I got them from eBay
https://www.ebay.ca/str/semitronus
I have other TO226 transistors from another project. I'll check the compatibility tomorrow. If not compatible I'll try with 2N5401 and 5551...
https://www.ebay.ca/str/semitronus
I have other TO226 transistors from another project. I'll check the compatibility tomorrow. If not compatible I'll try with 2N5401 and 5551...
Oh, I see. That's one reputable place for getting things not what they say they are, as far as I heard.....not saying those that you got are bad though....
Most of semiconductors on Ebay are fake, don't use them.
Especially these that are 'discontinued' or 'obsolete'.
Actually even capacitors are fake too, I guess the only 'safe' components are resistors and metal connectors
Hm..... even more amazing: Bulgaria is country on the other side of the world, but If I order 106 of each, it cost me 108.76 ''BGN''(82 ''CAD'' or 59 ''USD'') with taxes and shipping (0 ''BGN'', ''CAD'', ''USD''). On top of that - Incoterms: DDP (Duty and customs fees paid by Mouser)?? Not that I'm complaining..... I am just wondering, bad algebra?
. I am just wondering, bad algebra?
Interesting!
I putted back the 620 Ohms resistor R6 and both R501, R601 in circuit.
I injected 1 Vrms at the input with +/-28 VDC at the rails. Distortion is flat and symmetrical.
Then I raised the rails to +/-29 VDC. just 1 volt more on each. And look at that!
Thanks but, I am just following everyone proposals here ;-) I admit I learn a lot from those. Thanks to all contributors.
My goal is to have one 100% functional and from there, I will redo the PCB with all the revisions. I already have bought the Dissipante 3U chassis and I want to bring this project to the end
This time we got it!
I received my transistors and replaced them.
I have my rails at +/-32VDC, the voltage DC at output = -415mV (DVM), the voltage AC at the input is 3.0106 Vpp at 1 kHz (Trace 1), and I have a clean sinus wave at the output at 55.694 Vpp (Trace 4).
DC voltage across R503 is stable at 1.04 VDC. There are no part that show heat on my fingers.
My FFT show the fundamental peak at 976.56 Hz at +25.53 dBV with the third harmonic at -26.48 dBV, that's (+25.53 - (-26.48)) = 52.01 dBV below the fundamental.
If push the input to create more distortion, the flat are very symetrical.
And, for the pleasure to share... My second scope DHO914S start to behave like the first one with the Bode Plot problem on channel 3 and 4. I called the Sale Manager at Electro-Meters. He upgraded me to a MSO5074 with the AWG option required in order to be able to do the Bode Plot, with no charge! That..., that is what I call a pretty good and generous after sale warranty!
Here...
I received my transistors and replaced them.
I have my rails at +/-32VDC, the voltage DC at output = -415mV (DVM), the voltage AC at the input is 3.0106 Vpp at 1 kHz (Trace 1), and I have a clean sinus wave at the output at 55.694 Vpp (Trace 4).
DC voltage across R503 is stable at 1.04 VDC. There are no part that show heat on my fingers.
My FFT show the fundamental peak at 976.56 Hz at +25.53 dBV with the third harmonic at -26.48 dBV, that's (+25.53 - (-26.48)) = 52.01 dBV below the fundamental.
If push the input to create more distortion, the flat are very symetrical.
And, for the pleasure to share... My second scope DHO914S start to behave like the first one with the Bode Plot problem on channel 3 and 4. I called the Sale Manager at Electro-Meters. He upgraded me to a MSO5074 with the AWG option required in order to be able to do the Bode Plot, with no charge! That..., that is what I call a pretty good and generous after sale warranty!
Here...
With the goods results above, I soldered back the two resistors R301 and R401 and the C3 capacitor. Then I raise the frequency and could reach 4.5 MHz without oscillation. I just had to lower the input voltage to preserve the 1.04 VDC across R503.
After that I installed the AWG License that I just received and did a Bode Plot from 10 Hz to 500 kHz to see the Phase Margin. It is really good in my point of view. The PM(0dB) value is the frequency and the phase where the gain fall down to 0 dB, the safe point before oscillation. At that frequency of 398.1 kHz, the phase shift is -89.52 degrees! From what I read in the book, we must make sure that we never reach 180 degrees before unity gain. I think we have achieve that ;-)
After that I installed the AWG License that I just received and did a Bode Plot from 10 Hz to 500 kHz to see the Phase Margin. It is really good in my point of view. The PM(0dB) value is the frequency and the phase where the gain fall down to 0 dB, the safe point before oscillation. At that frequency of 398.1 kHz, the phase shift is -89.52 degrees! From what I read in the book, we must make sure that we never reach 180 degrees before unity gain. I think we have achieve that ;-)
This morning I soldered back two output MOSFETs to make further tests. Everything was looking good for the voltage at 1 kHz. When I started to raise the frequency, I noticed an oscillation at the output around 22 kHz. On my new scope, I can zoom in with a rectangle on the touch screen.
From that point I could get ride of it by calibrating the BIAS. Then step by step in a loop I was raising the frequency until the oscillation came back, readjusting the BIAS, to the point where I had no oscillation at 31 kHz but could see the beginning of an oscillation at 32 kHz. And I wasn't able to adjust more the BIAS to get ride of it. Rails are at +/-32 VDC. Output at 38.62 Vpp.
The oscillation frequency is 5.714 MHz and the DeltaY 3.583 Vpp for a 43.032 Vpp output.
Any idea what would be the source of this oscillation?
From that point I could get ride of it by calibrating the BIAS. Then step by step in a loop I was raising the frequency until the oscillation came back, readjusting the BIAS, to the point where I had no oscillation at 31 kHz but could see the beginning of an oscillation at 32 kHz. And I wasn't able to adjust more the BIAS to get ride of it. Rails are at +/-32 VDC. Output at 38.62 Vpp.
The oscillation frequency is 5.714 MHz and the DeltaY 3.583 Vpp for a 43.032 Vpp output.
Any idea what would be the source of this oscillation?
Maybe this:
https://www.diyaudio.com/community/threads/unusual-amp-from-1987.357369/post-6513768
I can't read from your schematics (too small) what gate stoppers you are using...
https://www.diyaudio.com/community/threads/unusual-amp-from-1987.357369/post-6513768
I can't read from your schematics (too small) what gate stoppers you are using...
I am using Exicon ECX10P20 and ECX10N20.
I tried replacing the 470 Ohms of the ECX10P20 with 220 Ohms. It was worse. I replaced the new 220 Ohms with 680 Ohms and it may be a bit better, but nothing really impressive.
I don't know what you mean by double die or single die. The Cis of the daasheet says 500pF for both.
But I may have found my problem. Because I made a mistake on my PCB, by inverting the Drain and the Source of the ECX10P20, I must cross two little wires to revert my mistake. Like this:
So I tried to separate them bit like this:
And since this change, I can now go as far as 52 kHz before the oscillation came in, compared to 33 kHz in the preceding picture. These wires must create a capacitor between the pins...
I tried replacing the 470 Ohms of the ECX10P20 with 220 Ohms. It was worse. I replaced the new 220 Ohms with 680 Ohms and it may be a bit better, but nothing really impressive.
I don't know what you mean by double die or single die. The Cis of the daasheet says 500pF for both.
But I may have found my problem. Because I made a mistake on my PCB, by inverting the Drain and the Source of the ECX10P20, I must cross two little wires to revert my mistake. Like this:
So I tried to separate them bit like this:
And since this change, I can now go as far as 52 kHz before the oscillation came in, compared to 33 kHz in the preceding picture. These wires must create a capacitor between the pins...