5 inch panel

[slick69]

Hello wondering if I could get some advice I have 2 OHP both 3M both going one I,m gutting the other I plan to use complete.The question I will be using a portable DVD lcd I,ve cut a ply panel to cover the OHP panel and will cut out LCD panel size dead center will this work.Below is the specs of DVD hoping for around 40 inch screen?
4:3 TFT ACTIVE MATRIX 5.6” LCD SCREEN RESOLUTION 400 (RGB) BY 234.
COMPOSITE OUTPUT/INPUT, S VIDEO OUTPUT, COMPOSITE INPUT
TWO CHANNEL DOWN MIX OUTPUT/INPUT TERMINAL, BUILT-IN TWO CHANNEL STEREO SPEAKERS, INCLUDES HEADPHONES
DTS/AC-3/PCM OPTICAL OUTPUT
AUDIO 24 BIT/96KHZ.VIDEO 10 BITS.

[Guy Grotke]

That should work, but the problem you will have is that the small LCD screen will only get about 1/4 of the light from the bulb. So it will not be very bright.

You could try adding a precondensor lens right at the bulb to bend the light just to the middle of the OHP fresnels. Then your LCD would get a lot more of the light you are paying for.

Most OHPs make a 10' diagonal image from a transparency page from about 10' away. A 5 inch LCD would scale down to about 47" diagonal from 10 feet. Adjust the throw distance to get different size images.

[slick69]

Could I use the curved lens from one of the projector heads is that the same lens and mount it infront of the bulb.Also would a reflector behind lens help?

[Guy Grotke]

No, if you have a pair of big lenses in the OHP head, then they are probably about 660 mm focal length (fl). For a precondensor lens you need a much shorter focal length lens. More like 200 mm fl. It depends on how close you can get it to the lamp. You can expeiment with a strong magnifying glass. Point the lamp toward a wall or white paper a couple of feet away. Then move the magnifier right up to the lamp. You will see it make a cone of bright light, projecting a circle. You want that circle to be 6" diameter at the distance your OHP fresnels sit from the lamp. (ie. 200 to 240 mm)

You also need to make sure the precondensor lens doesn't overheat. Maybe add a fan just for it.

[slick69]

OOPS Allready mounted it right in front of the light guess its removal and try again.As per previous do you think I should use a reflector behind light.

P:S Your input is reall appreciated thus far thanks

[Guy Grotke]

If you are using an original OHP lamp, then it probably has a reflector built in to the bulb glass. Adding another reflector would do nothing for you.

If you are using some other kind of lamp, that emits light toward the bottom of the OHP box, then a good spherical reflector could double your light output. It has to be a section of a very good sphere, and the bulb filament or arc has to be placed right at the center of curvature of the partial sphere. Some people use shiney soup ladels, mixing bowls, etc. and other spend a few more bucks and get a real optical spherical reflector. The very best are called "cold mirror" or "dichroic". They let heat pass through the reflector, and just reflect the visible light. So they don't contribute to overheating the bulb.

[slick69]

Well I,m back again managed to pick up another portable dvd this one has a wide screen (first one I broke the ribbon) DOH my question is I have stripped the dvd with success mounted it on a panel and then onto the OHP the display menu comes on but when I switch it to A/V out, the screen just rolls.I am not using the original power supply and the one I am using has a lower current output will this cause the screen to roll if I dont have enough juice? Also tried a PC power supply with higher current output but same deal.

Any ideas?

[ancorp]

Hmm... define screen rolls... maybe show a pic if possible. If you mean like lines or bands of lighter/darker parts roll accross the screen, than you probably have a ground loop issue, plug the source into the same plug as the dvd player. If not - no idea

Cheers,
Alex

[slick69]

Its just like the vertical hold on a TV theres a clear picture it just rolls there is as you know no vertical hold adjustment.There was a wire going from the metal casing that the lcd sits in to one of the boards could this be a ground?????