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12A5

Sensibly equivalent to:
CV908
See also:
Impex Radio 12A5 Box
    
Extras ▼

 

The 12A5 has a conventional indirectly-heated cathode but its heater is centre-tapped so that it could be used in (American) car radios suitable for either 6V or 12V systems. Car radios of this era used 'vibrator' HT power packs which were not very suitable for generating HT voltages in the 250-300V region. The 12A5 was therefore designed to operate well from lower HT voltages and therefore needed a 'juicier' cathode to provide extra current.
The Impex logo and the word Foreign.
The dome and top mica components. Note that within the three wire grids are two cathode tubes. Each cathode is threaded with two hairpin heaters making four pass in total per cathode.
The UX7 base pins.
The classic envelope is 38 mm in diameter and, excluding the UX7 base pins, is 91 mm tall.
References: Datasheet & private communication. Type 12A5 was first introduced in 1940.

 

Pin Connections
UX7
1
2
3
4
5
6
7
h
a
g2
g1
k
hct
h

 

Absolute Maximum Operating Conditions
Pentode
Vh
Ah
Va
Vs
Vg
mAa
mAs
ra
gm
Pout
D
6.3
0.6
180
180
-25
48
14
35,000
2.4
3.4W
11%
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated March 02, 2018.
shape:classic construction:pinch type:pentode age:1940.1950 base:ux7 heater:6.3v pins:7 pin:1.h pin:2.a pin:3.g2 pin:4.g1 pin:5.k pin:6.hct pin:7.h
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