My head hurts just thinking about that.
This AM's read is 1.54V.
My head hurts just thinking about that.
The fact that it is holding voltage over days, sounds more like a battery than capacitor, but surely non-linear discharge characteristic so ignore my ohms law musings.mediatechnology wrote: ↑Thu Apr 05, 2018 6:55 amMy head hurts just thinking about that.
This AM's read is 1.54V.
The "battery" comment was a joke in light of Wayne's battery faucets.
Joke? What's that? It went straight over my head.The "battery" comment was a joke in light of Wayne's battery faucets.
Maybe because it was a personal joke with Wayne, about his plumbing.. see viewtopic.php?f=11&t=406&start=380#p11028KMN wrote: ↑Thu Apr 05, 2018 2:24 pm Trying to get the models perfect in the simulations is a big topic of discussion where I work, ie power conversion, not audio. Though even the grizzled old engineers, aware of the effect, haven't made much of a fuss about it. When I've noticed the effect in the lab, hv dc power supply filter caps, the output impedance is so high I haven't been able to get the "battery" to do any appreciable work. It did definitely left me wondering though. I have trouble imagining it being very significant, if even audible, in real world apps unless the DC is a problem, as mentioned earlier, when the cap gets switched into play.
In my searches it seemed as if most are using simple linear model to characterize it which hasn't seemed very satisfying. Then I found this paper, and see now that more complex models have indeed been proposed: https://cdr.lib.unc.edu/indexableconten ... 62c379949c It was new info for me that I found interesting.
This is a great thread which piqued my curiosity enough and caused me to do some google searching.
Joke? What's that? It went straight over my head.The "battery" comment was a joke in light of Wayne's battery faucets.
In the 90s, my hamfest tool kit contained a 9V battery and a simple DMM to characterize unknown film caps found in the wild. The basic procedure was to charge the unknown cap for five counts, short it for one count, and then measure the recovery voltage. After some training with known samples, the measured recovery voltage could reliably identify the dielectric of a film cap, adding another data point as to whether I needed to buy the caps or skip them.KMN wrote: ↑Thu Apr 05, 2018 2:24 pm In my searches it seemed as if most are using simple linear model to characterize it which hasn't seemed very satisfying. Then I found this paper, and see now that more complex models have indeed been proposed: https://cdr.lib.unc.edu/indexableconten ... 62c379949c It was new info for me that I found interesting.
montemcguire wrote: ↑Thu Apr 05, 2018 8:38 pm In the 90s, my hamfest tool kit contained a 9V battery and a simple DMM to characterize unknown film caps found in the wild. The basic procedure was to charge the unknown cap for five counts, short it for one count, and then measure the recovery voltage. After some training with known samples, the measured recovery voltage could reliably identify the dielectric of a film cap, adding another data point as to whether I needed to buy the caps or skip them.
Is the Mallory cell in series with the cathode or in series with the grid? I saw in the application circuit it in series with the grid but IIRC you mentioned it connected to the cathode.There was a type of grid bias battery used in the 1930's that looks a lot like a hearing aid battery, clipped in near the tube cathode. I found one awhile back, and it still has a charge.