Repairing Power Flicker on Denon AVR X5700H Receiver

Power flicker in a Denon AVR X5700H can feel like an annoying nuisance or a potential safety risk. The receiver may momentarily dim, produce a brief hiss, or even shut down as the voltage supply stutters. These symptoms not only interrupt your listening experience but can also signal underlying electrical problems that may damage the AVR or connected components. The following guide takes you through a comprehensive, step‑by‑step repair process that covers diagnostics, internal inspection, component replacement, and preventive measures.

Why Power Flicker Happens

The Denon AVR X5700H, like any high‑end home‑audio device, draws a steady DC supply from the AC mains. If the AC line is unstable, the internal power supply may not filter the waveform cleanly, causing voltage spikes or drops that appear as flicker. Common causes include:

• Loose or damaged mains cables that introduce resistance and voltage loss.
• Faulty internal power supply components such as electrolytic capacitors that have degraded over time.
• Electromagnetic interference (EMI) from nearby devices or an overloaded power circuit.
• Surge protection failures that allow high‑frequency spikes to reach the AVR.

Knowing these typical culprits helps you focus your troubleshooting and reduces unnecessary disassembly.

Preparation and Safety

Before touching any part of the AVR, safety must be your top priority.

1. Unplug the unit from the wall outlet.
2. Discharge static: Use a grounded wrist strap or touch a grounded metal object before opening the chassis.
3. Remove all accessories (cables, speakers, remote controls) so that you have a clear workspace.
4. Keep a small flashlight or lamp handy – the interior can be dark.

These steps protect both you and the delicate electronics inside the receiver.

Step 1: Verify the Symptom

The first thing you need to confirm is that the flicker is not an artifact of the display or a software glitch.

• Listen for a faint hissing or a sharp click that coincides with the flicker.
• Observe the screen: does it flash to black or display a “power low” warning?
• Check the speakers: do they emit a pulsing tone or a sudden drop in volume?

If you observe a consistent drop in the displayed voltage or a repeating audio glitch, you can proceed with confidence that the issue is electrical rather than cosmetic.

Step 2: Check the Power Source

External factors can mimic internal problems.

Test a Different Outlet

• Plug the AVR into a different, known‑good outlet.
• If the flicker disappears, the original outlet was the problem.

Inspect the Power Cable

• Look for kinks, frayed insulation, or a bent connector.
• Replace the cable with a known‑good one of the same length and rating.

Verify Mains Voltage

Using a household voltmeter or a multimeter set to AC, read the mains voltage:

• The standard US mains is 120 V ± 5 %.
• Europe uses 230 V ± 5 %.

If the mains voltage is outside these ranges, you may need a voltage regulator or to contact your utility provider.

Step 3: Measure the Receiver’s Input Voltage

A properly functioning power supply should deliver a stable DC output, but the AVR’s front panel can only display AC voltage. Use a multimeter to check the internal DC rail that powers the main board.

1. Open the chassis: locate the side panel screws and gently remove the back plate.
2. Locate the power supply board: it’s usually a rectangular PCB near the power jack.
3. Identify the 12 V DC output: it’s the main rail that feeds the receiver.
4. Measure the voltage with the multimeter in DC mode.

A reading that fluctuates by more than ±1 V or spikes above the expected 12 V can indicate a failing regulator or capacitor.

Step 4: Inspect Internal Power Supply Components

If the external checks are clean but flicker persists, the problem lies inside.

Visual Inspection

• Check for bulging electrolytic capacitors: these are the most common failure point.
• Look for scorch marks or a burnt smell—signs of overheating.
• Ensure all connectors are seated: a loose connection to the main board can cause intermittent voltage.

Clean the Board

Dust and debris can create static or poor contact.

• Use a can of compressed air to blow dust from the power board.
• For stubborn grime, a small brush can be employed, but avoid touching sensitive components.

Test Key Components

If you have a multimeter with an AC‑to‑DC conversion function, you can test the voltage regulator’s output after it passes through the onboard capacitors.

Step 5: Replace Faulty Capacitors

Electrolytic capacitors are notorious for failing after years of operation.

1. Identify the faulty capacitor: usually marked with a part number and value (e.g., 220 µF, 35 V).
2. Purchase a matching replacement: look for the same capacitance, voltage rating, and equivalent ESR (equivalent series resistance).
3. Desolder the old capacitor: use a soldering iron and a desoldering braid or vacuum pump.
4. Solder the new capacitor: make sure the polarity is correct—electrolytic capacitors are polarized.
5. Check solder joints: they should be smooth and free of cracks.

If you are uncomfortable desoldering, it may be safer to replace the entire power supply board.

Step 6: Verify Ripple and Noise

After replacing components, you need to confirm that the power supply is no longer generating noise.

• Use a low‑noise oscilloscope or a multimeter with ripple measurement capability.
• Observe the 12 V rail: ripple should be below 20 mV peak‑to‑peak for a high‑quality AVR.
• Check the 5 V and 3.3 V rails: they should also have minimal ripple.

If the ripple remains high, consider adding an additional filtering capacitor or replacing the voltage regulator.

Step 7: Reassemble and Test

1. Re‑attach the chassis panels and secure all screws.
2. Reconnect the power cable and all external connections.
3. Plug in and power up the receiver.
4. Listen for flicker: run through a few test programs to ensure the issue is resolved.

If flicker persists, the problem may be external or elsewhere in the power supply chain.

Step 8: Dealing with External Power Issues

Even after a perfect internal repair, external factors can still cause flicker.

Use a Dedicated Circuit

High‑power devices like AVR receivers should occupy a dedicated circuit with at least a 20 A breaker to avoid shared voltage drops.

Employ a Power Conditioner

A power conditioner can filter out noise, stabilize voltage, and provide surge protection.

Avoid Overloading

Do not plug the AVR or other high‑draw appliances (e.g., vacuum, heater) into the same outlet as the receiver.

Check for EMI Sources

• Move large motors (e.g., refrigerator, air conditioner) away from the receiver’s location.
• Keep the AVR’s power cable separate from cable bundles that carry high‑frequency signals (HDMI, USB).

Preventive Maintenance Tips

• Clean the interior annually with compressed air to remove dust.
• Inspect the power cable every 6 months for wear.
• Keep the AVR in a well‑ventilated area to prevent heat buildup.
• Use a surge protector rated for at least 1,500 J to guard against spikes.

By following these guidelines, you reduce the likelihood of future flicker and extend the lifespan of your Denon AVR X5700H.

When to Seek Professional Help

If after all the steps above the flicker remains unresolved, the issue may be deeper than the power supply—perhaps involving the main board or the firmware. In such cases, contacting Denon support or a certified audio technician is recommended. They can perform a full diagnostic with specialized equipment and determine whether a board replacement or a firmware update is needed.

Power flicker can be a simple fix or a sign of a larger problem. By methodically checking the power source, inspecting internal components, and replacing degraded capacitors, you can restore stable operation to your Denon AVR X5700H and enjoy uninterrupted audio bliss.