Troubleshooting Your Radio Equipment
Contents
1. in the cable If you ve followed all these steps and you still haven t discovered the problem it s time to get out your equipment manual and review the troubleshooting section This section gives possible causes for common symp toms It is important that you read and study it before you decide to open up your radio Use All Your Senses Don t be deterred by the difficulty of performing repairs on your own equipment Some problems that seem impossible to solve turn out to be simple to fix When the November 1993 65 0000 mm ma Voltage ma Current Digital VOM Connector A is mn Voltage w Current Digital VOM Connector B Fig 1 A volt ohm meter VOM can be used to check for defective cables A reading of zero resistance indicates a short A An infinite resistance reading indicates an open circuit B With this particular meter a 1 on the far left side of the display indicates infinite resistance When measuring from the center conductor to the shield a good coaxial cable should show infinite resistance open If the meter indicates a short check the connector controls of my 2 meter hand held stopped working I was prepared for an expensive repair bill The radio failed to respond to the controls I couldn t enter frequency or change the mode Surely the microprocessor had failed I opened the radio to determine if I could replace the chip While inspecting the circuit board2. in the equipment At the first sign of trouble do the follow ing Q Check the positions of all the operating controls Q Check all of the mode indications and verify the mode Q Check all the cables and connections of your equipment Eliminate the Operator First Most problems can be easily solved by examining the controls For example you turn on your radio but don t hear audio Check the audio gain control Is it turned down Is the squelch turned up so that the audio output is muted Don t laugh When this happened to me the first time I was stumped until I took a look at the squelch setting Another common operator error involves transmitting CW with the transceiver set to the SSB mode When you try to transmit nothing happens This problem is easily identified by referring to the mode indicator Sometimes the source of this problem is not obvious For example some radios have a control lock button that disables the front panel controls If this button is pressed by mistake the radio appears to be unrespon sive to any commands because it is When checking your control settings be sure to include your cables and accessories Suppose you turn on your transceiver and tune across the band without hearing a single signal Is the band dead Tuning to another band you discover that it s dead also This makes you suspicious and you begin to think that your receiver has failed Well maybe not Troubleshoo
3. I noticed that a small metallic particle was shorting two of the printed circuit traces When I removed it the radio worked per fectly The moral of the story is Carefully in spect your radio After you open the case look for short circuits loose or broken con nections and burned components Smell is as important as sight Smell your radio for burned components Look for burned spots or evidence of arcing Take your time You never know what you may find To Fix or Not to Fix Once you ve completed your inspection you need to decide whether to take your radio to arepair shop At this stage you should read the troubleshooting section of the ARRL Handbook It will give you ideas on how to troubleshoot your equipment Call the manufacturer s service department or a re pair shop that specializes in your brand of radio and see if they have a simple cure Some problems can be diagnosed over the phone Ask if this is a problem that occurs frequently because of a design deficiency in the transceiver If the technician thinks that the problem can be fixed be sure to get a cost estimate As an additional precaution get a second opinion Call another repair shop and compare the results of the two estimates After you obtain the repair estimates consider the following Were the technicians 66 OS confident that the problem could be fixed for a reasonable cost Were the technicians familiar with a similar problem that they had
4. Troubleshooting Your Radio Equipment By Harry Ricker KC3MX 34 Cross Ridge Court Germantown MD 20874 ou awake one Saturday morning eager to check into your favorite net But when you turn on the radio nothing happens This is the moment that all hams dread Your equipment doesn t work and you have visions of expensive repair bills and several weeks or months off the air You desperately hope that nothing serious is wrong But remembering that terrific thunderstorm last Thursday evening it becomes clear that your radio has been hit by lightning All those sensitive integrated circuits must be blown up Great you think I can t hear any thing even with the volume turned all the way up My receiver is blown for sure When this happened to me I was certain that my 1000 solid state radio was badly damaged However by using basic trouble shooting methods I determined that the problem was a short in the microphone con nector that had locked the radio in transmit mode The problem was easily fixed at no cost Something like this is going to happen to you It s inevitable When it does you need to apply sound principles of equipment troubleshooting before you decide to turn your rig over to a radio shop Most equip ment problems are caused by operator error and defective cables and connectors When equipment is sent to the shop for repair the technician may not be able to fix it because the failure was not
5. e a series of blunders Opening up the case I began looking for damaged compo nents Using my VOM I discovered a short circuit between the power supply terminals of the radio I tried to test the power supply protection diode It indicated a short to ground Convinced that the diode was bad I attempted to remove it from the circuit Dur ing this process I broke the diode After an hour J managed to remove the broken diode and install a replacement I reconnected the radio and it still didn t work I had missed something but what Stop ping to think for the first time I decided to recheck the fuse It was bad Even though the fuse looked good a resistance check with my VOM showed an open circuit The broken fuse wire was hidden by the cap at the end of the fuse A new fuse solved the problem The problem was simple a blown fuse I violated my own troubleshooting rules by thinking that the failure was in the radio and I was wrong However my primary error was not stopping to think clearly I just as sumed that the fuse was good because it looked good But panic clouded my judg ment and I magnified a simple blown fuse into a major repair operation Harry Ricker KC3MX became a ham at age 15 Amateur Radio was the inspiration that led to an electrical engineering career in satellite communi cations Harry holds an Extra Class license and is an active operator on HF QRP and 6 meters He teaches Amateur Radio license classe
6. ivate it with your offset switched to 600 kHz above Always Check Your Cables and Connectors Seasoned hams know that the most fail ures occur in the cable and connectors Con nectors are especially vulnerable because they re constantly being connected and dis connected The first step after verifying your control settings is to check that the connectors are screwed in tightly When you encounter a high SWR or a low output power indication look for a loose connector first After you have checked for loose connec tors look for shorted or opened cables Shorts are often caused by poorly soldered connectors or crushed cables Open cables are usually caused by broken wires at the connector Use a VOM volt ohm meter to check your cables Disconnect both ends of the cable and remove it from the equipment Don tassume that the cable is not connected to ashort circuit Remove the cable Switch the meter to the resistance scale 2000 ohms full scale or less and measure the resistance between the center pin of the coaxial con nector and the shield If a short circuit is present the resistance will be nearly zero see Fig 1 If the cable isn t shorted you re not out of the woods yet You need to check for an opened cable Connect your VOM between the center pins of both connectors Then connect your VOM between the outer shells of both connectors The resistance should be zero in both cases If itisn t you have a break
7. repairs first and the high cost repairs last For example if your tube type radio has low output power it s reasonable to suspect the final amplifier tubes Don t rush to buy new ones though Arrange to have a friend lend you his tubes and see if that fixes the problem Check the suspect tubes on a tube tester Be sure to check the driver tube too Once you ve veri fied that you need new tubes then it s time to get out your checkbook Clear Thinking is Important It is very easy to get into trouble when attempting to repair your own equipment Clear thinking is the most important trouble shooting tool you have Don t hurry to fix the problem This is always disastrous Hurry causes panic which prevents clear thinking Before you dig into the problem plan a course of action Read your equipment manual and the troubleshooting section of the ARRL Handbook to refresh your memory The following story shows how panic can magnify a small problem into a big problem I connected my 2 meter all mode trans ceiver to a power supply with the wrong polarity Of course the radio didn t work Discovering my mistake I corrected the polarity but the radio still didn t work Swearing at myself for gross stupidity I was sure that I had destroyed my expensive radio Panic and anxiety took over I des perately needed to fix the problem I visually checked the fuse and it looked good Because I was in a panic I proceeded to mak
8. s sponsored by the Montgomery Country Amateur Radio Club ger
9. successfully repaired Finally consider if the problem is something simple that you can fix yourself If the repair estimate is high consider troubleshooting it yourself at least to the point where you can verify that the problem is not a simple low cost repair But if you don t have a good grasp of elec tronics and you don t know someone who does send the radio to the shop Three Ironies of Troubleshooting Troubleshooting is a process of eliminat ing the possible failures one by one It is ironic because most of the time the culprit is not what you expect The First Irony Whenever you are ab solutely certain that you have correctly guessed the cause of a failure you will be wrong This is my primary rule for troubleshoot ing When you ve deduced the cause of fail ure you also need to think about the cost of being wrong The Second Irony Whenever you be lieve that an expensive hard to find com ponent is the cause of your failure you will be wrong In other words you should check and replace the inexpensive components first before you attempt to replace the expensive parts The Third Irony The amount of effort required to replace acomponent is inversely proportional to the probability that it has failed Putting it another way don t go after the hard to replace components until you elimi nate all other possibilities If you decide to fix the equipment your self make the simple low cost
10. ting your radio equipment is easier than you think If you follow these troubleshooting techniques you ll be able to solve most problems yourself without the cost of expensive repairs First verify that the antenna is connected If this doesn t reveal the problem check all your cables and connectors to make sure they re hooked up correctly If you have an antenna switch is it in the correct position If you have an antenna tuner check to see that it s tuned to the correct band A tuner acts like a filter If your transceiver is tuned to 10 meters but your tuner is set for 80 meters your tuner attenuates the 10 meter signals Finally be sure to check the attenu ator setting on your rig I operated during a contest once with my 20 dB attenuator switched on I couldn t understand why the band conditions were so poor By the time I discovered my error the contest was over When operating VHF FM via a repeater verify that your controls are set properly before transmitting If you fail to access a repeater when using an H T low battery volt age may be the culprit Most H Ts provide a low battery indicator Check this first If the repeater requires a CTCSS tone to acti vate is your CTCSS function switched on Is the correct tone selected Make sure the repeater offset is set to the proper value This is a very common problem If the repeater is listening 600 kHz below the output fre quency you can t act
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