Low-distortion Audio-range Oscillator - Page 44 - diyAudio
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Old 21st September 2012, 09:14 PM   #431
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Quote:
Originally Posted by dennismiller55 View Post
I have found on difficult solder that I get good results if I pre-wet my wick with flux. Even if the wick already has flux in it (the flux dries out).
OK. I don't have any flux so I suffered through a painful removal of some parts off of his board. What a mess! I guess I'd better go buy some. I was using Chem-wick, but it may be old.
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Old 21st September 2012, 11:07 PM   #432
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I put Victor's oscillator into Tina just in case I need to make one myself. I'm not sure it's oscillating. I looked up the parts he's using and used something else that's similar, like a high gain PNP transistor BC560C, and the J111 jfet. I don't really understand this circuit, so I am unable to fine tune it. Any help is appreciated.
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Old 22nd September 2012, 12:07 AM   #433
davada is offline davada  Canada
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Quote:
Originally Posted by dirkwright View Post
I put Victor's oscillator into Tina just in case I need to make one myself. I'm not sure it's oscillating. I looked up the parts he's using and used something else that's similar, like a high gain PNP transistor BC560C, and the J111 jfet. I don't really understand this circuit, so I am unable to fine tune it. Any help is appreciated.
If you know how to install parts into LTspice I can send you Jfet models.
I don't use Tina so I can comment on that.

Your loop gain is too low.

David.
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Old 22nd September 2012, 12:21 AM   #434
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Originally Posted by davada View Post
If you know how to install parts into LTspice I can send you Jfet models.
I don't use Tina so I can comment on that.

Your loop gain is too low.

David.
Hmmm, thanks. I did notice that I had the power supply set to +/-5V, so I changed that. The J111 jfet is supposed to be the same as the one Victor used. I also copied all of his resistor and capacitor values. How do I increase the loop gain?
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Old 22nd September 2012, 12:29 AM   #435
vicnic is offline vicnic  Latvia
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Quote:
Originally Posted by dirkwright View Post
I put Victor's oscillator into Tina just in case I need to make one myself. I'm not sure it's oscillating. I looked up the parts he's using and used something else that's similar, like a high gain PNP transistor BC560C, and the J111 jfet. I don't really understand this circuit, so I am unable to fine tune it. Any help is appreciated.
Dirk,
1) I see two mistakes in schematic:
R17 must be 120k.
R10 must be 10k + 100ohm.
2) Settling time after swich on is tens of seconds. Simulator must be configured for this, if it possible.
3) Power supply voltage must be +/-15V. With lower voltage, you may not drive JFET properly.
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Old 22nd September 2012, 12:36 AM   #436
davada is offline davada  Canada
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Originally Posted by dirkwright View Post
Hmmm, thanks. I did notice that I had the power supply set to +/-5V, so I changed that. The J111 jfet is supposed to be the same as the one Victor used. I also copied all of his resistor and capacitor values. How do I increase the loop gain?
The RDs on matches and that about it.
The Idss is much higher and the capacitance is lower for the 4391.
I'm not sure the the gate is ceter on the j111 as it is with the 4391.

I have the model if you want it.

You can try decreasing R7's value. It's tight for gain adjustment with this oscillator.
Any attempt to increase gain at the output drive will upset the filter.

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Old 22nd September 2012, 01:50 PM   #437
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Quote:
Originally Posted by vicnic View Post
Dirk,
1) I see two mistakes in schematic:
R17 must be 120k.
R10 must be 10k + 100ohm.
2) Settling time after swich on is tens of seconds. Simulator must be configured for this, if it possible.
3) Power supply voltage must be +/-15V. With lower voltage, you may not drive JFET properly.
Thanks!

I have trouble using my software to look at this circuit. I tried the software 'scope but didn't see any output. Since it doesn't have a signal source, I'm at a loss right now to figure out if it's working correctly.
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Old 22nd September 2012, 02:06 PM   #438
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Originally Posted by davada View Post
The RDs on matches and that about it.
The Idss is much higher and the capacitance is lower for the 4391.
I'm not sure the the gate is ceter on the j111 as it is with the 4391.

I have the model if you want it.

You can try decreasing R7's value. It's tight for gain adjustment with this oscillator.
Any attempt to increase gain at the output drive will upset the filter.

David.
Thanks for your help.

I'm getting basically no voltage across the jfet. I can't figure out why. There's a tiny negative DC voltage from drain to source, and the gate is at 170mV or thereabouts.

I just need the *.lib file for the jfet, thanks.
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Old 22nd September 2012, 04:49 PM   #439
EssB is offline EssB  United Kingdom
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You'll have to run a transient analysis for a long time.
When simulating oscillators, I use a current source to inject a few cycles right at start up. this can get it running a lot quicker.
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Old 22nd September 2012, 05:16 PM   #440
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Originally Posted by EssB View Post
You'll have to run a transient analysis for a long time.
When simulating oscillators, I use a current source to inject a few cycles right at start up. this can get it running a lot quicker.
Ah! so that's what I do.

Ok, tried that. I got a really ugly looking oscillation. I ran it for both 10 and 20 seconds. Sump'in ain't right.
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