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Issue 3 PCB
More fluctuating readings !! Only a year late so far. Out with the dremel, unrectified HT is leaking in to my HT regulator and causing hum modulation on the anode voltage. At the outset I thought it would be a simple project, I mean "Valve testers" are pretty crude, aren't they?
Oh ripple, Oh noise, synchronise AC test generator with meter reading module, for a more stable reading.
Still disastrously unstable. Out go all zenners, and in with precision voltage reference for HT and grid...
Starting to look a bit more like it, but not at all stable, ditched AC heaters, for regulated DC. That transconductance is so sensitive to heater voltage fluctuations that with the digital meter I end up measuring the electric cooker turning on and off! grrr.
Variable grid and anode voltage.
With a variable cathode current and measure the grid voltage. AC heaters.
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last updated Mon Jun 30 22:31:36 BST 2008