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SP55R

 
See also:
Shortpath Construction - Cosmos SP55R Box
    
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The Cosmos SP55R from Metrovick was introduced in the period 1926-1928. The filament is for 6.0 Volt operation and the SP55R was designated for audio output service in radio receivers. The amplification factor or μ is 6.
The SP or Short Path refers to the construction method that enabled the grid to be set closer to the filament than conventional cylindrical designs.
A close-up of the top of the electrode assembly shows the flattened nature of the construction and that the bright grid is wound on a single notched rod.
In profile the approx 2 mm thick anode cavity is clearly seen.
The valve came with a set of operating conditions and the four pages are reproduced here.
On the second page the operating points for various duties are given
A full graph is given.
The back page has the Metrovick logo.
The balloon envelope is 50 mm in diameter and, excluding the B4 base pins, is 99 mm tall.
Reference: 1043.

 

Pin Connections
B4
1
2
3
4
a
g1
f
f

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
Vg
mAa
ra
gm
6.0
0.25
120
-4
10.0
3500
1.70
Updated April 30, 2013.
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