Final answer.
For those ppl who own 622/722 and suffer from all issues relating to overheating HDD and components ( and not afraid do this mod ) I'm presenting perfectly working solution.
After months of thinking, 3D modeling of air-flow and temperature of main components [three main BCM chips, HDD, two demods BCM4500 and a couple of hi-pot regulators on power supply PCB ) and play with different fans, position and voltage I fixed the problem.
If Dish will follow my design, I prefer if I will be copyrighted it by publishing here.
What I did consider:
- cooling air must come into the box strictly from outside;
- three possible position for new fan:
-- a) 40-50mm on back side, right above two sat cans; best position but the small size of fan and noise/airflow ratio wasn't acceptable ;
-- b) on top, blowing down to BCM4500s ( right side if you have front panel looking at you ) and under HDD to main BCMs to power supply [PS] ; good position, you can use 80mm fan, but airflow will go out mostly to right side, not to the left - not effective;
-- c) use same 80mm 12 VDC fan in a middle of volume; slow down its rotation using internal 3.3V (RS232/UART) or 5V from USB connector.
So, I took last approach - you can see it on my pictures.
Passed months, a temperature showing by Diags Counters still at 111/84/95; whispering of the fan you can hear from 3 feet max midnight ( at 3.3V ); I did measure of warmest spot at left grill ( near PS) - during hottest days w/out AC it was 120F, regulary - less then 100F.
I see positive moments in the design:-
- 80mm fun is cheap
- powering it at 3.3V reduce noise and produce enough CFM to keep DVR cool
- intake air taking directly from your room
- delivering it to hi-pot components directly: HDD, BCMs and power supply
- space for the fan is available
- using those four plastic rivets is very convinient; no need any tool to remove them in case if a cover should be open
- quiet.
