Hi Martin
I shall have a play when I get a chance. Increasing the anode voltage is
not a problem and a pot in cathode is easy to try. Do you know if any
other voltages or component values were changed? There is too much magic
involved with these tubes so I stuck closely to the datasheet and the
arrangements described by JB Dance.
Grahame
On 17/02/2019 11:41, Dekatron42 wrote:
Telefunken and other manufacturers of counters with the E1T used two
simple changes to the design to be able to adjust the circuit to be
able to use tubes with wider tolerances, the first was to run them in
a design with up to 400V anode voltage, the design was compensated for
this higher voltage, but they also had a much simpler design which
just incorporated a 10k potentiometer in series with the 15k cathode
resistor. This potentiometer is then used to adjust for different tube
characteristics. I haven't seen Philips present similar circuits but
they were probably using them too. I've tested both designs but find
the one with the 10k potentiometer a lot easier to use. It let me run
quite a few more of the tubes in my scrap bin, but more importantly I
think it is a good way of sorting tubes that behave like new from
tubes that will soon end in the scrap bin, apart from letting them run
in an unmodified original circuit. I haven't found any documents
describing this change but it appears in some of the Telefunken counters.
/Martin
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