![]() ![]() Check for visual signs, and also use the multimeter Ohms range as well. ![]() One particular area can be the battery lead - these leads are particularly prone to damage as the need to be moved and if the battery has been replaced in a rough manner this could result in a lead being broken. With time and movement of the equipment, leads can become fractured. Check for any broken wiring that would prevent the power reaching the circuit board.To overcome this it can help to unplug and then re-mate the connector. One common problem is that connectors become corroded with time and connections can become very poor, especially of the equipment has not been used for some time. Its resistance should be less than an Ohm. Ideally remove the fuse and check for continuity with the multimeter. If a fuse is present, then it is worth checking tis.live and neutral, and either of these sides of the switch could be non-functional. Also remember that the switch may switch both sides on the incoming power, i.e. Then check for continuity across the switch, checking it on both on and off positions - use the Ohms range on the multimeter for this. This can be checked by disconnecting any power source - the power lead must be removed from the power to completely isolate the equipment. If the battery cannot supply the current required, then the voltage will fall as the radio is switched on. Check the voltage with the test meter when the radio is turned on. If the battery condition is not so obvious, then a simple voltage measurement using the test meter can highlight if this is an issue. Take care not to touch the residue as it can be corrosive The residue can cause the contacts to become corroded, so it is necessary to clean the contacts well. If this is the case remove the battery and clean any residue that may have leaked onto the battery holder and in particular the contacts. Sometimes it may be obvious as the battery may be leaking. If the multimeter indicates that there is no supply voltage then there can be a number of possibilities to investigate:īattery could be flat if the equipment is battery powered. Measure the voltage using a test meter at the points where the supply enters the circuit board. This is easily done using a multimeter set to a voltage range. They often arise from movement and physical damage, so it is often easy to find these faults and issues.Īccordingly the first step in any fault finding is to look for the major problems.Ĭheck the supply to the circuit: The first steps in checking the circuit are to ensure that it has power being supplied to it. This is one of the key stages in repairing any equipment.įortunately most faults with electronics equipment such as transistor radios are relatively easy to find - many are quite obvious and some may not even need any test equipment. The first step when looking at tracing any faults and testing a transistor circuit of any sort is to look for the obvious or major faults. High voltages can kill so be warned! Look for obvious faults Also, only the right test equipment, with the right certifications and capable of handling high voltages should be used where high voltages are present. Only qualified persons should attempt to repair mains powered equipment or equipment that contains high or hazardous voltages. Some electrical and electronics equipment may be mains powered. The test meter can be used to test these and often locate the fault very quickly.īoth analogue multimeters and digital multimeters can be used for these simple tests - the choice normally being made by what is available. However to use a multimeter to test a circuit and find faults it is necessary to have a little knowledge about the circuit, and also to adopt a logical approach in tracking down any faults that may exist.Ī little experience knowing the likely faults and failures that occur within the different types of equipment also helps. Multimeters are ideal items of test equipment for finding many faults in a transistor or other form of electronic circuit. One of the main uses for multimeters whether they are analogue multimeters or digital multimeters, DMMs is to test and fault find circuits like those in a transistor radio. Test meter basics Analogue multimeter How does an analogue multimeter work DMM digital multimeter How a DMM works DMM accuracy & resolution How to buy best digital multimeter How to use a multimeter Voltage measurement Current measurements Resistance measurements Diode & transistor test Fault finding transistor circuits Transistor Circuit Test & Fault Finding using a Multimeter Finding faults in transistor circuits with a multimeter can be simplified by adopting a logical approach along with using some hints and tips gained from experience.
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