Touchscreen Fade

[Cotswold Pete]

This is more of an observation, rather than a fault.

Noticed more readily on these colder mornings that when the Touchscreen comes on at start-up it is suffering from low contrast (or colour fade). 

After about 10 minutes driving the colours and contrast are strong.

All functions work, and I am wondering if this is just the fact that the panel is now 20 years old and the Liquid Crystals are slowly giving up, or whether it is likely that some voltage regulator for the panel is slowly giving up or strugglnig when ambient tempature is low and one day will decide to not light up the panel.  It is a long time since I understood the mechanics of the lifetime of LCD displays, and my 23 year old spare room LCD TV is still going (but very faded)

Any comments or thoughts appreciated.

 

[Britprius]

1 hour ago, Cotswold Pete said:

This is more of an observation, rather than a fault.

Noticed more readily on these colder mornings that when the Touchscreen comes on at start-up it is suffering from low contrast (or colour fade). 

After about 10 minutes driving the colours and contrast are strong.

All functions work, and I am wondering if this is just the fact that the panel is now 20 years old and the Liquid Crystals are slowly giving up, or whether it is likely that some voltage regulator for the panel is slowly giving up or strugglnig when ambient tempature is low and one day will decide to not light up the panel.  It is a long time since I understood the mechanics of the lifetime of LCD displays, and my 23 year old spare room LCD TV is still going (but very faded)

Any comments or thoughts appreciated.

 

This is caused by the cold cathode tubes used to illuminate the screen getting tired. It is normal for these tubes "a type of florescent tube" to have reduced light output when cold, but they do loose output as they age, and eventually stop working.
Be aware the voltage used with these tubes particularly when they are first turned on is high, and can give a nasty shock.

John.

[Cotswold Pete]

3 hours ago, Britprius said:

cold cathode tubes

I assume that they would be a standard type from back 20 years ago, that when they do go might be possible to source.

Also assume more modern systems are LED backlit, so will fade as well, but over a longer period.

 

[Britprius]

2 minutes ago, Cotswold Pete said:

I assume that they would be a standard type from back 20 years ago, that when they do go might be possible to source.

Also assume more modern systems are LED backlit, so will fade as well, but over a longer period.

 

It still surprises me but even in much equipment from today cold cathode tubes are still used. The problem being LED's do not like to be run dimmed over long periods of time. Contrast is adjusted by altering the LCD, but brightness is adjusted by dimming the light source.

John.

[ambermarine]

5 hours ago, Britprius said:

This is caused by the cold cathode tubes used to illuminate the screen getting tired. It is normal for these tubes "a type of florescent tube" to have reduced light output when cold, but they do loose output as they age, and eventually stop working.
Be aware the voltage used with these tubes particularly when they are first turned on is high, and can give a nasty shock.

John.

Are we saying over time unused or used I bought a replacement audio visual A/C centre console as a precaution when I bought my Mark 4 and it is sitting patiently in a sealed container waiting to replace if needed the one that was in the car when new.

The price for it was £40 and the new price was £5K it came off a 40k miles write off and I think the seller assumed it could'nt be used as it had no code but it can be started then re-coded with the switch dance and to that end was a steal.

[BigBoomer]

LCDs are back-lit by Cold Cathode tubes, Electro-Luminescent Panels, or LEDs.
All will under-perform when cold, but the first two are particularly affected by temperatures under 5C.

[Cotswold Pete]

On 1/14/2020 at 5:40 PM, ambermarine said:

and to that end was a steal.

Just done a bit of reading, and Cold Cathode are long lasting, but as we know will have fading output.

Lifetime figures for CCFL is up to 20,000hour plus, before they will not work. (about the same as LED - LED output fades over time as well)

Like any system not being used there will be some degredation, (I assume the gas will leak out of the tube over time - as no lighting system is impermeable)

Doing a quick calc, based on my time in car per year, and the age of the car, the display will have been on for around 8000 hours minimum.

 

So Phil that steal is likely to be a useable or sellable item at  some point

[i-s]

LEDs actually love the cold - they'll last forever if you keep them cold! It's heat and brightness that kill white LEDs. They're fine run dimmed (lower current). 

A few years ago we bought my mother-in-law a cheap LED TV, and 5 years later it was so dim.... But it's on almost 24/7. However, that was a cheap TV, and LEDs have improved since then. 

 

[Cotswold Pete]

31 minutes ago, i-s said:

LEDs actually love the cold

I had forgetten that, and then it reminded me of this

Dyson £££ LED light

They say they should last around 110,000 hours, but I am not sure it would fit behind the touchscreen😶

[BigBoomer]

3 hours ago, i-s said:

LEDs actually love the cold - they'll last forever if you keep them cold! It's heat and brightness that kill white LEDs. They're fine run dimmed (lower current). 

True enough, but within limits. If you go to extremes of cold they can dim and even fail altogether.
LEDs do actually dim when they get hot. This is why higher powered ones have big heatsinks or cooling fans.

The external LEDs used on modern aircraft have a heater circuit to keep them above -10C
Most semi-conductors are designed to operate over a reasonable temp range but very few can handle the extremes of temperature we get on the surface or in the air of our planet.