Thank you for the advice, but the headphone jack seems dead. I will ship this to family in California via express mail and have them return it to Amazon so I can get a refund. Amazon gives me a month to do this, and there's still time left.
The only reason I even knew about Amazon Warehouse Deals is because a kind person in this thread suggested it. But what I discovered is that Amazon is utterly incompetent when it comes to items sold there. I've used Amazon USA and Amazon Japan for YEARS without a single problem. Amazon Warehouse Deals comes with a very big caveat. First of all, I should say that I am a very meticulous person. I started 3 different Chats with an Amazon rep to confirm the condition and items included before I purchased. They answered most all my questions. When the unit arrived, it even had an "Inspected" sticker affixed to the box. But after finding out the headphone jack was dead (at which time I began posting here again), I also discovered that the wireless receiver unit for the remote control was not inside the box! The remote is there but not the companion IR receiver module. Then I discovered that the unit should have also come with a protective case for the D100, but that was no where to be found. Utter incompetence. There's no excuse for this, especially when I invoked 3 different chat sessions with them to confirm all would be well prior to purchase.
You folks in the US probably couldn't care less, and for good reason. When there's a problem, you just return it to Amazon for free. But for me, living in Japan, I must pay to get it transshipped to me, and then if there's a problem, I need to ship it to either family or a cooperative freight-forwarded who will print the required labels and then ship it back to Amazon, all within their designated time frame.
I've ordered a new unit, this time from B&H (since the sale price is cheaper than Amazon, and there is no tax, and the shipping is free too -- within the USA). I will then get it forwarded to me by family. Hopefully that will solve these messy problems.
Amazon Warehouse Deals... NEVER AGAIN!