Phono stage noise after some time

Hi, I've got two units, a used B&K Pro-10MC pre-amp that I bought used back in 2003, and a Grado PH-1 that I bought in Bangkok last year. I live in Thailand, and I have my music system set up in my office with my computers. I use my Thorens TT to convert old vinyl to 24-big AIFF and then to CD and FLAC via a USBPre.

I noticed a while back that my B&K phono stage, which seemed to be "silent" when I first got it, started to present audible "white" noise when I turned up the volume. I noticed with with headphones and also through my A/D converter.

Not knowing where to turn, and just assuming my used unit was getting old, I found a new Grado PH-1 in Bankgok. It sounded great at first, but after a period of time I noticed noise with it as well. My Thorens wiring was always a bit funky, so I had it repaired. I sent the Grado back to NY to have it checked out, and was told it was fine.

But when I plug it into my A/D converter I still hear very appreciable noise. Same in the B&K. This is without any turntable plugged in (so it is not a grounding issue or anything like that).

My question to this forum is this. Could the harsh, generally hot and humid environment I live in be causing corrosion or other deterioration to my B&K and Grado electronics? I use A/C when I'm in my office, but obviously not when I'm away for a length of time, over night, etc., so the temperature fluctuates.

If the heat/humidity/temp fluctuation is the cause of increased noise, can it be fixed by a professional (removing corrosion) or something like that?

My B&K does not create noise in the other inputs, just the phone-stage, which has me perplexed. I'm ready to give up and just record my 300+ records with the noise as if I was just recording to cassette and forget about getting the best archive quality possible. But I hate to settle for that.

If the environment is the cause, I'm not sure buying something new is going to help for long.

What can I do?

Your input is appreciated.