Category Archives: 5U4S

Finalizing the 6S45P Part four

The simplest amplifier obsession Part 0
Breadboard amplifier Part 1
Chassis building Part two
Assembling the 6S45P amplifier Part three
Finalizing the 6S45P Part four – this one

After having played the 6S45P for a few days I decided to try to improve hum by rewiring the heater and signal wires and reworking the star ground system. I ran the heater wires along the wall, and stretched two coaxial wires directly to the sockets, across the inside of the amp, Taking care to cross other wires at close to 90 degrees. This reduced hum somewhat, but it was still present.

The next step was to rebuild the power supply on a tag board. This would eliminate the ground plane on the PCB and create a cleaner single ground point to chassis.

This is a developing story – sorry for not posing it completed


5Ц4С /5U4S – russian rectifier tube data

 It is commonly assumed that the Russian 5Ц4С (5U4S) rectifier is equal to the western 5Z4G, and its true! The only difference compared to a vintage Brimar is a slightly higher peak inverse voltage at 1400v in stead of 1350v for the 5Ц4С.
The GZ30 is also an equivalent with the same specifications as 5Z4G. Jogis Röhrenbude has a PDF with a scan of an original datasheet. Another datasheet is availible from

There is some confusion concerning the names of this tube.
The Cyrillic letter
Ц looks similar to Latin U but is pronounced Ts like in “cats”
The Cyrillic letter C is identical to Latin C but is pronounced Es like in “escape”
The tube is translated as 5U4C or 5U4S but should be called 5TS4S.
It is not equal to the western 5U4G

5Ц4С rectifier, double-anode tube

(This data is based on google translate and cleaning up the text to some degree. Please suggest better translations.)

Main dimensions of the lamp 5TS4S


5Ц4С valve/tube is designed for rectification of alternating voltage of industrial frequencies. It is used in rectifying devices of various radio equipment. Can be used for rectifying the AC voltage up to 400 Hz. The oxide cathode is indirectly heated. The tube works in any position. The service life is, according to specifications, at least 500 hours. It has 4 pins in an octal socket with a key.

I have found a test of rise time for 5Ц4С. After a cold start  for 0-4 seconds there is no anode voltage, after 4 to 9 seconds rising anode voltage. 10 seconds full anode voltage. Does anyone have rise time data for the 5Z4G or GU30? – please post a comment if they differ.

Voltage drop data have been difficult to find. Generally it is 10-15% of the anode voltage. If you know how much voltage is dropped over the tube please leave a comment 🙂

NOTE!:¨There is a discussion on DIYaudio about the validity of the anode resistance value presented in the table below. A required resistance in the anode circuit of 4.7Kohm is much to high for normal  powersupply duty, for instance in tube amplifiers.
If anyone has used this tube and has practical knowledge of the correct value please leave a comment.

Rated electrical data

  Heater voltage, V 5
  Variable effective stress of the secondary winding of the transformer, V 2х500 
  Resistance in the anode circuit, Ohm  4700 
  Capacitor filter, uF 5 
  Heater current, A 2 
The rectified current, mA 122 
The rectified current when the heater voltage 4.5 V, mA 100 

Maximum electrical quantities

  Most heater voltage, V 5.5 
  The smallest heater voltage, V 4.5 
  The greatest amplitude of the reverse voltage of the anode, in 1350 
  The highest average value of the rectified current, mA 125 
  The greatest amplitude of anode current, mA 375 



Characteristics of the rectified voltage dependence of the  rectified current

  Characteristic Curves rectified voltage (y-axis) from the rectified current (x-axis) when the resistance of each arm of the secondary winding of the transformer 30 Ohm and a filter with a capacitive input.