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Re: HiRes 1440 - Questions





On Thu, 6 Apr 1995, David L. Tosh wrote:

> I think the underlying idea of a master telecine transfer format has some
> merit but I have some questions that arise from my understanding of this
> specific proposal.
> 
> 1. The modified, flat to 12 MHz rank must be an analog (non URSA, or Gold)
> model. The modifications include the usual tweaks plus an increase of the
> CRT high voltage. I wonder what the X-Ray output of the tube becomes and
> what the regulatory agencies think of that modification. I _don't_ want to
> stand in front of that machine.
> 
> David Tosh  dlt at earthlink.net  (CIS 72167,1376)
> 
> 
> 
I shared your concerns about the x-ray output of the crt at 30kv.  There 
is an A.O.T. resistor on the 1010 eht board chosen specifically to prevent 
the high voltage from exceeding 29kv because of increased x-ray output.  
While at NAB, Seth Adams related that above 27kv, the x-ray output of the 
crt increased to the 11th power of the increase in voltage (!).  I also 
spoke with Craig Risebury at Rank's booth about this (Craig is the design 
group leader for Rank's hi-res machine).  Turns out they also run their 
crt at 30kv on the hi-res.  They have a radiation meter in the lab, and 
the crt still puts out less x-ray radiation at 30kv than a luminescent 
watch, due mainly to the fact that the Brimar crt glass is leaded.  They 
do add additional shielding around the crt "just to be on the safe side."
Tube Enhancement crt's also have leaded glass.  This is probably standard 
practice in the crt biz.  Dave Walker of DAV (Digital Deflection) said he's 
going to do some testing of his own for his own peace of mind.


--Ralph Edwards