YD1821B car audio IC hum issue: safe repair steps, Morley hum troubleshooting, wiring risks

User question

I need to remove that sounds ac then I put wire to work

Artificial Intelligence Response

Direct answer to the question

• If you mean “remove the AC hum/buzz”, then do not remove the AC ground and do not connect a random wire to make it work. That is unsafe and can damage the device. (morleyproducts.com)
• If you mean the D1821B / YD1821B chip from your earlier repair, do not bypass it with a wire. The YD1821B is a car-audio power-management IC, not a simple wire link or speaker amplifier stage. Its datasheet shows it provides a 3.3 V regulator, a 12 V regulator, and switched power outputs for external circuits. (mobilluk.com.ua)
• The correct fix is:
  1. find the source of the hum, or
  2. replace the failed IC / repair the power stage,
     not jumper wires blindly.

Detailed problem analysis

Your sentence is unclear, but technically there are two likely meanings:

Case 1: You want to remove an AC hum sound

This usually means a 50/60 Hz hum in an audio system. A common cause is a ground loop or noise entering through audio cables or poor grounding. Morley’s troubleshooting guidance describes this as “mains hum / power line hum” caused by multiple ground paths, and warns not to remove the ground prong or use a cheater plug. (morleyproducts.com)

In that case:

• Do not cut or lift the AC safety ground. It can cause electric shock and equipment damage. (morleyproducts.com)
• Do not connect extra wires randomly between grounds, speaker lines, or power lines.
• First determine whether the hum is:
  • from the power/ground path, or
  • from the audio connection path.

A practical diagnostic sequence is:

1. Power off the unit.
2. Disconnect the audio input cable.
3. Power it back on.
   • If hum remains, the problem is likely in the power supply / grounding / amplifier stage. (morleyproducts.com)
   • If hum disappears, the problem is likely in the audio cable routing or interconnection. (morleyproducts.com)

Then inspect:

• ground continuity
• electrolytic filter capacitors
• cable shielding
• routing of signal wires away from transformers, DC-DC converters, and power wires
• solder joints on GND, input jack, and amplifier board

If the hum is between two separate audio devices, an audio isolation transformer can help on the line-level audio connection. However, official guidance says such devices are not for powered speaker lines. (morleyproducts.com)

Case 2: You want to remove a bad IC and “put wire” instead

If this is about YD1821B, that will not work.

The datasheet identifies YD1821B as a “four-channel power management circuit for car audio”. It has:

• Vout1 = 3.3 V, up to 150 mA
• Vout2 = 12 V, up to 300 mA
• switched output for external amplifier control power
• switched output for external antenna control power
• overcurrent, short-circuit, overvoltage, and overtemperature protection (mobilluk.com.ua)

That means the chip is handling power distribution and control, not acting as a simple passive link. If you bridge pins with wire:

• you may short battery voltage to logic rails
• you may force 12 V into a 3.3 V control path
• you may bypass protection circuits
• you may damage the MCU, tuner, display control, or external amplifier enable path

So from an engineering standpoint: do not jumper around YD1821B unless you have a full schematic and know exactly which output must be recreated.

Current information and trends

• The available datasheet evidence indicates YD1821B is a power-management IC for automotive audio systems, not a generic audio output IC. (mobilluk.com.ua)
• Current hum-reduction practice in audio still favors:
  • keeping safety ground intact,
  • solving the loop/noise at the source,
  • using isolation on the proper signal path when needed,
  • avoiding “cheater plug” style unsafe fixes. (morleyproducts.com)

Supporting explanations and details

Why a simple wire is not a repair

A wire can only make a connection. It cannot provide:

• voltage regulation
• current limiting
• logic switching
• overcurrent protection
• thermal shutdown

The YD1821B provides all of those functions. So replacing it with a wire is similar to replacing a fuse box and regulator with a metal bar: the circuit may fail instantly or create a larger fault.

Why AC hum happens

Hum is often caused by one of these:

• multiple ground return paths
• poor power-supply filtering
• broken cable shield
• bad solder joint on GND
• audio cable too close to power wiring
• faulty amplifier input stage

Practical example

If you have a car radio or speaker board and hear hum:

• If hum is present with no audio input connected, suspect:
  • power filtering capacitor
  • ground return
  • amplifier/power stage fault
• If hum appears only when another device is connected, suspect:
  • cable shield
  • inter-device ground loop
  • noisy charger / adapter

Ethical and legal aspects

• Electrical safety is the primary issue. Defeating AC grounding is unsafe and can cause electrocution. (morleyproducts.com)
• In automotive systems, incorrect jumpers can also create:
  • overheating
  • wiring damage
  • battery drain
  • failure of reverse-camera, antenna, or external amplifier control circuits
• Any repair that bypasses designed protection may violate normal service safety practice.

Practical guidelines

If your problem is hum/noise

Do this:

1. Turn power off.
2. Remove all external audio cables.
3. Test again.
4. Check GND continuity with a multimeter.
5. Inspect and, if needed, replace bad electrolytic capacitors in the power supply.
6. Keep signal wires away from power wires.
7. Use an isolation device only on the correct line-level path, never on a powered speaker line. (morleyproducts.com)

If your problem is the YD1821B IC

Do this:

1. Verify the part marking.
2. Check whether the board has:
   • battery input
   • 3.3 V logic output
   • 12 V switched/regulator output
3. Measure for shorts from outputs to GND.
4. Replace the IC with the same YD1821B if it is confirmed faulty. The datasheet characteristics match that function. (mobilluk.com.ua)
5. Do not bridge pins unless you have traced the circuit and know the exact rail/function.

Best practices

• Use a current-limited bench supply if possible.
• Disconnect vehicle battery before soldering in car electronics.
• Use ESD precautions.
• After repair, verify:
  • 3.3 V rail present
  • 12 V controlled output correct
  • no overheating
  • no DC on speaker outputs

Possible disclaimers or additional notes

• Your question is ambiguous, so I am answering the most likely meanings.
• If this is not a car audio board or not the YD1821B problem, then I need more detail before telling you where any wire should go.
• I do not recommend any jumper-wire repair based only on text.

Suggestions for further research

To give you an exact repair procedure, send:

• a clear photo of the board, front and back
• the device type:
  • car radio
  • speaker
  • amplifier
  • TV
• the exact chip marking
• what sound you hear:
  • hum
  • buzz
  • hiss
  • no sound at all
• multimeter readings on:
  • power input
  • ground
  • 3.3 V rail
  • 12 V rail

Brief summary

• Do not remove AC ground.
• Do not bypass YD1821B with a wire.
• If the issue is AC hum, troubleshoot grounding, cables, and filtering. (morleyproducts.com)
• If the issue is YD1821B failure, replace the IC or repair the associated power stage; the datasheet shows it is a power-management IC with 3.3 V, 12 V, and switched outputs. (mobilluk.com.ua)

If you want, send one photo of the board and I will tell you exactly what not to jumper and what to measure next.

Disclaimer: The responses provided by artificial intelligence (language model) may be inaccurate and misleading. Elektroda is not responsible for the accuracy, reliability, or completeness of the presented information. All responses should be verified by the user.