Does anyone have a schematic for a Laney HCM15 (or 30)?  How about a link to a site that has it available to download?
Thanks in advance.

Hi Luddite,
I just spent a bunch of time writing you a "proper" reply in an effort to help you figure this out, and the forum timed out on me and the whole thing was lost!
Hopefully, I don't sound snotty, but I am going to be brief with this.
Try replacing the tube in your pre-amp.  Even better if you use Caig Labs DeoxIT Gold Pen to clean your tube socket and treat the new tube before replacing.  Also, let your amp warm up for a few minutes after you turn it on before you play through the amp (ALWAYS).  Not warming the tube up will put you right back where you started in short order.
OK, hope this helps.
Quest Forth.
Sean
 
PS  As a side note, the DeoxIT Gold can be used for your preventive maintenance on all of your gear and is one of the best investments you can make in your gear and sound.