@alightronics
When you say... "This issue might be caused by internal component loosening during long-distance shipping and multiple handlings."
I find that to be a very plausible explanation of what may have happened to the tube in question.
I went onto the AliExpress website and was looking all over the site for how I could initiate contact with them to discuss the noise issue that I'm having - with one tube of the matched pair of 845 Acme tubes that I had ordered. I couldn't for the life of me find how I can contact them.
Then a pop-up appeared asking to do a live chat and that they are there to help me. I clicked on it and had a long back and forth discussion with them where I explained the noise issue that happens upon start up, etc. They arranged for a return shipping label and said that I could return the tubes and that after their inspection my money would be refunded. I explained to the "chat person" that I simply wanted a replacement matched pair that actually works without defect, to be sent to me and that I did not want a refund. They then responded that I needed to contact the seller! I said that I thought this whole time I was communicating with the seller (AliExpress). They said no, we are just a "chat service" assisting the merchant!
I still do not know how to contact AliExpress! I guess I will have to just return the tubes via the return label provided; hope and pray I actually get my money refunded. I only say this because the return label receiving address is in Beverly, New Jersey USA. I thought AliExpress was in China? Along with the simple fact that I was not able to actually talk with anyone from AliExpress.
I will have to think long and hard to decide if I want to take another chance on ordering these again.
Although, I will say that these tubes sounded amazing in my amplifier and I was thrilled by that! So much so, that I was actually contemplating ordering a second matched pair for back up. However, the stress and anxiety of trying to return them and not being able to communicate with the seller is very frustrating to me and I'm not sure if it is worth it to me at the moment.
I guess I will wait and see if I actually receive my refund and then make my decision at that point.
Best wishes,
Don aka No_regrets