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27

Sensibly equivalent to:
UY-227
See also:
National Union 27 Box
    
Extras ▼

 

The type 27 triode is also known as the UY-227. It is an indirectly heated audio valve with a good reputation for performance. This exhibit carries a paper band with the words Quality Approved - Special export test.
With 90 Volts on the anode the grid bias should be -4.5 Volts. At 135 Volts on the anode the bias should be -9 Volts. At the absolute maximum anode voltage of 180 Volts the bias should be set to -13.5 volts. The heater cathode voltage should not exceed 9 Volts.
The carbonised anode can be seen to be stitched together.
The etched identification 27 and Made in USA can be clearly seen.
The working part of the anode is cylindrical and the grid is a wire helix.
The classic envelope is 38 mm in diameter, and excluding the UX5 base pins is 88 mm tall.
References: Datasheet, 3002, 1043 & 1040. Type 27 was first introduced in 1935.

 

Pin Connections
UX5
1
2
3
4
5
h
k
g1
a
h

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
2.5
1.75
180
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated February 11, 2013.
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