[sdiy] Help with thyratron metronome - NOT A JOKE !!

[René Schmitz]

Hi again,

The values for R1 and R2 seem to be a bit low, I would have 
expected somewhat higher values, to keep the dissipation low.
However, I think I now understand what the NE1 and 
R6/R7/C2 are for. When the neon fires it also charges C2 quickly, 
which prevents that the neon discharges the cap C1, so it just 
makes a short flash, goes out of conduction, and can't rob current 
from C1 until R7 discharged C2. A quick test of my theory from 
yesterday, would be to disconnect NE1 from the rest of the circuit, 
and see if it still oscillates. 

If I were playing with that circuit, the first thing would be to 
use an insulating power transformer to avoid any risks with the 
mains voltage! Yet, be careful!

I think a relay could be used to make the circuit gateable, you could 
use a 1PDT. The normally off contact is in series with the 1Meg resistor, 
the grid is at the common terminal, and another 1Meg resistor goes 
to "GND" on the normally on contact.

I have an aside here for the other tube enthusiasts: 
The circuit is actually similar to a thyratron VCO I have built. 
Instead of discharging the cap C1 thru a resistor its discharged 
thru a current sink, and you have a CCO core. If anyone wants to 
see a circuit enquire privately.

Cheers,
 René


At 03:34 23.02.02 -0800, you wrote:
>Ok, here are the values for the resistors
>
>R1 4.7k
>R2 4k
>R3 1m
>R4 330k
>R5 1m
>R6 6.8k
>R7 1m
>C1 .47mf
>C2 .47mf
>                                        NE1
>                2D21                    ||
>                ,-----------------------||--
>110             . .  |     |      |        |
>---------------|. . [      |      |        \
>      |         . .        |      |        / R6
>      /           |        C||    /        \
>      \ R1        |        C||    \R5      |----
>      /           |     L1 C||    /<-      |    |
>      |           |        C||    \  |     \    |
>      |           |        |         |     /  -----
>      /  R2       |        |         \     \  -----C2
>      \           |        |         /     /R7  |
>      /<- / \ / \--      -----     R4\     |    |
>      \     R3           ----- C1    /     |    |
>      |                    |         |     |    |
>110   |                    |         |     |    |
>-------------------------------------------------
>
>
>
>
>
>
>
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uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159