Sony freeview box - is your pic breaking up?

valmiki

Standard Member
I just wanted to share something which has been bugging me for months now.

I have one of those sony freeview boxes that is white, and can be laid on it's sise, or standing up. dtx800 or something?

Every now and then, we noticed that the picture would start breaking up, especially on Channel 5, and some of the others ie ITV etc.

When it started to happen, I would sigh, and head to the back of the box among all the different leads and wires and start 'fiddling' in the hope of making some difference to the picture. Sometimes it would work, most of the time it would not. I could never figure out why it was happening, or how to sort it out!

People would suggest may be 'interference' or 'not a strong enough signal', all sorts.

So, finally, my powers of observation, finally cracked it.

The freeview box (with all the other av equipment) is in a stand that has about 6 shelves, glass doors on the front, and wheels on the bottom. The box occupies the very topmost shelf in the cabinet.

The picture on the sony box would only ever start to break up when the glass doors were shut! Open the doors, the interference disappears! Close the doors, the picture breaks up again! I can only explain it by something to do with the field generated by the magnetic door closers on the glass doors and the cabinet. As soon as they swing close together, the picture would start breaking up, not even necessarily that the doors were closed, just close enough for there to be an attraction.

Well, that sorted my life out no end! leave the glass doors open, SWMBO can now watch Charmed in peace and all is well in the world. Amazing that something so simple could hav been causing the problem all this time.

Hope this helps someone out there
 

ROYOLD

Well-known Member
The problem would appear to be heat buildup.
Leaving AV equipment which generates heat inside an enclosed cabinet is sheer madness. As you have found the heat buildup causes problems and it also leads to premature failure of electronic equipment. It may be too late in your case.
 

JayCee

Distinguished Member
pinipatel said:
I can only explain it by something to do with the field generated by the magnetic door closers on the glass doors
Rubbish, magnetic fields don't cause your symptoms...as Royold suggests it's probably heat build-up.
 

SamRadford

Well-known Member
Yes, once it's pizzafied you are too late. You can't uncook a pizza. It probably won't last long.
 

valmiki

Standard Member
I hear you all!

the cabinet isn't completely enclosed, there are numerous air passages in the back, and it is on quite a spacious shelf. ie. it's not rammed into a tiny enclosed space.

the breakup happens instantly, and even if one of the doors swings closed, ie. not closed properly but ajar.

you can't tell me that it's getting hot that quickly, just from swinging the door shut!

and, btw, it's been like this for the last few weeks and no change in any other behaviour. having said that, it is the first freeview box i ever bought, probably about 2-3 years old, so it's probably dying a slow death anyway.

i have a dvd in there, a dvd recorder, an av receiver, and a vhs recorder in there as well. none of them have been affected by any 'heat'.

you may discount my theory as due to 'heat' and not a magnetic field, but it works for me, so there :p~~ :)
 

mjbtin

Well-known Member
Had a problem last week with my Sony freeviews picture breaking up where it had previously been very good .My son installed a wireless router and placed it next to the Sony this caused the picture to break up very badly ,moving the router further away cured this problem .

Regards Martin:)
 

SamRadford

Well-known Member
Well, easy to test. Grab a magnet and move it close!
 

ianh64

Active Member
ROYOLD said:
The problem would appear to be heat buildup.
Leaving AV equipment which generates heat inside an enclosed cabinet is sheer madness. As you have found the heat buildup causes problems and it also leads to premature failure of electronic equipment. It may be too late in your case.
Within reason, I disagree with this. The ability of electronic and electro-mechanical components is quite high, especially since it is themselves that are generating the heat.

For the last 2+ years, I have used a glass fronted enclosed TV cabinet and before I put ventilation in it, internal temperature reached about 40 degrees on a reasonably hot day (mid 20's) after a good 10 hours of being continuously on. At 40 degrees ambient the media controller for the TV shuts itself down as a precautionary measure. So I think that it would be reasonably safe to expect a consumer box to work at 40 degrees ambient, which is pretty hot ambient temperature. My new Humax 9200 Freeview box for instance quotes a max working temperature as +45C which the cabinet has never reached in its past even when unventilated.

After putting ventilltion holes in the cabinet, ambient temperature dropped by a good 5+ degrees. In the heat we have had recently (34 degrees), the TV has shut itself down once.

So from my experience, temperature in a totally enclosed unventillated TV cabinet can be 15 degrees above ambient and with ventialltion about 5-10 degrees above ambient. For any reasonably designed piece of equipment with decent internal ventillation (ie not an overly compact design such as a Digifusion FVRT200) and using the case for heat disipation then 40 degrees is probably a safe maximum temperature for continued 100% reliability with spare tolerance. NB I was once paranoid about this and used a digital Max/Min thermometer on the shelves to monitor temperature over a a few hot weeks before and after ventillating the cabinet.

In normal use, the physical TV's media box is about 45 degrees (ie 5 degrees above max ambient cutoff) with an ambient temperature of 25 degrees in clear air. So even in clear air, the physical components and box themselves are working far in excess of the safe ambient cutoff limit.

So I think it would be reasonable to say that a box should safely and 100% reliably work in a clear air ambient temperature of 40 degrees or less when the units are not stacked - ie not physically touching with at least 10-20mm air gap between units - raised feet help significantly. This would be less than the non air conditioned ambient room temperature of a hot country. A fairly tightly packed enclosed cabinet with a fair number of components (ie media box, AV Amp, DVD, PVR, HD-STB, DVD-RW) with no ventilation could reach 40 degrees on a 25 degrees day after about 6 hours. With a reasonable amount of ventialltion and free air movement, 40 degrees would only be reached at the most extreme of room temperatures ie 34+ degrees. My ventialltion consists of 6 x 16mm holes drilled in base of cabinet and a 4cm2 chimney at the rear to extract the warm air. Currently, ambient room temperature of 20C, ambient cabinet temperature of 27C (+7C), chimney exit at 25 degrees (-2 from cabinet). Putting this in perspective, the LCD panel itself is 33C, TV media box 40C and Humax PVR 33C - the latter being on 24/7 and TV media box containing a HDD that is always on when TV is on - ie for last 2 1/2 hours.

My Pace PVR worked reliably for the last 2 years in this environment. It did have an electrical failure - a pair of capacitors costing £2 to replace that had a working temperature of 400 degrees of the same type and manufacturer who was involved in a scandle supplying duff components - so I dont think this failure was heat related. The unit was on pretty much 24/7 for 3+ years and was still working strong when it recently got replaced.

However a caviat is that manufacturers often quote 100mm clear air around units but this is often for electro magnetic interference. So always read your manufacturers instructions on placement before siting and use a bit of common sense if you feel that the distances specified are 'overly cautious'.
 

ianh64

Active Member
ROYOLD said:
Where?

It doesn't actually mention anything about temperatures anywhere. It makes the assumption that all heat is bad unless there is some way of actively moving it. It makes no consideration of passivly vented cabinets where inside temperatures, even after manu hours of continuous use, do not exceed the manufacturers recommended temperature specifications.

Basically, my own personal experience with an identical enclosure in both unvented and moteratly vented state indicates that, except under the most extreme of conditions, ambient temperature within the cabinet does not exceed the temperature that one could expect in a non airconditioned room of a hot country, let alone exceed the manufacturers specifications.

I would certainly recommend that a cabinet is moderatly vented (open back or holes in base and rear), but if a user is sensible to adhere to the maximum temperature specifications and not stack equipment in a poor manner (from both convected and direct heat transfer), IMHO enclosed cabinets do not pose a threat to the long term reliability of well designed equipment.
 

ROYOLD

Well-known Member
I wonder why manufacturers install extraction fans in pc's, dvd recorders, pvr's and the like. Seems to me they could save themselves some cash if they weren't at all bothered about heat buildup in the machine.

Then again, they may consider installing fans to be a good idea.
Saves all the hassle of returned U/S equipment.
 

ianh64

Active Member
Roy

It sounds like you are confusing the buildup of heat within the case of the STB etc with the ambient temperature inside the TV cabinet. Fans etc keep individual components within a STB within working specifications not keep the STB itself within manufacturs specified tolerances.

If a manufacturer states that a STB etc can work at 40C or 45C ambient, then if the ambient temperature within the TV cabinet is less than that then I can't see why you find "Leaving AV equipment which generates heat inside an enclosed cabinet is sheer madness. As you have found the heat buildup causes problems and it also leads to premature failure of electronic equipment."

In my own experience, measuring ambient cabinet temperatures over an extended period of time, I have never found that the ambient temperature is excessive when using moderate amounts of passive ventillation (ie holes in the cabinet) or, rarely exceeds 40C unless a unvented cabinet is used in the most extreme of room temperatures. What you are saying is that using a STB in a hot country is sheer madness and will fail prematurely.
 

LV426

Administrator
Staff member
As I see it, the issue is one of movement of air and not exclusively the local air temperature.

Moving air (and, even without a fan, in an open environment this will happen due to convection) of any temperature* will help dissipate heat from components whereas static air will not. Static air will therefore allow individual components' temperature to increase to a greater degree than moving air.

This is the primary reason why open cabinets, space between items of hardware and, of course, fans, all help preserve equipment.


_ _ _ _ _ _

* so long as its temperature is below that of the equipment
 

SamRadford

Well-known Member
If you are considering electronic components you should concentrate on the weakest link - the electrolytic capacitor. These are used extensively in most equipment and have a specific lifetime which is linked directly to their temperature. Typically the life expectancy will be something like 1000 hours at 105'C, doubling for every 10 degree decrease in temperature. So a 1000h/105 capacitor subjected to only 35'C can be expected to last 128,000 hours (15 years) at 35'C or 7.5 years at 45'C.

Where "end of life" generally refers to a 25% reduction in capacitance value - acceptable in most circuits.

However, this belies the fact that it's common practice for designers to ignore the effect of high-frequency pulses, which occur in most switch-mode power supplies. These can degrade electrolytics very quickly and in many cases (Grundig Digibox power supply units are a good example) the electrolytics will typically last only three years at 35'C or 6 years at 25'C.

Now you can see that temperature can play a major role in determining whether your Digibox lasts 3 years or 6 years, for example, dependent on other factors.

An additional problem is that a certain Taiwanese factory flooded the market with incorrectly manufactured capacitors a few years ago and the effect of this is still being felt, especially in the computer industry where many of the defective parts ended up.

References
http://www.niccomp.com/Products/General/Alumlyticlifeexpect.pdf (PDF)
http://www.niccomp.com/taiwanlowesr.htm
http://www.motherboardrepair.com

Anyway, to get back to the original problem, test it with a magnet in your hand.
 

valmiki

Standard Member
SamRadford said:
Anyway, to get back to the original problem, test it with a magnet in your hand.

armed with magnet, I moved it toward the freeview box in an arc-ing motion....


....and nothing.

scratched head for a while, and repeated procedure whilst also holding a piece of metal that would attract the magnet, and bingo! as the two were brought together (so that you could feel the attraction 'pull') close to the freeview box, the picture started blocking and breaking up.

I really don't know why it happens, just that it does, in my particular case.

[edit] I've added a pic of my cabinet, just to show what the situation is with the sony box in it
 

Attachments

ianh64

Active Member
SamRadford said:
...Typically the life expectancy will be something like 1000 hours at 105'C, doubling for every 10 degree decrease in temperature. So a 1000h/105 capacitor subjected to only 35'C can be expected to last 128,000 hours (15 years) at 35'C or 7.5 years at 45'C.
...
Now you can see that temperature can play a major role in determining whether your Digibox lasts 3 years or 6 years, for example, dependent on other factors.

An additional problem is that a certain Taiwanese factory flooded the market with incorrectly manufactured capacitors a few years ago and the effect of this is still being felt, especially in the computer industry where many of the defective parts ended up.
I agree with the above if the temperature on the component was as you state and 24/7/365, but we are talking about TV cabinet temperatures where only under the most extreme conditions are they reaching 40C. In some STB (which I include DVD-R/PVR etc) designs there is active cooling to further aid cooling within the STB box itself.

Normally my cabinet is between +5C and +10C above room ambient, depending on what components and how long they have been on for. Assuming that room ambient is normally 18C-21C, then we have an cabinet range of 23C-31C only reaching the upper limits of that after extended periods of al units being on (out of standby). Which is well within manufacturers specifications and, based upon the fugures you have used above, 30-15 years of continuous service.

Yes. My Pace box suffered with these duff capacitors. Cost £2 to fix. More of an inherrent manufacturing defect than a temperature related fault.

I still standby my comment that a TV cabinet with a modest amount of ventilation (such as to allow convection rather than air buildup) and a bit of common sense such as reasonable spacing between components and adhering to manufacturers specifications will not impact the reasonable (added reasonable to clarify) life expectancy of a product.
 

ROYOLD

Well-known Member
Aha Ian - so you have already had a digibox failure. My case rests.

As for pinipatel's cabinet picture. I don't think that the insurance company will pay out if it goes on fire. Heat rises - better to leave the doors open.

In my days at sea with the early marine radars
the magnetron failure was usually a result of inadequate cooling. We soon found that out.
As Sam Radford states heat is the cause of many electrical failures. Despite cabinet temps only being a max of 31 degs C the actual temperature inside the machine will be several degrees higher.

This PC has two hard drives mounted one above the other with approx 1 cm gap between the two. I have extra fans fitted to give extra cooling in the HDD area and yet, despite this, my HDD warning utility will advise that the temp is above critical - that's
46 degs C.

So definitely no cabinets for me I know the
effects of excess heat.
 

valmiki

Standard Member
ROYOLD said:
As for pinipatel's cabinet picture. I don't think that the insurance company will pay out if it goes on fire. Heat rises - better to leave the doors open.

apologies for sounding a little sceptical, but insurance companies not paying out if it goes on fire?! any more space in that cabinet and it wouldn't be one.

I forsee shares in IKEA dropping like a lead balloon if this gets out!
 

kevmarshall

Active Member
If I were you pinipatel, I would remove the magnets and replace them with some sticky backed velcro pads (B&Q)...............sorted!:smashin:
 

ianh64

Active Member
ROYOLD said:
Aha Ian - so you have already had a digibox failure. My case rests.
Ah, but the failed capacitors were identified as being from the type and manufacturer of faulty components which would have failed well before 3 1/2 years irrespective of whether the Pace box was inside a cabinet or not.
http://www.niccomp.com/taiwanlowesr.htm said:
Subsequent lifetime tests on low-ESR aluminum electrolytic capacitors produced in Taiwan by Japanese aluminum capacitor hours revealed the occurrence of catastrophic failure of the Taiwanese aluminum electrolytic capacitors after 2000 hours of operation on parts rated for 4000 hours of operation. Intel has stated that the aluminum capacitors with the poor electrolyte may fail after only 250 hours of operation.
I am happy to run my units inside an enclosed vented cabinet. And the manufacturers of my amp and DVD player were happy to soak test them under a blanket for 1 week to check for heat buildup - internal temperatures after 1 week all remained well within manufacturing specification.

So I personally feel that under normal home conditions with a bit of common sense, cabinets are not a death sentence. There would appear to be other factors of greater significance that would have a greater impact on unit life.
 

LV426

Administrator
Staff member
OK guys. Can we all now please DROP the heat/longevity of components/cabinets point. It's gone way beyond the point of the thread and, indeed, way beyond Freeview. The OP seems to have proved that this is magnetism related and nothing to do with heat...............
 

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