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EMV backlight repair manual

ALSC Archive » Electrical » Archive through May 04, 2005 » EMV backlight repair manual « Previous Next »

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Archive through August 11, 2002Tony Chen23 8-11-02  11:15 pm
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Tony Chen (Tchen)
Posted on Sunday, August 11, 2002 - 11:18 pm:   Quote Highlighted Text

Barry Anderson (Baron)
Posted on Monday, August 12, 2002 - 9:34 am:   Quote Highlighted Text

Tony, it also looks like you need English EMV Button stickers!
Harry Lemmens (Hrl)
Posted on Monday, August 12, 2002 - 11:10 am:   Quote Highlighted Text

Barry, when I get my own EMV unit out, I am going to backfill the plastic, and then engrave the button faces with English text. However, I have access to an engraver. (A large pantograph with a motor and engraviving head, allows you to trace out characters very easily.)
Barry Anderson (Baron)
Posted on Monday, August 12, 2002 - 7:08 pm:   Quote Highlighted Text

Good luck, and are you coming to the Wantirna Pub to meet Wayne???
Luke David
Posted on Friday, April 30, 2004 - 7:26 am:   Quote Highlighted Text

Has anyone ever found a part number for a suitable backlight tube for the EMV (can't find anything using the search). I have an EMV for repair someone minus its original tube AND inverter circuit and without other backlight bits. It has been replaced by 4 tubes and 4 invertors - 3 of each have failed.
Dominik Bloemhard
Posted on Friday, April 30, 2004 - 9:02 am:   Quote Highlighted Text

If all else fails, you can grab the backlight out of one of the cheapie 5.6" screens you see on the net. I have a broken one at home, and its exactly the same size as the original screen...
Harry Lemmens
Posted on Friday, April 30, 2004 - 10:52 am:   Quote Highlighted Text

I would be tempted to try about 50 white LEDS to replace the CCFL tubes in this case. Because the white leds tend to be well focused you may need an extra diffuser, or perhaps grind the front face of each led to defocus the light.

The ones that have been modified in this area are always going to be harder to repair! (I have seen another that someone had chopped out the original inverter.

The other option is to replace those tubes with Jaycar white CCFLs and inverters. The Jaycar tubes did not seem particularly bright though, so I don't know how effective this may end up being!

(White LEDs on the other hand seem extremely bright! The 24 volt supply that originally ran the inverter may still be intact as well, which would allow you to put 5 or so leds in series using just one resistor as a current limiting device. I would program the LEDs for as much current as the spec sheet says they will continuously operate for.

(I see Vishay have some VERY bright LEDS with a +-50 degree beam width that operate with 50mA continuous current, but have a voltage drop of 5.4 volts (max), so you could only put 4 in series off the 24 volt supply! (Looks like they require some heatsinking as well!)

See Vishay White LED data for a list of the various white LEDS from Vishay.

Obviously there are several other manufacturers of white LEDs, so it might pay to look around if you go down this path.
Miles Baker
Posted on Friday, April 30, 2004 - 11:09 am:   Quote Highlighted Text

A guy I was buying some parts off had 4 pin LEDs in stock. I bought a bunch of red ones to make a tail light for a buddy's motorbike. He said they are 72 degree viewing angle. Whites are $2 each, reds are $1 each. I believe they were quoted at "about 3000mcd". The brightness is pretty good on the reds. A dozen made a bright tail light. Not sure about the whites, but the reds are 2V 40mA.

I think he had other colors.. red, yellow, green, blue, white. I would imagine the red and yellow would be the $1 ones and the rest are $2. Bad news is, minimum buy was 25. I still have the rest of the reds lying around.
Harry Lemmens
Posted on Friday, April 30, 2004 - 11:38 am:   Quote Highlighted Text

They sound like the ones at the bottom of the Vishay list. They are rated at up to 4200 mcd ("F" prefix). The total included angle is 125 degrees, but are down to 1/2 intensity at 45 degrees. Although the colour temperature is quoted at 5500 degrees K (which is a little low for the display) I suspect it will not matter. (Every white LED I have seen has a massive peak in the Blue region, which may well compensate nicely as a LCD display back light.)

The other thing is, it may be possible to go direct to a supplier for 50 type quantites, which does tend to drop the price substantially. (Suppliers minimum quantity will also be a tube)

Using those, I estimate about 50 would illuminate the entire LCD fairly effectively. In fact, I wouldn't be suprised if the LCD was much brighter than a stock unit when using these LEDS! (PS: I see the Vishay doco says they are packed in tubes!)

And yes, the four legged LEDs are plainly superiour in light intensity to the rest of the pack! Especially when looking at the lights angle!
Richard Warland
Posted on Saturday, May 01, 2004 - 4:45 pm:   Quote Highlighted Text

Has anyone tried Farnell Electronics. They sell CCFL plastic sheets that can be cut to size and connected to a standard inverter. Dont know how bright the stuff is tho. Check their website for details
Neil Griffiths
Posted on Saturday, May 01, 2004 - 6:07 pm:   Quote Highlighted Text

Steve Taun has had some Fluros made up that are Identical to the Factory ones...Yous will also notice the Heater element on the Fluro...Thats why it dont Blink on startup like a Fluro normally does...
Luke David
Posted on Saturday, May 01, 2004 - 6:15 pm:   Quote Highlighted Text

A quarter VGA light panel was tried Dom, but itís not very bright. The original inverter cct has also been removed by the previous repair.

Farnell don't do the W shape tube that is required, so you then start to get back to what has been put in my picture above - its just that 75% of tubes and invertors are stuffed.

There are some very nice 5watt Leds available now but require heat sinking and are £8 a go + they require 5 volts, so 9 Leds would/may be required.
Harry Lemmens
Posted on Saturday, May 01, 2004 - 7:22 pm:   Quote Highlighted Text

Neil, I tried several lamps that were not heated, and all started instantly ... Its got to do with the design of the high voltage inverter. The heating on the original is to rapidly get the lamps to a reasonable operation temp. A lot of flouro's are not very bright until they warm up. (Like a 10:1 reduction in output when they are at 0 degrees celsius). None of the variations I tried even came close to the original tube in terms of intensity, and also the colour temperature of the original light. Even the 6000 degree kelvin tubes I tried looked decidedly red (and therefore "dull") by comparison to the original tube.

When I had the original backlight inverter working in the first EMV I fixed, I did succesfully have 4 domestic lighting tubes in "parallel striking simultaneously. (The tubes had heated cathodes, but I did not bother with the heaters. The HV inverter circuit will still strike these tubes without requiring the "Cathodes" be heated!) I did however, put 100 Ohms in series with each tube. (the 100 ohm resistor doesn't get hot (not much loss), but forces the tubes to share the current between them.)

Luke, the LEDs in the Vishay link are available in Aus for around $2 a pop, so it might cost $100 in leds. (If you notice, the Vishay leds application data state that one of this LEDs uses is LAMP replacement!). 4 inverters and 4 tubes may also cost around $100 or more ... I would be going for the leds. I feel certain that the diplay would actually look much brighter using the LEDs to backlight the EMV's LCD.
Luke David
Posted on Saturday, May 01, 2004 - 8:34 pm:   Quote Highlighted Text

Ok fine on the LEDs Harry, I have some of those mounted in the lens of an RS 369-3829 - great on the bike at night.
I was meaning the Luxeon types available form RS etc (example RS 449-1797).
Neil Griffiths
Posted on Saturday, May 01, 2004 - 9:58 pm:   Quote Highlighted Text

Hazza..Colored LEDS to make the screen Pretty ?? heheheheeh
Luke David
Posted on Tuesday, May 04, 2004 - 8:22 am:   Quote Highlighted Text

Just to add, both the tube and the metal cased inverter circuit had been removed from the above.

4 separate invertors, mounted in an old Soarer TV Tuner box (fitted up above the brake pedal) had be used to power the tubes.

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