which way should cooling fan blow?

[Peter Howard]

In the last half of 2003 I bought a Digitrex GKX9000 DVD recorder from Big
W. Big mistake, as I found out when I started frequenting an Australian
website and forum devoted entirely to the GKX9000 (The site seems to be no
longer in existence). It was full of reports of the failings of this unit
and the non-responsiveness of the local distributors and warranty service
people. By the time I decided it was a dead loss I'd mislaid the receipt and
packaging and so could not return it to Big W.
I've just bought a decent standalone DVDR, but in a spirit of general
cussedness or masochism I'm taking another look at the Digitrex. One of the
many failings of this model was frequent lockups when it would not respond
to any button pushes or remote control commands. Others besides me observed
that it would often lock up part way through a recording, or fail to start
recording at a preset time. Only way to reawaken it was to unplug it from
the mains and power up again.

I know next to nothing about DVDR's but on opening the Digitrex up I see a
disk drive, an SMPS board, an I/O board and what seems to be a processor
board sporting a many-pinned SM chip with an aluminium heatsink stuck to it.
There is no cooling fan on heatsink and the only existing fan is a 40 mm
exhaust job at the other end of the case. As I know from experience, a PC
with a failed CPU fan goes into thermal shutdown. Could it be that this CPU
(if that's what it is) in the Digitrex needs more cooling than it gets?
The top cover of the unit is 38mm above the top of the heatsink, ample room
to carve a round hole in the top cover and fit an 80 mm 12v fan I happen to
have. I'm game to experiment along these lines because I'd hesitate to even
give this POS away let alone Ebay it to another unsuspecting boob.

The question is, should I arrange this fan to blow room temperature air onto
the CPU heatsink or suck warm air out of the case?
And should I incorporate a spacer to get the fan which is 20mm thick as
close as possible to the heatsink?
The 40 mm fan at the far end of the case sucks air and there's room to fit
one or more extras beside it if I wanted to be sure of creating a little
more negative pressure inside the case.

PH

 

[Lord Garth]

"Peter Howard" <bbrover109@bbbigpond.net.au> wrote in message
news:Cyaxd.78727$K7.60845@news-server.bigpond.net.au...



When my Oritron DVD player quit responding to remote or front panel
commands, I opened
it and discovered two blown electrolytic capacitors on the SMPS board.
Replacing these
cured the machine. The front panel indicated power at all times during the
problem.

 

[KLR]

On Sun, 19 Dec 2004 08:00:34 GMT, "Peter Howard"
<bbrover109@bbbigpond.net.au> wrote:

In the last half of 2003 I bought a Digitrex GKX9000 DVD recorder from Big
W. Big mistake, as I found out when I started frequenting an Australian
website and forum devoted entirely to the GKX9000 (The site seems to be no
longer in existence). It was full of reports of the failings of this unit
and the non-responsiveness of the local distributors and warranty service
people. By the time I decided it was a dead loss I'd mislaid the receipt and
packaging and so could not return it to Big W.
I've just bought a decent standalone DVDR, but in a spirit of general
cussedness or masochism I'm taking another look at the Digitrex. One of the
many failings of this model was frequent lockups when it would not respond
to any button pushes or remote control commands. Others besides me observed
that it would often lock up part way through a recording, or fail to start
recording at a preset time. Only way to reawaken it was to unplug it from
the mains and power up again.

I know next to nothing about DVDR's but on opening the Digitrex up I see a
disk drive, an SMPS board, an I/O board and what seems to be a processor
board sporting a many-pinned SM chip with an aluminium heatsink stuck to it.
There is no cooling fan on heatsink and the only existing fan is a 40 mm
exhaust job at the other end of the case. As I know from experience, a PC
with a failed CPU fan goes into thermal shutdown. Could it be that this CPU
(if that's what it is) in the Digitrex needs more cooling than it gets?
The top cover of the unit is 38mm above the top of the heatsink, ample room
to carve a round hole in the top cover and fit an 80 mm 12v fan I happen to
have. I'm game to experiment along these lines because I'd hesitate to even
give this POS away let alone Ebay it to another unsuspecting boob.

The question is, should I arrange this fan to blow room temperature air onto
the CPU heatsink or suck warm air out of the case?
And should I incorporate a spacer to get the fan which is 20mm thick as
close as possible to the heatsink?
The 40 mm fan at the far end of the case sucks air and there's room to fit
one or more extras beside it if I wanted to be sure of creating a little
more negative pressure inside the case.

PH

If you are putting the fan in the top of the case - then have it

blowing UP. Since hot air rises naturally - this natural action will
work with the fan helping blow in same direction instead of against
it.

Spacing it so it gets to the heatsink will certainly help - if the
heatsink is getting very hot in normal use.

If the thing gets really hot - and the IC underneath is similar shape
to a computer processor - it might be worthwhile actually installing a
CPU heatsink and inbuilt fan assembly

if its been running hot or overheated in the past, then you could
check for dry or bad solder joints under heatsinked devices, and also
check for eletrolytics too as they tend to have a reduced life when
hot.



Don't go overboard with fans though, in my experience they should only
be used as a last resort as they tend to suck heaps of dirt and dust
and crap into the unit, which in extreme cases:

1>blankets components, helping keep them hot,
2>gets into mechanical parts causing failures
3>clogs fins of heatsinks. vents and so on

if they fail, (and they do often) damage can occur to heat sensitive
parts.


in my opinion, good natural ventilaion, generous heatsinking areas and
should be a priority where it is practical or possible to do so.
Unfortunately with modern high performance processors and other chips,
short of slowing them down and bigger heatsinks (which defeats the
purpose of having them) - there isn't a lot you can do to avoid fans
in the real world.

 

[budgie]

On Sun, 19 Dec 2004 08:30:28 GMT, "Lord Garth" <LGarth@Tantalus.net> wrote:

"Peter Howard" <bbrover109@bbbigpond.net.au> wrote in message
news:Cyaxd.78727$K7.60845@news-server.bigpond.net.au...



When my Oritron DVD player quit responding to remote or front panel
commands, I opened
it and discovered two blown electrolytic capacitors on the SMPS board.
Replacing these
cured the machine. The front panel indicated power at all times during the
problem.

But if the O/P's machine responded after power cycling, it's a fair bet his
problem is different.

 

[Lord Garth]

"budgie" <me@privacy.net> wrote in message
news:4mnas0hesc6ngtqks8qf58dmhqjgrpoa5h@4ax.com...

On Sun, 19 Dec 2004 08:30:28 GMT, "Lord Garth" <LGarth@Tantalus.net
wrote:


"Peter Howard" <bbrover109@bbbigpond.net.au> wrote in message
news:Cyaxd.78727$K7.60845@news-server.bigpond.net.au...



When my Oritron DVD player quit responding to remote or front panel
commands, I opened
it and discovered two blown electrolytic capacitors on the SMPS board.
Replacing these
cured the machine. The front panel indicated power at all times during
the
problem.

But if the O/P's machine responded after power cycling, it's a fair bet
his
problem is different.

The Oriton did this as well...it worked intermittently, occasionally

requiring
a power cycle, until the components failed totally. The fix took 78 cents
and 15 minutes. Locating the probable failure was easy as the caps were
of the same brand often used on motherboards and were obviously swollen.
After removal, the leak was visible.

 

[WDino]

Many of the cheaper DVD recorders had two main problems, cooling and power
supplies, but even Panasonics and Pioneers also come in with similar faults
..
Both the CPU and the actual DVD writer tended to get too hot. The better
machines and later cheaper ones have CPUs with larger heatsinks. The DVD writer
is just a standard PC unit and can be replaced with a better one if desired.
Small fans blowing onto each have been known to help but I prefer to put a
larger fan inside the case blowing OUT.

As for the power supplies, the final filter capacitors tend to fail, usually
because they were mounted too close to the heat producing parts of the power
supply. Another fault was that the 5v supply drifted too LOW in voltage. In many
cases, DVD recorders came to me for repair that worked perfectly on my bench.
But when the 5v supply was checked it was less than 4.6V. Tweaking it up to 5.0V
usually fixed the machine for the customer.
The Digitrex GKX9000 DVD recorder is one that can need adjusting.

Peter Howard wrote:

In the last half of 2003 I bought a Digitrex GKX9000 DVD recorder from Big
W. Big mistake, as I found out when I started frequenting an Australian
website and forum devoted entirely to the GKX9000 (The site seems to be no
longer in existence). It was full of reports of the failings of this unit
and the non-responsiveness of the local distributors and warranty service
people. By the time I decided it was a dead loss I'd mislaid the receipt and
packaging and so could not return it to Big W.
I've just bought a decent standalone DVDR, but in a spirit of general
cussedness or masochism I'm taking another look at the Digitrex. One of the
many failings of this model was frequent lockups when it would not respond
to any button pushes or remote control commands. Others besides me observed
that it would often lock up part way through a recording, or fail to start
recording at a preset time. Only way to reawaken it was to unplug it from
the mains and power up again.

I know next to nothing about DVDR's but on opening the Digitrex up I see a
disk drive, an SMPS board, an I/O board and what seems to be a processor
board sporting a many-pinned SM chip with an aluminium heatsink stuck to it.
There is no cooling fan on heatsink and the only existing fan is a 40 mm
exhaust job at the other end of the case. As I know from experience, a PC
with a failed CPU fan goes into thermal shutdown. Could it be that this CPU
(if that's what it is) in the Digitrex needs more cooling than it gets?
The top cover of the unit is 38mm above the top of the heatsink, ample room
to carve a round hole in the top cover and fit an 80 mm 12v fan I happen to
have. I'm game to experiment along these lines because I'd hesitate to even
give this POS away let alone Ebay it to another unsuspecting boob.

The question is, should I arrange this fan to blow room temperature air onto
the CPU heatsink or suck warm air out of the case?
And should I incorporate a spacer to get the fan which is 20mm thick as
close as possible to the heatsink?
The 40 mm fan at the far end of the case sucks air and there's room to fit
one or more extras beside it if I wanted to be sure of creating a little
more negative pressure inside the case.

PH