Hopefully I can find some assistance here. I have two Denon AVP-A1HDCI preamplifiers, each with different issues. Both power on and work from one degree to another. The first, I paid $200 for. I believe it has a failed HDMI board. Optical inputs work fine. HDMI monitor out functions and I can view and use the menu through my TV. However, when I plug my Denon DVD-5910 in to it, the DVD player freezes and I can not use any functions on the DVD player until I unplug the HDMI cable and shut off and turn back on the DVD player. This occurs on any HDMI input port. (HDMI cable is fine. I can plug cable into my TV and it functions normally. I have been using it this way for the time being and using an optical cable from DVD player to preamp with nos issues). The second unit also powers on, the HDMI board seems to be functioning. I can use the same DVD player and HDMI cord plugged in to the preamplifier and plug the TV in to the monitor port and the DVD player functions normally, produces sound and picture; however, the sound is low and hollow (almost like a bad ground). In addition, the optical input produces the same weak sound, but has the additional issue of cutting in and out. I am thinking a failed digital audio board (rca inputs produce full sound). Some additional issues with the first unit. I have not been able to use the Denon link with the DVD player. Also, the Audyssey mic worked the first time I used it, but gave an error of not hearing it the next time. The second unit will run Audyssey set up with same mic, but sound is to low register (same weak sound). I paid $50 for the second unit and it is mint looking. As such I am hoping to make use of it. These units are packed full of components. How difficult are they to disassemble and swap boards around in? Any other suggestions as to where to start? Thanks for any advice.