Step 11: Troubleshooting Overview

Fully test the system

This post is part of a series describing the generic, high-level troubleshooting process.

Previous Posts:
What is Troubleshooting?
Simplified Troubleshooting Overview
Step 1. Understand the correct inputs and outputs of the “black box.”
Step 2. Determine which output(s) are incorrect.
Step 3. Figure out which input(s) affect that output(s).
Step 4. Verify that those inputs are as expected.
Step 5. Analyze the path(s) from input(s) to output(s).
Step 6. Check all connections.
Step 7. What are the devices in those path(s) that change the data?
Step 8. Eliminate the devices that could not cause this output.
Step 9. Test the remaining devices.
Step 10. Repair/Replace faulty device(s).

Step 11. Fully test the system.
Now that all of the issues are (hopefully) fixed, the entire system needs to be fully tested.

Test every condition, every input combination. Do not skip anything. It is possible that your “fix” caused other issues, or even that there were more issues than you found the first time around.

If everything is not working properly, start over at step 1 and repair the newly found issues. Take into account that the work that you did could have caused the new problem(s). This could help you find the issue more quickly.

This is the final post in this series. Hopefully it was helpful for you.

Step 10: Troubleshooting Overview

Repair/Replace faulty device(s).

This post is part of a series describing the generic, high-level troubleshooting process.

Previous Posts:
What is Troubleshooting?
Simplified Troubleshooting Overview
Step 1. Understand the correct inputs and outputs of the “black box.”
Step 2. Determine which output(s) are incorrect.
Step 3. Figure out which input(s) affect that output(s).
Step 4. Verify that those inputs are as expected.
Step 5. Analyze the path(s) from input(s) to output(s).
Step 6. Check all connections.
Step 7. What are the devices in those path(s) that change the data?
Step 8. Eliminate the devices that could not cause this output.
Step 9. Test the remaining devices.

Next Post:
Step 11. Fully test the system

Step 10. Repair/Replace faulty device(s).
Once you locate a device(s) that is causing a problem, you need to repair or replace it. Which you choose depends on many factors, such as: time available, replacement availability, complexity (or possibility) of repair, cost, etc.

Whichever you choose, in the end, the malfunctioning device needs to become a properly functioning device(s).

Repeat this for each device found to be faulty. It’s a good idea to test that part of the system after fixing the device. Test in the same way that you did to find that the device had an issue.

In the next step, we will test the system as a whole.

Step 9: Troubleshooting Overview

Test the remaining devices.

This post is part of a series describing the generic, high-level troubleshooting process.

Previous Posts:
What is Troubleshooting?
Simplified Troubleshooting Overview
Step 1. Understand the correct inputs and outputs of the “black box.”
Step 2. Determine which output(s) are incorrect.
Step 3. Figure out which input(s) affect that output(s).
Step 4. Verify that those inputs are as expected.
Step 5. Analyze the path(s) from input(s) to output(s).
Step 6. Check all connections.
Step 7. What are the devices in those path(s) that change the data?
Step 8. Eliminate the devices that could not cause this output.

Next Posts:
Step 10. Repair/Replace faulty device(s).
Step 11. Fully test the system.

Step 9. Test the remaining devices.
In this step, we will basically repeat all of the steps, just on a smaller scale.

If the device is simple, like a switch or relay, you will run through the steps fast. What is the resistance with the contacts closed? What is the resistance with the contacts open? Do the contacts open and close?

If the device is complicated, like a PLC, circuit board, IC, etc., you will need to treat this item like a new “black box” and go through all of the steps. This is where it can get complicated. You could save a lot of time by “throwing parts at it”… If a spare is available, replace it. If it fixes the problem, you can decide if you will just leave the spare in place, or fix the original. If it doesn’t fix the issue, just put the original back in, and move on the the next item.

If you need to troubleshoot and/or repair an item like a circuit board, the same steps apply, but it is much more difficult and is well beyond the scope of the high-level blog.

Test each device, one at a time, until you find the faulty component(s).

The Importance of Quality Passwords

Imagine a world world without passwords. Wouldn’t that be amazing? We didn’t have them back before computers and the internet, and in the future everything will have secure password-less login everywhere, but for now we need them if we are going to use the world wide web.


  • Why does everything require a username and password?
  • Can’t I just use the same password for everything?
  • But why do passwords need to be so complicated?
  • How am I supposed to remember all of these passwords?

These are questions that everyone has asked at some point. In this post, I plan to answer those questions, and hopefully give you a better understanding of the importance of good passwords and adding additional security measures.

Nothing is unhackable

First, you need to know is that NOTHING is unhackable. Anyone who tells you different is either lying or doesn’t understand how things work. To better understand why, you only need to realize that to stop a hacker, the security needs to be 100% secure 100% of the time. A hacker only needs to be successful once.

That doesn’t even account for Social Engineering. Social Engineering is, basically, tricking someone into giving you the information that you want. Spam emails and phone calls are the most common examples of this. If you can talk someone into giving you access to a computer or bank account, there is no amount of security that can keep them out. If you give a thief the keys to your house, it won’t matter how good your locks are, they’ll still get in.

NEVER give this information to anyone.

The Convenience <—–> Security spectrum

Security and convenience are inversely related. The more security that you have, the less convenient it is to use. This is a simple fact. For example, If you were to put five deadbolts on your front door, your security would increase, but it’s less convenient to lock and unlock five locks. If you key each lock differently, your security would increase even more, and the convenience would decrease yet again by having to use five keys.

You will need to decide where on the spectrum you want to live, and this can be different based on the account. You might be willing to sacrifice more convenience to better secure your financial accounts than you are for facebook. I can’t tell you if this is right or wrong, it’s your choice based on your threat tolerance.

Just remember, the easier it is for you, the easier it is for the bad guys.

Why does everything require a username and password?

Your username distinguishes you from every other user. The password is an attempt to ensure that you are the only one that can log into your account. I say “attempt” because it does not do a very good job of keeping others out who want in bad enough.

Can’t I just use the same password for everything?

Using the same username and password for multiple accounts is the most convenient and least secure method. I consider this basically zero security. Never do this.

Even the best companies eventually get hacked into. Usually when that happens, one of the first things that a hacker looks for is a list of usernames and passwords. Every website is supposed to store passwords as a “hash”, not the password itself, but hashes are able to be converted back into the password (It’s not easy, but is possible), and not everyone hashes passwords.

A password hash is the result of processing the password through a cryptographic function. When you enter your password into a website, it preforms the same cryptographic function on what you entered and compares the output to the stored hash. Hashes are easy to calculate but very difficult to reverse.

If a website that you don’t even use anymore gets hacked and they get your username and password, no big deal right? Who cares about the information on that site? Maybe so, but what if it is the same login that you still use for your bank account? What if one of the many hackers that purchase your login information give it a try on your bank’s website? And what if they transfer all of your money into their own account? Is it still “no big deal?”

But why do passwords need to be so complicated?

Two of the many ways that hackers attempt to gain access to someone’s accounts are “Brute Force” and “Dictionary Attacks.”

With a Dictionary Attack, the hacker will use software to guess the password, using words from a dictionary. Then they will add numbers to the end and replace letters with numbers and special characters. This type of attack can be very fast when the password is not random.

  • password
  • Password
  • password1
  • password123
  • pa$$w0rd
  • pa$$w0rd123

These are some of the first ones in the dictionary. Why? Because they are some of the most commonly used passwords. These, and similar could be cracked in less than a second by this attack.

In a Brute Force attack, a hacker will also use software, but this time they will try every combination of characters in the hope that they will be able to find the correct combination. If successful, they will have access to the account. A long and complicated password will make this harder for them. Imagine how long it would take to brute force the password 123456 vs. B$G+i|KC(u92kG:h0 Which is more secure?

Password length matters as well as its randomness. The random password E9Uwl$ can be cracked within two minutes, while B$G+i|KC(u92kG:h0 could take 317,098 years to crack by brute force.

Below are some examples of random passwords of different lengths to demonstrate how increasing the length of your passwords makes them much harder to crack.

LengthExampleEst. Time to Crack# of Possible Combinations
6E9Uwl$2 minutes689,869,781,056
8Pq:O8uyR3 hours6,095,689,385,410,820
10%Q)^9^^j6b12 days53,861,511,409,490,000,000
12m|%y+=Z1:2Iv3 years475,920,314,814,253,000,000,000
13jJ6Rj!enJ/}5(32 years44,736,509,592,539,800,000,000,000
14iN%Sso.H%M3A*x317 years4,205,231,901,698,740,000,000,000,000
18Ag{Civ-9pDVv[{6it$367,834 years328,323,043,381,012,000,000,000,000,000,000,000
217!^FY!e,)$@/S^qQxXV9q3 billion years272,699,866,663,574,000,000,000,000,000,000,000,000,000
How am I supposed to remember all of these passwords?

Not on a piece of paper. Writing them down is not secure, and tends to make you choose passwords that are easy to write. This makes them less secure. Plus, if someone steals that paper, or takes a picture of it, they have ALL of your logins.

This is where Password Managers come in. They are a safer way to store all your account logins in one place. This database of usernames and passwords is encrypted with a single password to decrypt all of them. With a password manager, you will only need to remember one password.

There are many options out there offering different levels of security and convenience. Some are free, some are paid, and some offer both. A few examples are:

  • Apple Keychain
  • Google Password Manager
  • bitwarden
  • LastPass
  • 1Password
  • NordPass
  • KeePassXC
  • and many more.

Most will also offer a random password generator which is very helpful in creating quality passwords. Some store your database online for ease of use and access across devices, some store it only on your local hard drive for higher security. They will also have browser plugins which will allow you to easily save a password to the manager when it’s created, as well as to automatically fill in your username and password when you go to a website.

What else can I do to become more secure?

Okay, so I’ve changed all of my passwords to be unique and stored them in a good Password Manager. It was a lot of work, but wasn’t all that hard. Is there anything else that I should do to be even more secure?

If you want to take your security to the next level, you should add Two Factor Authentication (2FA) to all accounts that offer it. There are several types of 2FA.

The overarching term is Multi-Factor Authentication (MFA), when the quantity of factors is two (such as username/password and TOTP), it is typically referred to as 2FA.
e-mail/SMS OTP 2FA

With e-mail or SMS One Time Passcode (OTP) 2FA, when you successfully enter your username and password into a website, it will send you a text message or e-mail with an OTP that you must enter before the login will complete. This is a more secure than not using 2FA, but if your e-mail or cellphone are hacked, the hacker can receive your OTP.

TOTP 2FA

Time-based One Time Passcode (TOTP) is a more secure version of OTP. This used to be done exclusively with hardware tokens, but software is primarily used now. This software will generate an OTP for your specific account that is only valid for a limited time, typically 30 seconds. This code will need to be entered after your username and password before it times out. TOTP is more secure than e-mail/SMS OTP because of the short time it is valid, and the fact that the code is generated on your device and is not sent over e-mail or text message.

Some password managers include TOTP and there are also standalone apps.

Security Key 2FA

Beyond the scope of this post is hardware security keys, such as the yubico YubiKey. The YubiKey offers TOTP as well as password-less login on some sites.

There’s More

This was just a high level overview. There is a lot more information available elsewhere online.

Step 8: Troubleshooting Overview

Eliminate the devices that could not cause this output.

This post is part of a series describing the generic, high-level troubleshooting process.

Previous Posts:
What is Troubleshooting?
Simplified Troubleshooting Overview
Step 1. Understand the correct inputs and outputs of the “black box.”
Step 2. Determine which output(s) are incorrect.
Step 3. Figure out which input(s) affect that output(s).
Step 4. Verify that those inputs are as expected.
Step 5. Analyze the path(s) from input(s) to output(s).
Step 6. Check all connections.
Step 7. What are the devices in those path(s) that change the data?

Next Posts:
Step 9. Test the remaining devices.
Step 10. Repair/Replace faulty device(s).
Step 11. Fully test the system.

Step 8. Eliminate the devices that could not cause this output.
In the last step, we determined everything that could change the data in the path that is having issues. In this step, we will eliminate any of those that could NOT cause the issue that we are seeing.

It is very possible that you will not be able to eliminate anything at all. Be very conservative in the things that you eliminate, if you are not, you may eliminate the item that is the problem. Just because it shouldn’t be able to cause that, doesn’t mean that it can’t.

Some possibilities are:

  • If the output voltage is higher than the input voltage, it’s probably not an issue with a connector, switch, relay, or wire (unless there’s a short). If the output voltage is lower than the input, it very much could be one of these.
  • I started a bullet list, but I really can’t think of anything else that would apply in most situations. There may be more in your situation.

Step 7: Troubleshooting Overview

What are the devices in those path(s) that change the data?

This post is part of a series describing the generic, high-level troubleshooting process.

Previous Posts:
What is Troubleshooting?
Simplified Troubleshooting Overview
Step 1. Understand the correct inputs and outputs of the “black box.”
Step 2. Determine which output(s) are incorrect.
Step 3. Figure out which input(s) affect that output(s).
Step 4. Verify that those inputs are as expected.
Step 5. Analyze the path(s) from input(s) to output(s).
Step 6. Check all connections.

Next Posts:
Step 8. Eliminate the devices that could not cause this output.
Step 9. Test the remaining devices.
Step 10. Repair/Replace faulty device(s).
Step 11. Fully test the system.

Step 7. What are the devices in those path(s) that change the data?
What are all of the items between input and output that have the ability to change the data? What are the “black dots” referenced in Step 3? Are there relays, PLCs, ICs, circuit boards, processors, etc.?

Make note each item, what it is, where it is in the path (what is before and after it), and any visible defects. If the item appears broken, go ahead and skip to Step 9 and test or replace that item. If it fixes everything, great! If not, come back here and pick up where you left off.

And Don’t forget that connections (connectors and splices) can change the data too. See Step 6.

I recently worked on a system in an automobile that hadn’t worked in years. When I got to Step 6, I found a large connector on the back of the fuse box that had the automotive style lever to lock the connector in place, and it just didn’t look right. Upon closer inspection, I found that the lever wasn’t properly engaged on the tabs. The bottom of the connector was seated, but the top was not. For the system that I was troubleshooting, the contacts were just barely touching. Without a load, you would read 12V, when you turned the system on, it would drop to 0V. I removed the connector and reinstalled it properly, and like magic, the system worked perfectly. My client was expecting the repair to take all day, I had it working in 2 or 3 hours after walking in the door.

Tech Handyman

In order to fill our time between contracts, Crider Consulting is pleased to announce a new service for the non-tech consumer.

Do you or a loved one struggle setting up new devices or learning how to use them? Give Crider Consulting a call to schedule an In-Home appointment and we’ll do the hard work for you.

We are available for in-home setup and/or support of many types of devices. Nothing is too small.

  • Computer Setup
  • Printer Install
  • WiFi Setup
  • Cell Phone Setup
  • TV Remote Programming
  • Streaming Device Install & Setup
  • Robot Vacuum Setup
  • Training on how to use devices
  • And More

Serving Rockingham and surrounding counties in Virginia.

https://crider-consulting.com/thm

Step 6: Troubleshooting Overview

Check all connections.

This post is part of a series describing the generic, high-level troubleshooting process. Side effects include, frustration, annoyance, hair pulling, possible bad language, and thinking out-loud.

Previous Posts:
What is Troubleshooting?
Simplified Troubleshooting Overview
Step 1. Understand the correct inputs and outputs of the “black box.”
Step 2. Determine which output(s) are incorrect.
Step 3. Figure out which input(s) affect that output(s).
Step 4. Verify that those inputs are as expected.
Step 5. Analyze the path(s) from input(s) to output(s).

Next Posts:
Step 7. What are the devices in those path(s) that change the data?
Step 8. Eliminate the devices that could not cause this output.
Step 9. Test the remaining devices.
Step 10. Repair/Replace faulty device(s).
Step 11. Fully test the system.

Step 6. Check all connections.
”The Jim Sweet patented swiping action.” That’s what we called it in one of my previous lives, where I learned this “trick” of disconnecting and reconnecting connectors. Contacts in connectors will build up corrosion which can completely stop equipment from working. Sometimes it is the obvious, everything is green or white, level of corrosion, sometimes it is so little (maybe a piece of dust) that simply disconnecting and reconnecting a connector will dislodge the problem and fix everything. Sometimes a little contact cleaner will do the trick. Other times you will need to replace contacts or entire connectors to get rid of the bad connection.

I can’t tell you how many times that I have taken something apart looking for a problem, not found one, given up and put it back together, and like magic… it works perfectly. When this happens, it is both satisfying and annoying. I like to know what fixed it just as much as I like it to be fixed. Often what fixed it is like the number of licks to the center of a Tootsie Pop, “The world may never know.”

Whenever possible, disconnect every connector in the path (one at a time) looking for corrosion, broken wires, recessed pins, bad crimps on contacts, anything that is not right. Also take a look at any splices and replace any that are suspect. Fix or replace anything that you find in this step. Whether you find anything or not, its a good idea to put everything back together and test it again. You might have fixed it without knowing and you can buy a bag of Tootsie Pops to celebrate.

Step 5: Troubleshooting Overview

Analyze the path(s) from input(s) to output(s).

This post is part of a series describing the generic, high-level troubleshooting process. These statements have not been evaluated by the FDA.

Previous Posts:
What is Troubleshooting?
Simplified Troubleshooting Overview
Step 1. Understand the correct inputs and outputs of the “black box.”
Step 2. Determine which output(s) are incorrect.
Step 3. Figure out which input(s) affect that output(s).
Step 4. Verify that those inputs are as expected.

Next Posts:
Step 6. Check all connections.
Step 7. What are the devices in those path(s) that change the data?
Step 8. Eliminate the devices that could not cause this output.
Step 9. Test the remaining devices.
Step 10. Repair/Replace faulty device(s).
Step 11. Fully test the system.

Step 5. Analyze the path(s) from input(s) to output(s).
Now that you have determined that you are looking at the right equipment (even if it is not where you started), you understand what the inputs and outputs should look like, deduced which outputs are not correct, know which inputs affect those outputs, verified that the inputs are as expected… its time to do a deeper dive into the inner workings of the equipment.

This step is a more detailed version of Step 3. If you didn’t have schematics, wiring diagrams, or other documentation in Step 3, you’ve probably already done this step. If you had paperwork, now is the time to physically look at the electron flow and see the routes, wires, switches, relays, circuits, pneumatics, motors, fuses, and everything else between input and output inside the actual equipment.

What is the path? What does it go through? Go back and read Step 3 if needed. At this step, we still don’t need to know what the “dots” do, we just need to see everything for ourselves. It is much easier if you learn the path and see what it looks like before you dive into the following steps.

Step 4: Troubleshooting Overview

Verify that those inputs are as expected.

This post is part of a series describing the generic, high-level troubleshooting process. Do not use if you are allergic to troubleshooting, blogs, or learning.

Previous Posts:
What is Troubleshooting?
Simplified Troubleshooting Overview
Step 1. Understand the correct inputs and outputs of the “black box.”
Step 2. Determine which output(s) are incorrect.
Step 3. Figure out which input(s) affect that output(s).

Next Posts:
Step 5. Analyze the path(s) from input(s) to output(s).
Step 6. Check all connections.
Step 7. What are the devices in those path(s) that change the data?
Step 8. Eliminate the devices that could not cause this output.
Step 9. Test the remaining devices.
Step 10. Repair/Replace faulty device(s).
Step 11. Fully test the system.

Step 4. Verify that those inputs are as expected.
In this step, we verify that the inputs to the system are correct. If you find an input that is not as expected, then maybe the issue is upstream of this equipment, or there is no issue at all. It is not unusual to find the the problem is:

  • Not a problem
    • Someone had an input set wrong
    • There was a misunderstanding of how it is supposed to work
  • In a completely different box
    • An upstream output is wrong, giving this box a wrong input
    • A downstream input has an issue affecting the output of this box (as discussed in Step 2)

You need to do everything that you can to verify that the issue is actually with the equipment that you are analyzing. If you don’t you could waste time troubleshooting in the wrong place. If you realize that the issue is in another box, move your analysis to the other box, and start over at Step 1. Only once you have personally verified that the inputs are correct, the output is incorrect, and the issue it not downstream, can you actually say that there is an actual issue with the equipment that you are troubleshooting.