermostat located under the hood is a snap-action, normally closed thermostat opened by heat and used to stop the compressor. You should test it for continuity with an ohmmeter, but do not attempt to make any adjustments. The starting relay (located under the hood) is a current-operated relay used to start the motor. To test the assembly, pull the relay off of its terminals. Then: a. Test for continuity between the "run" terminal and the "common" of the relay. If open, replace the relay. b.   Connect a jumper between the compressor "run" terminal and the "run" terminal of the starting relay. c. Connect a voltmeter to the "start" terminal of the relay and the "common" terminal of thermostat. d. Turn the humidistat to its maximum pos tion. e.  Plug in the cord. If the relay is good, a click will be heard as the relay closes and full voltage will be indicated. f. A negative test means a defective relay or compressor. The compressor is a sealed unit. If defective, the complete dehumidifier must be returned to the factory. To test the compressor, connect an ohmmeter across the terminals of the compressor. The readings vary between makes and models, but should not exceed 15 ohms between any pair of terminals.
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