Thanks. My main experience with transformers is very small ones in boost converters, where ringing on the input at high load can easily exceed the saturation current (if you aren't careful). Then magic smoke happens. Not something I want to see with mains voltage!
I'm finding out that using a CLC filter is probably the cause of the high currents I am seeing in my simulations, so I need to run some figures to come up with reasonable component values for an LC filter. I found these two articles that explain it in terms I can (almost) understand: Choke or Capacitor Input? and http://www.tubebooks.org/books/schure_rectifiers.pdf
Transformers take *minutes* to heat-up and burn-up.
A large (25KVA) transformer can be loaded to 200% of rated current for an hour, as when several houses all electric-cook holiday dinner at the same time.
0.001 second cap-peaks do not matter.
The RMS value is what might cook your transformer. Looks like a half-Watt of heat in the transformer. Odds are your tranny won't get more than warm.
Generally if your AC Amps rating is at least twice your DC Amps demand, you have nothing to worry about. You can cut this a little closer (1.8X, 1.6X) but typically ripple-sag becomes a problem before smoke happens.
SPICE/Probe is showing "negative" current because that's how it thinks. Put the probe on the other end of the resistor, it will show positive. Or edit the trace value to "-(I(R1))" so it agrees with how people think.
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Before I start blowing things up, I have a question about this. From what I understand, the heater has to be within 100V of the cathode. The cathode for the pentode section of the ECL85 is at the output voltage (say 180V). The heater is biased to the maintenance voltage/zener voltage. If I used a 60V zener, that would put the voltage difference between the heater and the pentode cathode at 120V, which exceeds the spec. I guess one solution would be to bias the heater voltage higher, so can the heater be +ve wrt the triode cathode?
The data sheet for the 6GV8 give both a +ve and -ve wrt cathode. The +ve value is 100V, the -ve value is 200V. Does that mean that the heater can be 200V below the cathode? Is this the same for the ECL85?
Also, the datasheet says that the max plate voltage is 250V, typical is 50V-65V for triode and 100Vfor pentode (the typical numbers are higher for the 6GV8). Are the figure given for the anode voltage relative to the cathode?
Supply is up and running and providing a steady 179V, which is basically perfect , and has everything running within their operating parameters. I would just like to know exactly what the limits are so I can provide a bit of variability in the components used (such as different VR tubes and 'equivalent' pentode/triode tubes) and allow an adjustable output voltage while still staying within those operating parameters (hence all my questions).
I had an interesting moment testing it, when I connected what I thought was a 4.4K load across the output (with two 2.2K 10W resistors in series). I couldn't understand why the output voltage dropped to around 1V. Turns out the resistors were actual 2.2 Ohms. The ECL85 was glowing nicely. I'm surprised I didn't see smoke.
I want to thank you guys for taking the time to help out a newb like me. It is very much appreciated.
I had an interesting moment testing it, when I connected what I thought was a 4.4K load across the output (with two 2.2K 10W resistors in series). I couldn't understand why the output voltage dropped to around 1V. Turns out the resistors were actual 2.2 Ohms. The ECL85 was glowing nicely. I'm surprised I didn't see smoke.
I want to thank you guys for taking the time to help out a newb like me. It is very much appreciated.
If you need spare tubes, here are budget alternatives to ECL85.
4x 6F5P = 6GV8, ECL85 Triode Pentode Vacuum Tube Russian Soviet NEW in BOX 1987 | eBay
Yes. I might get through a few before I'm done!
Yes, but the section about standard operating conditions says nothing about positive or negative bias, whereas the 6GV8 datasheet is explicit:
"Heater positive with respect to cathode: 100V. Heater negative with respect to cathode: 200V"
So I am wondering if the 6GV8 is more tolerant in this regard, whether it is an oversight in the ECL85 datasheet, or whether it is just not something that was ever tested with the ECL85.
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