I'm about 12 years late to this thread, but I bought this amp for $150 from a good friend that can no longer play. The hssing/crackling was always ambiently there, but never bugged me until today, and I was dedicated to find and solve it if possible. I remember reading about something like this before I purchased the amp from him, so I took off the grill and found this thread, which guided me through the process. My amp just sounds so much better now (after a little bit of on-amp EQ-ing also) and the hissing/crackling is completely gone. Thank you.