Electronic design thoughts on newer model Onkyo Receivers

I recently took on a project that grew in scope and I learned some interesting things about newer Onkyo models that I thought I would share.

Background: I bought an Onkyo RZ820 off eBay (their high end model from this series) that was missing an HDMI board and a pre-amp board.  I had a dead RZ820 HDMI board lying around that I thought I could fix so I started to do some research to see if I could find the pre-amp board.  The unit arrived before I had ordered anything and I was very surprised and disappointed to find that the previous owner had removed the screws that held the heatsink in place.  Couple this with rough shipping from FedEx and as the attached picture shows, the main board was broken in half.

During my research I realized that the NR575/NR676/HT-R997/RZ620/NR777 and RZ720 all used many of the same Printed Circuit Board (PCB's) but each model was populated differently to provide features (like higher end power transistors, Pre-Out connectors, Zone3 etc).  Of course, the front panel was completely different and the RZ820 is a taller unit so Onkyo created a custom DAC filter board (the riser board at the rear of the unit) and they upgraded the transformer to match with the higher power transistors.  It soon became obvious that Onkyo was in a cost cutting mode and were trying to leverage (essentially) one design to create multiple different models.  Interestingly, all of these models use the same firmware package from Onkyo so the only logical difference between them is the "personality module" (small EEPROM) with unit specific configuration info.

With this in mind, I bought a dead NR676 off eBay but when it arrived, I found that I had an NR686 with a blown amplifier circuit so I ordered another NR676 so that I would have the parts I needed.  When I took the NR686 apart, I quickly realized that it had the same Main board, the same power supply, the same HDMI board and the same speaker-out PCB's as the RZ820 but it was too late for me to cancel the order for the NR676.  Again, they had populated the boards differently but all of the traces were laid out to accommodate multiple models.  Later, when the NR676 arrived (some child had inserted a screwdriver into each HDMI port and broke all of their contacts) I compared the 3 systems.  I quickly repaired the NR686, upgraded the firmware and since it was in pretty good shape, I decided against using it as my donor but I was surprised when I compared it to the NR676 and found that they were electrically identical.  Literally, the only physical difference in the NR676 and the NR686 was the printing of the model on the front/rear of the unit.  Upon further investigation, I realized that the only difference between the two was the firmware that was loaded onto the NR686 to provide some new features (Google support for example).

Deciding to use the NR676 as my "donor", I was able to repopulate the board into an RZ820 configuration by moving a ton of components from the broken board to the NR676 board.  I was then able to rebuild my RZ820 HDMI board (Main CPU blown, Video Processor blown, Network Processor blown and both HDMI controllers blown).  While doing this, I systematically disassembled a dead RZ810 HDMI board (bad HDMI chips) and used the good parts to rebuild the RZ820.  I did have to buy a couple of new HDMI parts out of China but after all this work I now have a fully functional RZ820 and a fully functional NR686.  Since the NR676 HDMI board seemed good (except for the broken HDMI ports) I replaced all of those ports with parts from the RZ810 and then moved the Zone 3/Fan/RS232 circuitry from the RZ810 over to the NR676 board.  I then copied the personality module from the RZ820 to the NR676 board and have a good working spare RZ820 HDMI board as well.

I wasn't sure this was possible but thought it might help others to know that parts from other Onkyo units may be able to be converted if necessary.

HTH

Todd