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35W4

Sensibly equivalent to:
HY90
See also:
Brimar American Miniature Valves Advert, November 1950 - Brimar 6BE6, 6BA6, 6AT6, 6AQ5 & 6X4 12BE6, 12BA6, 12AT6, 35L6GT, 35W4, 6AK6, 1S5, 1U5, 3S4, 3V4, 1R5 & 1T4 Advert
    
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The 35W4 is a half wave rectifier designed for use with a 150 mA heater chain. The heater is tapped to allow a panel lamp to be incorporated in the circuit.
Thanks to Alex Hiley for this detail on the pilot lamp. Quite wierdly, from a UK viewpoint, the heater is tapped at about 7.5v and the tap can be used to feed a scale light.
If the radio has a scale lamp then the mains live feeds into the light bulb and the pin 4 end of the heater. The other end of the bulb, and the heater tap (pin 6), connect to the rectifier anode. The other end of the heater, pin 3, connects to rest of the series heater chain and carries 0.15A. The section with the bulb across it carries the full mains current, i.e. 0.1 A AC plus the 50Hz current pulses into the anode of the rectifier. Once the set has warmed up there is about 0.3A RMS which splits into 0.15A for the bulb and 0.15A for the pin 4 to 6 section of the heater.
The reason for this arrangement is that if the bulb was put in the series heater chain it would blow at switch-on because of the high surge current into the cold heaters. This arrangement means the bulb is shunted by a cold heater and so protected. The HT current comes up slowly so the lamp current ramps up gently too. This valve lineup, called the 'All American Five', resulted in a very cheap radio. No mains transformer, no series dropper resistor in the heater chain (the heaters add up to about 120v), no thermistor to protect the bulb. The drawback is that if the bulb blows then the 35CW4 won't last many months before it blows too.
The protective minimum series resistance has to be 120 Ohms and the rectifier will feed a reservoir capacitor of 40 μF maximum.
The anode plate has additional side fins for maximum cooling.
The thin glass tube envelope is 17 mm in diameter, and excluding the B7G base pins is 57 mm tall.
References: Datasheet, 3002 & 1040. Type 35W4 was first introduced in 1946.

 

Pin Connections
B7G
1
2
3
4
5
6
7
-
-
h
h
a
hct
k

 

Absolute Maximum Operating Conditions
Rectifier
Vh
Ah
Va
mAa
35
0.15
250
100
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated February 05, 2013.
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