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4-THA

Sensibly equivalent to:
A36C AC/TH1 CV826 TH4A TH4B
    
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The 4-THA is a triode hexode frequency changer designed for AC sets that were fitted with mains transformers, for AC/DC (universal) sets the functionally identical 203THA with a 200 mA heater (for serial heaters) was also issued.
The triode is employed as the local oscillator and the hexode for the mixing process, the input signal being coupled to the control grid via the top cap for maximum separation of the circuits.
The top cap connection to the copper supports of the hexode. Th screen grids are strapped together at the top.
The pinch with the rest of the structure hidden by the coating.
Using the microscope the rectangular cathode, triode grid and multi pass heater can be seen.
The classic envelope is 44 mm in diameter and, excluding the B7 base pins, is 119 mm tall.
References: 1043. Type 4-THA was first introduced in 1938.

 

Pin Connections
B7
1
2
3
4
5
6
7
tc
a(t)
g1(t),g3
g2,g4
h
h
m,k
a
g1

 

Absolute Maximum Operating Conditions
Hexode
Vh
Ah
Va
Vs
Vg
mAa
mAs
gm
4.0
1.5
250
100
-2
3.5
5.5
0.85

 

Absolute Maximum Operating Conditions
Triode
Va
mAa
100
1.5
Updated May 21, 2021.
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