I recently acquired an older Hartke 3500 (one of the "mosfet" models, I'd guess late '80's) and replaced the power tube. However, it still crackles and pops. According to the guy I acquired it from, it needs to be "blown out", which he explained means cleaned thoroughly with compressed air, to get dust off of the EQ sliders, etc. Is there a way to do this myself, hopefully with less expense than taking it to an electronics shop and paying through the nose for labor? Anyone with any suggestions should email them to email@example.com. Thanks in advance for your advice.