Author Topic: Problem Determination Exercise  (Read 1539 times)

Offline Smurf Hunter

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Problem Determination Exercise
« on: February 17, 2017, 02:24:13 PM »
The follow was from a presentation in my city's Emergency Comms Teams meeting.  I've removed any personal/private details, but thought folks here might be interested...

Problem determination/problem source identification involves an investigation following a logical progression through a complex system. The investigation may involve observation, tests, and measurements, to pinpoint the failure.

Try to understand exactly what is going on. Try to capture the most information that you can. Any information, as trivial as it could appear, could give you the hint for determination of the source of the problem.
Check the obvious things first.

Questions you need to ask:

  • Did it ever work correctly before?
  • What does proper operation look like?
  • When did the problem appear the first time?
  • What has been changed recently?
  • Can the problem be re-created?

Take measurements, or preform tests to help narrow down the failing domain.
  • What parts are working correctly?
  • Don’t assume anything, test it!
  • If there is not an obvious point of failure, choose a reasonable starting point and either work forward or backward to the failure point.

What tools do you have available to help test your station?

  • Multimeter
  • SWR Meter
  • Oscilloscope
  • Another radio

The following scenarios will present a problem for which we will try to determine the cause. There may be multiple failures that could cause the same symptoms, but you will have to determine the failure the leader had in mind (these are all taken from real problems the leader has experienced). You may ask the leader questions to try and isolate the cause, including measurements at various points, but you must be specific on what you ask for (eg. “what is the voltage measured at the power supply output terminals”). Use a logical progression, and any virtual tools you can think of. The diagram on the next slide is the station setup that will be used for each scenario.



Scenario 1
Sunday night you head to your base station to check in on the weekly net. You push the power button on the front of the radio like always, but this time nothing happens. The lights on the radio do not come on, and you don’t hear any stations talking.

Scenario 2
Sunday night you head to your base station to check in on the weekly net. You power up the radio and tune to the repeater channel. You do not hear the Net Control station, or any other stations talking. You put out a call for anyone, but there is no response.

Scenario 3
Sunday night you head to your base station to check in on the weekly net. You power up the radio and tune to the repeater channel. You hear the Net Control station, and  other stations talking, but they sound distorted and are hard to understand. When you check in, NCS says you are loud and clear.

Scenario 4
Sunday night you head to your base station to check in on the weekly net. You power up the radio and hear the Net Control station, and  other stations talking, all loud and clear. When you check in, NCS says you were garbled at the beginning of your transmission, but then cleared up at the end.

Scenario 5
Sunday night you head to your base station to check in on the weekly net. You power up the radio, set to the repeater channel, and hear the Net Control station, and  other stations talking, all loud and clear. When you try to check in, your radio appears to power off, but then comes back on. Net control says he heard a brief transmission, but could not identify it. You try again, and the same thing happens.

Scenario 6
Sunday night you head to your base station to check in on the weekly net. You power up the radio, set the repeater channel, and hear the Net Control station, and  other stations talking, all loud and clear. When you try to check in, you hear a “pop” somewhere in the house, and your radio goes dark. Your spouse yells “what was that?”

Scenario 7
Sunday night you head to your base station to check in on the weekly net. You power up the radio and hear the Net Control station, and  other stations talking, all loud and clear. When you check in, NCS says “last station, no audio” and calls your station again. You try again, and NCS says the same thing and then moves on in the roll call.

Scenario 8
Sunday night you head to your base station to check in on the weekly net. You power up the radio and hear the Net Control station, and  other stations talking, all loud and clear. When you check in, NCS does not acknowledge your call and moves on in the roll call. When NCS calls for late or missed, you attempt to check in, watching your radio, which indicates it is transmitting. Again, NCS does not acknowledge your call.

Scenario 9
Monitoring your base station, set to the repeater channel, you hear one of the local stations come on looking for someone to chat with. Her signal is very noisy. You reply to her call, and she reports that your signal is also very noisy.

Scenario 10
Sunday night you head to your base station to check in on the weekly net. You power up the radio and set it to the repeater channel. You smell something like burning electronic components. Your dog starts barking, and your spouse says “what is that awful smell?”

Offline Carl

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Re: Problem Determination Exercise
« Reply #1 on: February 17, 2017, 05:35:03 PM »
Gremlins.  Really good locic exercise...thanks.