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GE 90-30 PLCs Most Common Problem & How to Prevent It

August 4, 2017
90-30 plcOne of the most common problems we see at Qualitrol with 90-30 machines is CPU and power failures. Regularly checking your diagnostic fault tables can help you catch issues before they become larger problems. Although fatal fault errors are obvious when they happen, other problems may be less noticeable until they get worse and impair system operation. Keeping your PLC running is of the utmost importance on your factory floor. When you have a legacy system such as the 90-30 series from GE, understanding how to handle these common problems can help immensely. So what can you do to prevent power failures in your 90-30 system? Here’s how and what you can do to prevent it and diagnose the problem after it’s happened.

Check Your LEDs

The first place to start is checking your LEDs when it comes to locating the source of the problem with your 90-30 PLC. These will be on the front of your power supply. There are four LEDs to check—PWR, OK, RUN, and BATT. Here’s how to tell the health of each of these indicators with the help of your diagnostic fault tables. PWR. The Power LED is indicative of your power supply. When the light is green, your supply is in good standing. If there’s no light at all, you’ll need a battery to keep the program running while you change the power supply. Since the 90-30 has eight distinct modules for power supply, you’ll need to consult the diagnostic fault tables to determine which one is causing the problem. We’ll talk about how to do that in this post. This LED is all about your CPU health. If the LED is green, it’s working. If the LED is out, you’ll need to replace the CPU. This is a problem that’s likely the result of a hardware failure in your CPU module. Your 90-30 has 17 different CPU modules, so you’ll need to check the fault tables identify which one is responsible for the outage. RUN. This light is indicative of the status of your CPU—when it’s running properly, the LED is on. If the LED is not on, this means there’s been an error that’s stopping your CPU from running. You’ll need to consult the fault tables to learn why. It’s worth noting that if you have failed I/O devices, this will not affect the run status of your CPU and you’ll need to look elsewhere to fix this problem. BATT. This is one LED that should not be lit up if your battery is working properly. If the light is red, however, your battery needs to be replaced. You can and should do this while the PLC is on. Install the new battery before you remove the failed battery; there will be two connectors for this purpose. Don’t worry about losing your program; the 90-30 has a backup battery so your PLC will still operate without the failing one.

Utilize Diagnostic Fault Tables

The two fault tables you need to be concerned with are those for I/O and for the CPU. The diagnostic fault tables contain detailed information about what went wrong. Utilize them to your best advantage! This includes the rack and slot position of the module that’s failed. There will also be a time and date on the problem, indicating how long the issue has been happening. You can resolve the problem and then clear the fault tables. The diagnostic fault tables are a great tool in order to conduct preventative maintenance as well as to get to the root of major problems. Remember, although an LED indicator may not tell you when something’s wrong, the fault tables always reveal the true status of your hardware.

Update and Back Up Your PLC Program

If a power failure were to happen, would you lose your program? Updating your program as regularly as you’re able to—or anytime changes are made—is a good idea. In the event that your battery should fail for any reason, you’ll know a copy of your program is safe. When you have an older system like the 90-30 many times no changes are made to the system until there’s a problem. As a result of this, programs can be lost as soon as the power fails if the backup battery is faulty. Replacing the old battery before you unplug it is essential—90-30s run on a backup battery so losing your program isn’t likely, but why risk it?

Reach Out for PLC Support

Since GE’s 90-30 is a system that’s already reached the end of its life, you won’t be able to turn to GE for support of your system. Fortunately, Qualitrol has the expert support you need. Our team of professionals have decades of combined experience in handling 90-30 systems. When it comes to legacy PLCs, we not only have the talent to solve your problem, we have the resources you need including parts, repairs, and more. You can prevent power failures with your 90-30 CPU by following the above tasks. It’s simple, efficient, and most of all, protects your machinery. If you have any questions about your 90-30 system, we invite you to get in touch. Your problem solving experts are closer than you think! 90-30 plc support  
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