Bringing faulty Tecnoware UPS to new life

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If you own the Tecnoware UPS ERA Plus 750, maintaining it regularly will ensure continuous power backup. In this guide, I’ll show you how to replace the battery with an official Tecnoware replacement, while also addressing a common issue caused by faulty MOSFETs and capacitors. We’ll replace the MOSFETs (specifically the IRLB8314, designed for UPS devices), and I’ll also guide you on how to test these components using a multimeter.

Disclaimer

This guide involves working with electrical components, which can be dangerous if not handled properly. Always follow proper safety precautions, including unplugging the device and allowing time for stored charge to dissipate before working on the unit. The steps provided here may void your UPS warranty. The author cannot be held responsible for any damage to equipment, property, or personal injury that may result from following the procedures outlined in this article. Proceed at your own risk.

Tools and Materials Needed

• Replacement Tecnoware UPS battery 12V 5A , Faston 6.3 mm , Size 90 x 100 x 70 mm
• New MOSFETs (IRLB8314 Power MOSFETs)
• New capacitor 16V 1000uF
• Screwdrivers (Phillips and flathead)
• Soldering iron and solder
• Wire cutters/strippers
• Multimeter (with diode test functionality)
• Insulating tape or heat shrink tubing (optional)

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Step 1: Safety First

Before starting, ensure your safety:

• Disconnect the UPS from the mains and any connected devices.
• Wait at least 15 minutes after unplugging to ensure any residual charge is dissipated.
• Use insulated gloves if possible while handling electrical components, I’m using these ActiveArmr from Ansell.

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Step 2: Open the UPS Case

1. Turn the UPS upside down and locate the screws securing the case (usually Phillips-head screws at the bottom).
2. Remove the screws and carefully open the case. Some internal components may still be connected to the top half, so open it gently.
3. Use a flathead screwdriver if necessary to pry the cover open.

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Step 3: Replacing the Battery

1. Locate the battery inside the UPS. It’s usually the largest component. This specific UPS contains a 12v 5A battery mounted to lay on a side.
2. Disconnect the battery terminals by pulling off the red (positive) and black (negative) connectors.
3. Remove the old battery by sliding it out.
4. Install the new battery. Attach the red wire to the positive terminal (+) and the black wire to the negative terminal (-). In my case I had to replace two batteries from two different UPS of the same type, I decided to opt for the Tecnoware battery I found on amazon at a very reasonable price, much expensive of others, but I had bad experiences with the cheaper one.

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Step 4: Identifying and Replacing Faulty MOSFETs and Capacitors

If your UPS has been showing issues like failing to switch to battery mode or overheating, it could be due to faulty MOSFETs or capacitors.

Locating the MOSFETs and Capacitor:

1. Find the 4 MOSFETs. In this model it’s particularly easy as the have NO heat sink at all… the MOSFETs are IRLB8314, specifically designed for UPS applications.
2. The capacitor will likely be nearby, recognizable by its cylindrical shape. Look for any visible damage such as bulging, leakage, or discoloration. The capacitor is right between to of the four MOSFETs and it’s black in color

Replacing and testing the old MOSFETs:

1. Desolder the faulty MOSFETs by heating their solder joints with a soldering iron.
2. Carefully remove the old MOSFETs and insert the new ones, ensuring they’re in the correct orientation.
3. Solder the new MOSFETs into place, ensuring solid connections without cold joints (dull-looking solder).
4. To test if they are still operative, look at the Step 5 where I explain the process in detail

Replacing the Capacitor:

1. Desolder the old capacitor by heating its solder points and gently pulling it out.
2. Insert the new capacitor, making sure to align it according to the correct polarity (positive and negative markings are on the PCB).
3. Solder the capacitor in place, then trim any excess wire from its leads.
4. You could recover some capacitor of this type from old power supply unit for personal computer, like I’ve done.

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Step 5: Testing the MOSFETs Using a Multimeter

Before reassembling the UPS, it’s crucial to test the new MOSFETs to ensure they’re working properly. You can test a power MOSFET using a common multimeter with a diode test functionality. If you do not already have a multimeter with the required functionality, you could appreciate this one from KAIWEETS on amazon that thanks to a limited offer is available at a very reasonable price, today, October 24th, 2024.

How to Test a Power MOSFET with a Multimeter:

1. Set your multimeter to diode test mode (indicated by a diode symbol).
2. Identify the MOSFET pins: Most MOSFETs, including the IRLB8314, have three pins: Gate (G), Drain (D), and Source (S). Look at the datasheet or the component’s labeling to confirm which pin is which.

• Pin 1: Gate (G)
• Pin 2: Drain (D)
• Pin 3: Source (S)

1. Testing Gate-to-Source (G-S):

• Place the multimeter’s positive probe on the Source (S) and the negative probe on the Gate (G).
• The multimeter should show no continuity (OL or open line). If there is continuity, the MOSFET is faulty.
• This specific MOSFET, just like other power MOSFETs, has a diode between SOURCE and DRAIN

1. Testing Drain-to-Source (D-S):

• Keep the positive probe on the Source (S) and place the negative probe on the Drain (D).
• The multimeter should show a low voltage drop (typically around 0.5V to 0.7V). If the reading is very high or zero, the MOSFET could be faulty.

1. Charge the Gate:

• Now touch the positive probe to the Gate (G) and the negative probe to the Source (S). This will charge the MOSFET’s gate.
• After doing this, check continuity between the Drain and Source again by placing the negative probe on the Drain and the positive on the Source.
• The multimeter should now show continuity (a low voltage drop). This indicates that the MOSFET is turning on correctly.

1. Discharge the Gate:

• Finally, discharge the Gate by touching the Source and Gate pins together with a metal object (such as tweezers).
• Retest the Drain-to-Source. It should now show no continuity again, indicating the MOSFET has turned off properly.

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Step 6: Reassembly

1. Inspect all connections to ensure the components are soldered correctly.
2. If the UPS keeps beeping after you reconnect the battery or after you press the start button, something is still not working thus disconnect the battery immediately and check every single step.
3. Close the UPS case by aligning the cover and reinserting the screws.
4. Tighten all screws to secure the case firmly.

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Step 7: Testing the UPS

1. Reconnect the UPS to power and allow it to charge for several hours.
2. To test the functionality, plug in a device and unplug the UPS from the wall. The UPS should switch to battery mode seamlessly, and the device should remain powered.

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Conclusion

By replacing the battery, MOSFETs, and capacitor in your Tecnoware UPS ERA Plus 750, you’ve significantly extended its lifespan. Testing the MOSFETs using a multimeter ensures you’ve correctly installed components that are essential for power regulation. With proper care and regular maintenance, your UPS will continue to provide reliable protection for your electronics during power outages.

If you have any questions or run into trouble while making repairs, feel free to drop a comment below.