I broke the variable resistance knob on my AP74. I called DYNON to discuss repairs. His response was that that their repair charges start at $450 (I could be wrong but the number was definitely north of $400). I told him that if it was that expensive I’ll just buy a née unit. His response was let’s take a look. We should be able to replace the knob. Bottom line; I got it repaired for about $150. I’m a big fan of DYNON Support!!!