Smoke from my HR23-700 today. Opened the case to find a capacitor (or other small pill looking device) had shorted out, burning the power board plastic about 3 mm all around. Terrible smell. Airing out the house for hours. I'm hoping the fix is as easy as replacing the power board. However I cannot find a HR23 power board for sale. Are the power boards for the 21, 22, 23, ans 24s the same? Are they interchangible? Thank you!!