Homebrew PCBs

Dave,
What a great idea!  I bet you need a lot of top lighting for it, 
though.  Those things are being blown up at least 20 to one, which cuts 
the apparent brightness 20-1, and then that has to be seen through the 
frosted glass screen, which eats even more light.
I bet a series of 10 to 20  bright white LEDs mounted on the frame, 
pointing to the focal point would provide enough illumination to over 
come the expansion losses and the screen.  3 (or 4) in series powered 
off a mains to 24V transformer with a bridge rectifier halving the V and 
doubling the +V spikes should give you what you need.  You can probably 
get along without current limiting, since the 12V is not much over the 
LED losses, and they are running at only 50% duty cycle.  I've run 
bright white LEDs at 4 volts constant at 100% duty cycle foe extended 
periods:  that's what the cheap 3x1.5V cell 1 LED pocket flashlights 
do.  Internal resistance of the batteries and current draw reduce the 
4.5V to about 4, and you can leave them on forever.
The next question is if the optics are adaptable.  I believe that if it 
focuses on a place, it does not matter much if the light is from the 
bottom or top.
Of course, all this is conjecture, as I have not tried either thing 
yet.  As I think Richard Fienman(sp?) said "Your mileage may vary".
Wait, that was the EPA, Fienman said that it's unlikely that you can 
derive actual behavior from first principals.
Richard

>Message: 9         
>   Date: Wed, 27 Oct 2004 04:12:47 -0000
>   From: "Dave Mucha" <dave_mucha@...>
>Subject: Muicrofiche reader
>
>
>Hi all,
>
>I have a microfiche reader that I was thinking might be used for 
>inspecting PCB's 
>
>Has anyone used one of these with a non-bottom light application  
>like this ?
>
>Any ideas for the use of the thing ?
>
>Dave
>  
>