May I sorry for digging up this old thread.
I just bought a JVC M70 in good cosmetics but have some problems that need your helps to deal with.
First, sound level is a little bit higher on left speaker than right, although it's hard to recognize at times. VU meter level also is a bit higher on left channel. However, I can hear good bass, treble, mids from both speakers.
Volume sliders are working ok I think. They are hard to slide but they just did their job, the sound increases normally as I slide up them.
And bigger problems are:
- when I turn up the box, it makes a short blast sound on left speakers (woofer and tweeter) but not quite loud, and occasionally from the right speaker too (in that case, the right speaker makes much more louder blast sound). And at the same time, the two VU needles move a lot, especially the RIGHT one - it move full to the end.
- when the box is powered up, on all functions, at all volume level, a hum/drone sound is heard from the LEFT speaker. It's quite loud, enough to heard from 4-5 meters if the music is off.
- when I turn off the box, the blast sound happens again on LEFT speaker, much louder than it's when turn on. I can see the left woofer jumping very hard, and a big noise also come from left tweeter. The sound is not very hard, I mean it's no hurt to the ears but is so annoying.
Also, the bass and treble control do nothing to sound quality. I have already opened the box and spray some contact cleaner to those sliders and function switch but nothing improved.
Edit: I do notice now that the Hum sound when box is turn on is actually come from both speakers. Much quieter on the Right side. And the sound is actually not retain the same level all the time, for each speaker, the noise varies if I slide the volume control, it's not necessary louder as volume is slided up, and become quite loud if volume is at top. I guest it's something more technically with the control board than just dirty.
Any help would be much appreciated.
Thank you very much!