BM370 is a small portable single-channel oscilloscope that was produced by Czechoslovak Tesla national enterprise in Brno in the 1960s and 1970s.
It is designed to observe periodic alternating voltages (it does not have a DC mode). Due to its small dimensions, it is intended for repair practice,
but it is also suitable for measurements in the laboratory or in production. The bandwidth of the two-stage vertical amplifier is 5 MHz and the sensitivity
better than 52 mV/cm. In the increased sensitivity mode (input terminal x3), the sensitivity is better than 17 mV/cm, but the bandwidth is reduced to 200 kHz.
The sensitivity can be adjusted with a compensated divider in 7 steps: 1:1, 1:3, 1:10, 1:30, 1:100, 1:300 and 1:1000. The input impedance is 1 MΩ, 30 pF.
The maximum DC component of the input voltage is 400V and the maximum AC voltage is 300V.
The time base with tube E2 works in the range of 20 Hz - 150 kHz in 8 ranges and with continuous adjustment, the synchronization is internal.
BM370 oscilloscope also has an X-Y mode, in which this tube works as a horizontal amplifier with a bandwidth of 10 Hz - 200 kHz and a sensitivity of 500 mV/cm,
the sensitivity can be adjusted with a 100 kΩ potentiometer. The screen has a green glowing circular screen with 7 cm diameter.
This oscilloscope is equipped with potentiometers for brightness control (with a mains switch),
beam focusing, horizontal and vertical shift, continuous adjustment of the time base frequency and sensitivity
in the horizontal amplifier mode (X-Y), and rotary switches for setting the vertical sensitivity and time base (one position for the X-Y horizontal amplifier mode).
BM370 oscilloscope weighs 5.85 kg, dimensions are 140 x 225 x 310 mm. It is powered from a 120V or 220V mains (the selector also has an unmarked position for 230V, see photo below),
the consumption is 30VA.
BM370 oscilloscope is fitted with tubes:
2x EF80 (hf pentode)
1x EF183 (controlled pentode)
1x 6Z31 (two-way rectifier), a version with a solid-state rectifier also existed
1x 7QR20 or DG7-31 (oscillographic CRT with electrostatic asymmetric deflection and focusing, green screen, medium afterglow)
