Hi all! Just got a cheap HRD MIM and it works fine, all tubes glow, no crazy noise problems, reverb and channels function fine but it was in storage a while and the bass tone knob isn’t working. So the amp sounds very thin. Any ideas of what the problem is? I own a guitar repair business and have some limited experience working on amps, so if there is a way I can save a trip to my amp tech, I’m all ears. Thanks!