IREM M92 (In The Hunt) - Distorted Audio, VR1 Volume Control Has Almost No Effect

[E DOOM]

大家好，

我想请教一下关于IREM M92 PCB音频问题的建议。

比赛：在《猎杀》中

PCB在其他方面工作正常：

• 画面完美无缺。
• 游戏运行正常。
• 没有崩溃或其他明显故障。

唯一的问题是音效。

症状​

• 音乐、音效和配音都严重失真/削减。
• 整体音量非常大。
• VR1（音量电位器）几乎没有影响。从最小到最大旋转，体积几乎没有明显变化。

我已经做过的事​

• 更换了PCB上的所有电解电容。
• 我仔细检查了所有电容的数值、极性和安装。
• VR1的问题在更换电容之前就已经存在了，所以我不认为是电容更换导致的。
• 用DeoxIT清洁了该区域。
• 有趣的是，有两次清理后音量控制恢复正常，但大约运行10分钟后又停止工作，失真音频又出现了。
• 视频部分完全正常，游戏其他方面完全可玩。

我的问题​

• 有人以前在M92上见过这种故障吗？
• 原版VR1电位器在这些电路板上故障常见吗？
• 除了VR1，我应该先检查哪些组件？
  • MB3730 功率放大器
  • MC3403 运算放大器
  • 音频前级部分
  • 断线、裂缝或VR1接地问题
  • 还有其他常见的M92音频故障吗？

任何建议或排查建议都非常感谢。

谢谢！

 

[Crunch]

I was playing on my Ninja Baseball Batman PCB the other day that had also been recapped and I heard scratching audio. I played with the pot and it dropped audio here and there. Cleaned the pot and it was back. If the audio came back after cleaning for you I would start with replacing that.

The JP version of M92 are also notorious for leaking caps, so if they already leaked, take an inspection in the area of any cleanup or eaten traces that need repair as a side check.

 

[ShootTheCore]

I’ve had the audio DACs go out on M92 boards as well and cause scratchy audio.

 

[E DOOM]

I’ve had the audio DACs go out on M92 boards as well and cause scratchy audio.

The audio issue on the Irem M92 board has been resolved. After replacing VR1 with a new component, sound returned to normal. The original VR1 was faulty; poor grounding prevented voltage division, resulting in permanently maximum volume and heavy distortion.

 

[ShootTheCore]

Great job!