PSUD question

SHiFTY · 24th January 2008, 08:01 PM

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

zigzagflux · 24th January 2008, 09:29 PM

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

SHiFTY · 24th January 2008, 10:52 PM

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...

Jeb-D. · 24th January 2008, 11:48 PM

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.

ray_moth · 25th January 2008, 01:19 AM

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.

astouffer · 25th January 2008, 01:37 AM

Make sure you set the right resistance readings for your transformer. That threw me off for a long time.

Psychobiker · 8th March 2008, 11:11 PM

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

24th January 2008, 08:01 PM	#1
SHiFTY diyAudio Member Join Date: Jul 2002 Location: New Zealand	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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24th January 2008, 09:29 PM	#2
zigzagflux diyAudio Member Join Date: Oct 2006	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

24th January 2008, 10:52 PM	#3
SHiFTY diyAudio Member Join Date: Jul 2002 Location: New Zealand	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...

24th January 2008, 11:48 PM	#4
Jeb-D. diyAudio Member Join Date: Nov 2005 Location: SoCal	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.

25th January 2008, 01:37 AM	#6
astouffer diyAudio Member Join Date: Jun 2004 Location: Pittsburgh, crumbling wasteland	Make sure you set the right resistance readings for your transformer. That threw me off for a long time.

8th March 2008, 11:11 PM	#7
Psychobiker diyAudio Member Join Date: Jul 2005 Location: Montréal QC	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