Poof and my Dedo's blown... again

19 replies [Last post]
noddydog
Offline
Joined: Feb 28 2004

OK, is this just me or does anyone else have issues with bubbles constanly blowing on Dedos? I use a set of DLH4's with 24V 150W bubbles and I've had about four blow (in different heads) over the last 12 months.

Incidentally I don't just pull them out and flick them straight on, I have them faded down and gentle bring them up to full.

Steamage
Offline
Joined: Nov 11 2003

Frustrating, but is this about HD, specifically? You might get more responses in the more general area?

Mark @ Steam Age Pictures - Steam trains on video in aid of railway preservation societies. Latest release: "Mainline 2012, LMS Locomotives", on DVD or Bluray Disc.

noddydog
Offline
Joined: Feb 28 2004

Good point, just saw the word 'Production' tagged on end, but realise it's in relation to HDTV. My bad, however perhaps my saving grace is that Dedo's do work with HD productions:-)

Alan Roberts
Alan Roberts's picture
Offline
Joined: May 3 1999

I;ve no problem with it being here. High-temperature lamps don't last long, however well you treat them.

Get my test cards document, and cards for 625, 525, 720 and 1080. Thanks to Gavin Gration for hosting them.
Camera settings documents are held by Daniel Browning and at the EBU
My book, 'Circles of Confusion' is available here.
Also EBU Tech.3335 tells how to test cameras, and R.118 tells how to use the results.

Dugi
Dugi's picture
Offline
Joined: Jul 2 2009
noddydog wrote:
OK, is this just me or does anyone else have issues with bubbles constanly blowing on Dedos? I use a set of DLH4's with 24V 150W bubbles and I've had about four blow (in different heads) over the last 12 months.
Incidentally I don't just pull them out and flick them straight on, I have them faded down and gentle bring them up to full.

Kind of depends on your usage noddydog.
Four bulbs in a year doesn't really mean much if you don't say how often they're switched on or to what other treatment they're subjected.
I had three Dedos which traveled all over the place with me, chucked in Crew buses, airport baggage handlers etc. but I didn't actually switch them on that much. Each head used 2 bubbles a year, on average.
PS There should never be a problem with "pulling them out and flicking them straight on!" IMHO

Alan Roberts
Alan Roberts's picture
Offline
Joined: May 3 1999

Tungsten filaments fail through evaporation, the metal evaporates. The rate of volume loss is directly proportional to the actual temperature, and that's a function of the current. The resistivity of tungsten has a temperature coefficient, so the resistance goes up as the temperature goes up, so the maximum current goes into the filament at switch-on, it stabilises when the heat loss exactly balances the power input. All of which means that the life-time is much more to do with the number of times you've switched it on than anything else, the number of hours isn't actually very important, it's the power-up cycles that kill it.

Get my test cards document, and cards for 625, 525, 720 and 1080. Thanks to Gavin Gration for hosting them.
Camera settings documents are held by Daniel Browning and at the EBU
My book, 'Circles of Confusion' is available here.
Also EBU Tech.3335 tells how to test cameras, and R.118 tells how to use the results.

Dugi
Dugi's picture
Offline
Joined: Jul 2 2009
Alan Roberts wrote:
Tungsten filaments fail through evaporation, the metal evaporates. The rate of volume loss is directly proportional to the actual temperature, and that's a function of the current. The resistivity of tungsten has a temperature coefficient, so the resistance goes up as the temperature goes up, so the maximum current goes into the filament at switch-on, it stabilises when the heat loss exactly balances the power input. All of which means that .......................

Oh Alan, please send me a Christmas card.
As it is, I can only dream of the verbiage.

Alan Roberts
Alan Roberts's picture
Offline
Joined: May 3 1999

Words are important, they convey meaning, usually :D

Get my test cards document, and cards for 625, 525, 720 and 1080. Thanks to Gavin Gration for hosting them.
Camera settings documents are held by Daniel Browning and at the EBU
My book, 'Circles of Confusion' is available here.
Also EBU Tech.3335 tells how to test cameras, and R.118 tells how to use the results.

H and M Video
Offline
Joined: Jun 5 1999
Alan Roberts wrote:
Words are important, they convey meaning, usually :D

Alan, could you send this quote to Vince Cable:D

Harry

PC Specialist 3Gz Dual Core, Premiere CS3, Encore CS3, After Effects CS3, Matrox RT.X2, Panasonic HD HS-300, Z1E & PMW-EX3 Cams.
 
Now with a PC Specialist Quad Core i7-3770, 16GB RAM, 180GB SSD, GeForce GTX560 Ti Graphics Card, Blu-Ray & DVD R/W Burners and can't wait to set it up. Now up and running.  What a difference in Blu-Ray footage.

Alan Roberts
Alan Roberts's picture
Offline
Joined: May 3 1999

Far be it from to me advise politicians, they're the experts :)

Get my test cards document, and cards for 625, 525, 720 and 1080. Thanks to Gavin Gration for hosting them.
Camera settings documents are held by Daniel Browning and at the EBU
My book, 'Circles of Confusion' is available here.
Also EBU Tech.3335 tells how to test cameras, and R.118 tells how to use the results.

MAGLINK
Offline
Joined: Mar 8 2007
Alan Roberts wrote:
Far be it from to me advise politicians, they're the experts :)

In the style of Alan Partridge: OFCOM-BRIBE-TASTIC!:D

rone01
Offline
Joined: Feb 9 2009

We hardly every blow our Dedo Bulbs (150) - are all the heads blowing?

Have you tried a different batch/brand of bulb?

Red EPIC / Scarlet - Panasonic AC 90 -  besq.co.uk

Alan Roberts
Alan Roberts's picture
Offline
Joined: May 3 1999

We had (in BBC R&D) a batch of Redhead bubbles that each lasted only a few hours. The next batch were fine. It could be just a poor batch.

Get my test cards document, and cards for 625, 525, 720 and 1080. Thanks to Gavin Gration for hosting them.
Camera settings documents are held by Daniel Browning and at the EBU
My book, 'Circles of Confusion' is available here.
Also EBU Tech.3335 tells how to test cameras, and R.118 tells how to use the results.

noddydog
Offline
Joined: Feb 28 2004

On average the bulbs are lasting a few hours, probably no more than 5-10 at a guess. It could be a batch, I've just ordered some more so I guess I'll find out in due course.

Right now I am using Philips bubbles, not sure who else makes them for the DLH4?

On a connected (but different note) can anyone tell me whether the colour temperature stays the same on Dedo's as you dim them as it does with Kino Flos?

Dugi
Dugi's picture
Offline
Joined: Jul 2 2009

Lasting only a few hours is not right at all....Some'it up there. I've shot interviews with Dedos that have lasted much longer than that.
They will get warmer (colour temp.) as you dim them.

Alan Roberts
Alan Roberts's picture
Offline
Joined: May 3 1999

Kinoflo are fluorescents, so the colour of the light you get is down to the chemistry of the phosphors inside the tube, and nothing to do with the excitation level.

Dugi's right in that the CCT of a filament goes down as the current goes down. There's a rather wonderful formula for this, derived by Max Planck, which goes into quantum mechanics, but I won't bore you with the details. However, as the filament slowly evaporates, it does so from the hottest parts, the gaps between the supports, and so becomes uneven in diameter. This accelerates quite rapidly towards the end, because the thinnest parts have the highest resistance and so have the highest power consumption, until one of the hottest points reaches 3680K, when it melts, and poof ...

Noddy, have you the means to measure your mains voltage? The higher the voltage, the shorter the filament life. In theory you should expect 230volts, but the tolerance range (+10% to -6%) means that anything from 216 to 253 is legal, I get 252 volts these days, I've only a few feet from the village transformer on a pole in the next field, and tungsten lamps last no time at all, which I why I use mainly fluorescents.

Get my test cards document, and cards for 625, 525, 720 and 1080. Thanks to Gavin Gration for hosting them.
Camera settings documents are held by Daniel Browning and at the EBU
My book, 'Circles of Confusion' is available here.
Also EBU Tech.3335 tells how to test cameras, and R.118 tells how to use the results.

noddydog
Offline
Joined: Feb 28 2004
Alan Roberts wrote:
Noddy, have you the means to measure your mains voltage? The higher the voltage, the shorter the filament life. In theory you should expect 230volts, but the tolerance range (+10% to -6%) means that anything from 216 to 253 is legal, I get 252 volts these days, I've only a few feet from the village transformer on a pole in the next field, and tungsten lamps last no time at all, which I why I use mainly fluorescents.

Interesting point Alan, your comment reminded me that 70% of my Dedo use is out in Asia, more recently Thailand, Singapore, Malaysia and Indonesia.

I suspect the old 'tolarance range' won't be having a good day in some of those places:-)

... so maybe that's my problem!

Alan Roberts
Alan Roberts's picture
Offline
Joined: May 3 1999

Well now, if you'd mentioned that at the top of this thread, I'd have said it immediately. Almost certainly, that's the problem. Next time you travel, use some form of in-line dimmer, that way, you can bring them up to power gently rather than simply switching on, that alone should double the bubble life.

Get my test cards document, and cards for 625, 525, 720 and 1080. Thanks to Gavin Gration for hosting them.
Camera settings documents are held by Daniel Browning and at the EBU
My book, 'Circles of Confusion' is available here.
Also EBU Tech.3335 tells how to test cameras, and R.118 tells how to use the results.

Dugi
Dugi's picture
Offline
Joined: Jul 2 2009
Alan Roberts wrote:
Next time you travel, use some form of in-line dimmer, that way, you can bring them up to power gently rather than simply switching on, that alone should double the bubble life.

Ahem!
Post #1 - "Incidentally I don't just pull them out and flick them straight on, I have them faded down and gentle bring them up to full."

Alan Roberts
Alan Roberts's picture
Offline
Joined: May 3 1999

Yeah, I realised that when I'd posted, but the point is valid anyway.

Get my test cards document, and cards for 625, 525, 720 and 1080. Thanks to Gavin Gration for hosting them.
Camera settings documents are held by Daniel Browning and at the EBU
My book, 'Circles of Confusion' is available here.
Also EBU Tech.3335 tells how to test cameras, and R.118 tells how to use the results.