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Old 24th January 2008, 09:01 PM   #1
SHiFTY is offline SHiFTY  New Zealand
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Default PSUD question

Using a GZ34/5AR4, with a 500V/120ohm PT, CLC of first cap of 40uF, a 1.2H/18ohm choke, then a 560uF cap with a load of 100mA, I get crazy graphs and an over-current error.

Is the choke too low in resistance/inductance and that is overstressing the GZ34? It's an old monster of thing, would I be better buying a 5H ~100 ohm one?

Thx
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Old 24th January 2008, 10:29 PM   #2
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Things look all right to me. That is, without judging the quality of your supply, PSUD seems to handle it fine. Screen shot below.

http://www.just4sheep.com/site/images/PSUD.pdf
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Old 24th January 2008, 11:52 PM   #3
SHiFTY is offline SHiFTY  New Zealand
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Hi

Sorry made a mistake in my original post the power transformer is 850VCT, or 425-0-425

I get it, you have to highlight the graph and drag it to rescale.

Hmmm, looks like I'm getting 400mA pulses through the GZ34, my choke must need more inductance/resistance...

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Old 25th January 2008, 12:48 AM   #4
Jeb-D. is offline Jeb-D.  United States
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Didn't get a chance to run the sim, but by looking at your values it seems like a tough load for the rectifier durring the power up cycle(if the rectifier you are refering to does cross-reference the 5AR4). Especially in a worst case, real-world situation, like tubes are warmed up then you power it off, then back on before they are cooled down.

I'd either,
- Reduce capacitance
- Increase L and or R (you could just add a resistor in series with the choke if you already own the choke and have the voltage headroom to do so)
- Change rectifier type

Or a combination.
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Old 25th January 2008, 02:19 AM   #5
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Quote:
I get crazy graphs and an over-current error.
The over-current error is probably caused by using a constant current load instead of the equivalent resistor load. The sim assumes that the load will draw the specified current from the start, which of course it won't.
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Old 25th January 2008, 02:37 AM   #6
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Make sure you set the right resistance readings for your transformer. That threw me off for a long time.
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Old 9th March 2008, 12:11 AM   #7
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I've had similar problems with 'constant current draw'....which of course a plate wont do. Set the stepped load option to say, after ~1s just to keep the simulator happy that it's let the voltages get up a little before drawing the load

L
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