622 Temp. Measurements and Mitigation Trials
Hello, all! Well I finally got around to doing some 622 temperature testing and mitigation trials of my own, like Mark_AR has been doing. I wanted a better, "real-time" feedback so I did some temp. probing vs. waiting for the results in the HDD temp. readings counters. I won't comment again on my motivation for this effort - I think most of us agree on that!
DISCLAIMER: I took some personal and equipment risks doing this! Don't attempt doing anything inside a unit unless you have a good idea of what you're doing and the associated risks, and unless you are willing to accept the consequences of your actions. Opening a unit may void the warranty. (I did not break the internal warranty seal covering a fan bracket mounting screw nor do any disassembly other than removing the cover.)
This is my replacement "E" version unit. In a nonscientific assessment it does seem to run a bit cooler to the touch on the outside vs. my returned "D" version. Upon initial internal inspection there does not seem to be any visible difference between my unit and Mark's (not sure what version he has). There are no additional heatsinks, vents, or fans or such.
I used a Sears 34.82400 autoranging DMM with the K-type thermocouple that comes with it (see photos). The 622 was powered at all times - I was actually watching a program via HDMI throughout these trials (immediate feedback for any "whoops" events!) but not recording anything other than what the HDD is doing for normal viewing. My counters initially read 125 HI, 84 LO, 104 AVG. They were the same after these trials. The ambient was around 74F when I started. (It actually rose to over 80F, but the wall thermometer is close to the TV that had been off prior to the first reading.) At no time was the 622's internal fan seen to be running. I never saw any unusual changes in the HD PQ, SS audio, or performance that might be attributable to my "invasion".
I quickly realized that there are MANY heat generators in this unit, not just the HDD! There are 3 power semiconductors with heatsinks in the power supply that were all too hot to touch, and another on the main PCB that I didn't try. And ALL of the Broadcom chips were VERY hot, particularly the large one just below/behind the HDD. That one seemed the hottest so I focused on it for these initial trials.
I checked the temp. probe (poor-man's calibration!) by first inserting it into the ice on the freezer right next to the 622 (~30F) and then into my hot tub (~95F, matched the thermometer +1deg.) and those readings seemed in line.
I first measured the temp. on the upper rear case of the HDD - about 118F. I then measured the BC chip. The TC tip was just touching the top of the BC chip on its "silver" part in about the center (photo1). At that time (with the cover off about 15 minutes) the chip was about 130F, almost too hot to touch. After some lack of repeatability in my measurements I realized that where I measure on that chip made a difference, so I had to repeat my measurements. The results below were based on a relative "hot spot" on the chip and I did my best to make sure the contact point and "pressure" remained constant.
I wanted to test the unit with the cover on, off, and with some added cooling. The cooling was primarily accomplished with the cover off and a very cheap 3-fan laptop cooler blowing down into the unit (photo 2). This is a very mild airflow (I forget the volume, but I do have the spec. sheet), probably a good bit less than what the internal fan can provide. After several trials I obtained reasonably repeatable results (+/- 3-5F) as follows:
Cover on: ~160F
Cover off: 130-135F
Fans over open unit, off: ~150F
Fans over open unit, on: 100-105F
Cover on - one fan blowing in from right side vents: ~155F
This morning after 6+hrs standby, fans running (ambient 68F): 99F
Some reasonable observations/conclusions/commentary:
1) The BC chips are major contributors to the internal heat. (At one time the meter indicated 170F (!) on that chip, but I couldn't repeat that measurement.)
2) Removing the cover alone allows the tested chip to cool by about 25F.
3) Air moving over the chip(s) is indeed necessary (as Mark_AR reported) to obtain significant cooling. In my experiment that amounted to almost 60F !! (Part of that may be due to the fact that the top was still partially open.) I also believe that flow needs to be ambient air from outside the case, not just internal air moved around, altho' that alone probably helps somewhat.
4) The internal fan is doing essentially NOTHING to help the situation. I believe it may operate only during extreme situations, but how hot does it need to be? Close to spontaneous combustion, as one poster feared ?? (There seems to be considerable variabillity here as ralfyguy reported that his fan is always running. How can we manage that in all these units? No apparent adjustment.)
5) Apparently modest swings downward in ambient temp. / standby time don't make much difference in the low temp. readings.
Some additional questions / ideas for further investigation:
1) How much heat does the HDD contribute? Does its temp. vary measurably with additional activity, i.e., if it's "very busy" with multiple R/Ws due to recording multiple programs, etc. will its temp. increase considerably?
2) What would heatsinking the BC chips do to lower their temps.? (I don't think that alone will help much - there also needs to be moving air.)
3) How much will the large BC chip's temp. change if it is "busy" with MPEG-4 decoding or such. (I'm assuming that's where the decoding activity is.)
Where I will go from here:
I plan to make an out-board fan system using 3 or 4 of those fans shown mounted into a block of styrofoam or such and held in place to cover the vents on the left (power supply) side. I can then vary the direction of flow and the number of fans running to see what makes the most difference in the internal readings. I might also place a single fan over the right side vents to work in conjunction with or opposing the left-side fans. I'm also considering another internal fan similar to what Mark did, but perhaps focused to the hottest chip.
I'll leave the TC inside the unit for now (place and mounting method TBD, but probably held more firmly on the top of that same BC chip) so I can take frequent readings. I am concerned about providing adequate filtering for the outside air, which then also leads to a question about what happens if the filters get clogged-up? Probably worse than no fans!
I hope this provides some additional insight and motivation for further experimentation to find the most viable mitigation techniques to solve our universal "problem". At least it's a great discussion/debate!
More to follow. Thanks for reading and BRgds...