What's 6Z-P1??
What's 6ZP1?
6Z-P1 is a famous Japanese power pentode tube, designed for audio output
stage of cheaper radio receiver.
The outline is ST-12 glass type tube with
small shell six pin, called a UZ base in Japan. The electrical characteristic is
similar to type 38 output tube, except for a heater current rating 0.35A (a
heater power 2.205W) and a high mutual conductance.
This is the cheapest
tube to be able to obtain 1 W audio output power with a higher sensitivity than
American type 38, under a lower electrical power consumption than types 41 and
42.
6Z-P1 was developed during 1945-1946 as a 6.3V version of 12Z-P1 which was
developed by Tokyo Electric Co. (Toshiba) in 1939, as an output tube of Japan
standard transformer-less radio receiver. It was used in 1950s mainly for the
cheapest radio receiver named the Popular Type*. Furthermore, it was often used
in an audio amplifier as a pinch hitter of American type 42 and in a small Ham
radio transmitter as a final tube.
It was said that a certain Ham guy had
succeeded in the experiment to obtain a 10W output from 6Z-P1 amplifier using
water cooler. 6Z-P1 had been manufactured until 1980's as a spare part of radio
receivers.
* A deluxe receiver that used the American pentode 42 was called the "standard" type radio receiver. Furthermore, the highest one used 2A3.
6W-C5
6W-C5 is a Japanese penta-grid frequency converter tube.
Outline is a
ST-12 glass type tube with small-shell and seven-pin, which is called Ut base in
Japan. Electrical character is the same as US 6SA7/6SA7GT, except for heater
power of 6.3V and 0.35A (2.205W).
Several years after the second world war,
status of electricity supply was not so good. The oscillation-stop in the
superhet receiver using old 6A7 converter was often observed, when the line
voltage drop. Therefore, a new converter 6W-C5 was developed by Toshiba in 1947,
as a special version of American 6SA7 with a strong heater to avoid such
oscillation-stop.
Another important feature is that 6W-C5 has an outline of the old ST type. It means that each tube-company could use old mass-production machines for manufacturing a new 6W-C5.
The common feature of 6Z-P1 and 6W-C5 is the heater power 0.35 A, which has a
strange value, compared with American tube standard 0.3 A.
The reason
WHY??
This extra heater power 16 % was useful to keep the emission of tube
against the AC line voltage drop, observed under the poor power supply system in
several years after the war.
6Z-DH3A
6Z-DH3A is a single diode single triode tube for detector and audio amplifier
of radio receiver.
The outline is ST-12 glass type tube with Japanese UZ
base. This tube was developed as an economical version of American type 75,
which removed one of twin diodes. Therefore, the electrical characteristic is
the same as 75 and 6SQ7.
First, a top grid version 6Z-DH3 and a 12V single
ended version 12Z-DH3A were developed by Toshiba in 1947, then 6Z-DH3A as the
6.3V version was developed by NEC in 1948.
The Japanese original 6Z-P1, 6W-C5 and 6Z-DH3A were used for Japanese popular/standard radio receivers until the end of 1950s. Typical tube lineup for the popular type of Japanese super-heterodyne radio receiver was 6W-C5, 6D6, 6Z-DH3A, 6Z-P1 and KX-12F, and another lineup for the standard type was those replaced with 42 and 80.