Re: Blue phosphor scopes

Richard Knoppow

The original P1 was a distinctive green. The later, burn resistant, phosphor was a bluish green. There is a PDF chart showing all the CRT phosphor characteristics at:

    And other places, a Google search will find them.

On 6/26/2020 7:18 AM, Harvey White wrote:
The dual layer phosphor was a P7, IIRC, where the inner layer was blue and the outer was yellow, long persistence.  The blue layer excited the yellow one.  There was an orange phosphor I had one of, once, a P12 I think.  Moderately long persistence.  P11 was blue only.  The film for recording was othochromatic, not panchromatic, so no red sensitivity and could be developed in a standard darkroom under red light.

You'd have found P7 used in radars during WWII.

The original oscilloscope phosphor was a P1, I think, green. Tektronix may have invented another one, a similar phosphor much more resistant to burning.  P4 was the white TV phosphor, btw., and I think that P31 was the tricolor TV tube phosphor.

I once had a 513D with a P11 phosphor, and I think the 512 I had used a P7.  Not sure where the P12 was at the time.

For a real oddity, there was a phosphor (calcium carbide?) that did not glow, but darkened with electron exposure.  It was permanent unless erased with a hot iron.


On 6/26/2020 2:51 AM, Richard Knoppow wrote:
Do you mean pure blue?  There were some phosphors that had blue fluorescence and yellow or orange phosphorescence. Generally the blue was very fast decay and the yellow or orange long decay. A filter over the screen could be used to choose the color wanted. There were also very fast decay blue phosphors used for Kinescope recording tubes. In this case the film used was color blind.

On 6/25/2020 10:19 PM, Reginald Beardsley via wrote:
Did anyone other than Tek make scopes with blue phosphors?  I was chatting with a friend and neither of us could think of anyone.  All either of us had seen was green CROs.

Have Fun!

Richard Knoppow

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