Product Introduction
The TOSHIBA PU662 is a dedicated power supply unit designed for the T1 and T2 series of programmable logic controllers. It converts standard AC line voltage into the regulated DC power required for the backplane, ensuring stable operation for the CPU and all connected I/O modules. In my experience, this specific model is a common find in legacy system cabinets that have been running for decades.Its primary value lies in its dual-voltage output capability, providing both 5VDC for logic circuits and 24VDC for field devices or sensors. This design choice is actually clever, as it reduces the need for an external power supply for smaller I/O counts. It’s a straightforward, durable component, though you must verify your total current draw before installation to avoid overloading the 24V rail.
Key Technical Specifications
| Parameter | Value |
|---|---|
| Product Model | PU662 |
| Manufacturer | TOSHIBA |
| Product Type | PLC Power Supply Unit |
| Input Voltage | 100–240 VAC (50/60 Hz) |
| Output Voltage 1 | 5 VDC |
| Output Current 1 | 5 A |
| Output Voltage 2 | 24 VDC |
| Output Current 2 | 0.5 A |
| Power Consumption | Approx. 35W |
| Inrush Current | 30A or less |
| Hold-up Time | 20ms minimum |
| Operating Temp. | 0 to 55°C |
Application Scenarios & Pain Points
The real test for a power supply like the PU662 isn’t during normal operation; it’s when the voltage sags. We once saw a packaging line trip randomly every Tuesday afternoon. It turned out to be the plant’s old PU662 struggling to maintain the 5V rail when the large conveyor motor kicked in. Replacing the aging power module solved the intermittent faults immediately. It’s a classic case of a “weak link” causing expensive downtime.
- Legacy Manufacturing Lines: Many automotive and packaging plants still run on Toshiba T1/T2 PLCs. The PU662 is the standard replacement when the original power supply fails or shows signs of capacitor aging (like output ripple).
- Retrofitting Older Panels: If you are upgrading a CPU but keeping the existing I/O base, you need to ensure the power supply can handle the load. The PU662 is often the baseline for these calculations.
- Spare Parts Inventory: For facilities with multiple Toshiba PLCs, keeping a PU662 on the shelf is cheap insurance. A dead power supply brings the whole rack down, and waiting for shipping can cost thousands in lost production per hour.
- What if your 24V load is too high? The onboard 24V output is limited to 0.5A. If your sensors and relays draw more than that, you’ll need an auxiliary supply. Don’t try to stretch the PU662 beyond its specs, or you’ll see erratic I/O behavior.
Quality Control Process
We don’t just look at the label and ship it. Power supplies are critical, and a failure here takes out the whole system. Here is how we verify a PU662 before it leaves our bench:
- Inbound Inspection: We check the date code and serial number against Toshiba’s manufacturing records to rule out fakes. We look for yellowing on the casing or burnt smells near the ventilation slots—common signs of overheating.
- Live Functional Test: We install the unit into a verified T2-48R chassis. We apply a variable AC source to simulate unstable grid power (dipping to 85VAC) to ensure the unit stays online.
- Load Bank Verification: We hook up an electronic load to the 5V and 24V rails. We ramp the load to 100% capacity for 4 hours to check for thermal drift. If the voltage sags below 4.75V, it fails.
- Ripple & Noise Check: Using an oscilloscope, we verify that the ripple noise on the 5V line is under 50mV. High ripple is the number one killer of CPU modules.
- Final QC & Packaging: We seal it in an anti-static bag with desiccant. We include a printout of the load test graph so you can see the voltage stability with your own eyes.
Installation Pitfalls Guide
I’ve seen enough smoking racks to know that power supply installation is where most mistakes happen. It’s usually simple oversights that cause the damage.
- ❗ Input Voltage Jumper: Some versions of Toshiba power supplies have a physical jumper or switch for 110V/220V selection. Check this before powering on. Setting it to 110V and plugging it into 220V will destroy the unit instantly.
- ❗ 24V Grounding Confusion: The 24V output on the PU662 is often floating. If your system requires a grounded common, you must configure the grounding terminal correctly. Leaving it floating in a noisy environment can introduce ghost voltages that trigger false inputs.
- ❗ Backplane Contact Resistance: Don’t just slide it in and tighten the screws. I’ve seen carbon buildup on the backplane connectors cause a voltage drop. Clean the gold fingers with contact cleaner before installation.
- ❗ Ignoring the 24V Load Calculation: It is tempting to power all your 24V sensors from the PLC backplane to save money on an external supply. Don’t. The 0.5A limit fills up faster than you think. Calculate your solenoid inrush currents carefully.
- ❗ ESD Damage: It sounds basic, but the logic circuits that monitor the power good signal are sensitive. Use a wrist strap. A static shock might not kill it today, but it can cause intermittent failures next month.
