MIKE ROSS wrote in a message to Matt Mc_Carthy:

 MR> "Matt Mc_Carthy" wrote to "Roy J. Tellason" (04
Nov 02  02:37:09) 
 MR> --- on the topic of "BIRDBOX"

 RJT> Interesting!  Do you have any idea as to what the wavelengths
 RJT> are of these two lights?

 MM> No idea at all.  :-((  I do know the EPROM eraser emits a rather
 MM> bright blue light, somewhat like I'd seen many years ago in
 MM> "sanitizing" equipment.  The fluorescent 'black light'
barely seems to
 MM> emit any light at all, but does really strange things to the
 MM> appearance of different fabrics, dyes, etc.
 MM> .............

 MR> I think eprom erasers use a higher wavelength about 2,500 Anstroms
 MR> and black-light lamps are likely centered at the edge of visibility
 MR> maybe 3,000 to 3,500 Angstroms? Visible light begins at about 4,000
 MR> Angstroms. 

 MM> Shame you can't shine something inside a computer and have all the
 MM> "bad parts" light up for you...   :-))

 MR> Apparently with an IR camera, hot parts show up and cold parts show
 MR> up. The theory being that cold parts are dead... well it works for
 MR> humans! 

Back in the days when I worked on c64s there were a lot of them that came
in with a blank screen,  the most common problem.  This could be due to a
lot of different things,  as pretty much has to be working right before it
gets to the signon screen,  but we always tested the power supply as a
matter of course.  If it was showing unregulated or otherwise incorrect
+5vdc output,  the primary suspect was the ram chips,  because they seemed
to be the most vulnerable to overvoltage.  Easy enough to find the bad ones
with a scope on the data pin.  Or by touching them with your finger in a
lot of cases.  Trouble was,  sometimes they'd get hot enough to burn ya! 
So eventually I found a PTC thermistor in my junk box and wired it into a
probe that'd fit my meter (dual banana plug & all).  And used _it_ to
check those chips first,  before I'd put my finger on them.

Not as elegant as an IR camera,  but one hell of a lot cheaper!   :-)

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