EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: RobNorthen on May 31, 2020, 08:10:41 am
-
I'am waiting for an Elektronika 7K clock to arrive. It is the big brother of the Elektronika 7M. The smaller 7M got a dimmer switch, but the large 7K does not. I would like to add one. The logic boards seems very much alike. I have attached the schematics for both.
Have tried reading the 7M schematic to see how the dimming is done, but have big troubles undertand and follow it (Russian). I think switch "SA4" is the dimming that runs to "xs1" cable loom, goes to to pin 10 on IC "D4". It also seems like the other side of the switch goes to a transformer tap.
It just seems very strange to switch AC voltage into an IC, so I'am pretty sure I missed something.
Was also thinking about just adding a big power resistor in series with the filaments power, but not sure its the right way to go. I would guess the 7M clock is messing with grid or segment voltage, to dim the display.
Would be happy if someone could help.
https://www.glaver.org/blog/e7-06-schem-web.pdf (https://www.glaver.org/blog/e7-06-schem-web.pdf) - Elekronika 7K
https://www.glaver.org/blog/elektronika-schematic.pdf (https://www.glaver.org/blog/elektronika-schematic.pdf) - Elektronika 7M
-
I think switch "SA4" is the dimming that runs to "xs1" cable loom, goes to to pin 10 on IC "D4". It also seems like the other side of the switch goes to a transformer tap.
It just seems very strange to switch AC voltage into an IC, so I'am pretty sure I missed something.
Not really. SA4 connect negative pole of VD1 rectifier with common wire of the filament circuit.
Was also thinking about just adding a big power resistor in series with the filaments power, but not sure its the right way to go. I would guess the 7M clock is messing with grid or segment voltage, to dim the display.
As I understand it, there is a tricky method of the anode voltage control: instead of directly changing the anode voltage, a negative bias is added at the cathode side.
P.S. As for 7-06K, the simplest method here is to add PWM-controller to the "+25V" (anode voltage) circuit.
-
Thank you Canis, it makes good sense with the +25v, I will do that. :-+
-
The point of this is, of course to dimm the light, but I was also hoping this would give the tubes a longer life ?
I will be replacing all the tubes with NOS ones.