01-03-2022 Post does not mapped to Knowledge Tree deemon Posts 24 Joined on 05-25-2004 Post #: 26 Post ID: 26661 Reply to: 26656 Tube current measurement Hi Domidaw !  The first thing that we need to find out - is a REAL tube plate current at the moment when the R22 resistor starts smoking . I mean not a calculations that might be based on some faulty conclusions but a real current that an ammeter does show . What you need to do is to disconnect wires at the D testpoint ( tube plate ) and connect any reliable ammeter between them ( maybe a multimeter in "ampere" mode ) , turn the amplifier on and then tell us what current multimeter shows . All further actions will depend on a result of this measurement , of course ....

01-03-2022 Post does not mapped to Knowledge Tree Romy the Cat Boston, MA Posts 10,156 Joined on 05-28-2004 Post #: 27 Post ID: 26662 Reply to: 26661 Thanksm Dima Domidaw, I am not participating in helping you too much because I have my own diabolical fun observing your suffering. Sorry, my friend, I was in the same shoes so many times, literally having the same feeling and speaking with the same language, that observing you I feel like I am reading my own diary . Deemon above is Dima, the gentleman without whom the Milq would never materialize. You are in very good hands. You know, my valve who gave to people chemotherapy say to them that it doesn't work if it would not hurt 😊 "I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

01-04-2022 Post does not mapped to Knowledge Tree Domidaw Posts 15 Joined on 08-09-2021 Post #: 28 Post ID: 26663 Reply to: 26662 Data and photo with a view of the battlefield Hello Dima !!!! At point D I have 0.920 mA ... at 198v on pin 4. 238v before resistor R22 and 200v after resistor R22. On pin 5 I have -82. There is 82mV across the R21 resistor. I noticed that when I turn the VR2 potentiometer, thus increasing the reading along the R21 resistor, the voltage behind the R22 resistor decreases, the voltage in front of it, i.e. 238v, does not change. Ps. Romy, I think you might have mistaken my thanks to you. I thank you for contacting Dima regarding my case. There was nothing sarcastic about it. It's all just love. You know how I am suffering now, because there is no better word than suffering to describe the situation I am in now, so you also realize how much help of all of you mean to me.

01-04-2022 Post does not mapped to Knowledge Tree Domidaw Posts 15 Joined on 08-09-2021 Post #: 29 Post ID: 26664 Reply to: 26663 My "Bro science" 5hours pass when I sit in the chair and stare at work of my life (amplifier), like some haunted man. As you can see, I divided the amplifier into two parts, the power supply is  in a separate housing. I did it because the chokes and the OTP transformer were delivered to me, in large cans flooded with resin. I just couldn't find an idea how to put it all into one, not too large housing. So I decided to do the same as Romy did with his big 6-channel amplifier, that is, to divide it into two parts the power part and the amplifier part. As a result, I gain a small space occupied by the entire amplifier. But now I wonder if this is not  the cause of my problems. I checked all connections again and I am not able to find the error, so I think that either one of the components is damaged or I made some technical error that is the results from my ignorance in the field of electronics. I am reading such an article now: https://phys.libretexts.org/Bookshelves/University_Physics/Book%3A_Introductory_Physics_-_Building_Models_to_Describe_Our_World_(Martin_Neary_Rinaldo_and_Woodman)/22%3A_Source_of_Magnetic_Field/22.02%3A_Force_between_two_current-carrying_wires  and I wonder if my problem is not some interference betwen wires in the cable that connects Ps with  a amplifier part.

01-04-2022 Post does not mapped to Knowledge Tree JJ Triode Posts 99 Joined on 09-12-2007 Post #: 30 Post ID: 26667 Reply to: 26663 Three different currents that should all be the same Hi again Domidaw. Your latest results look inconsistent: a 38V drop across 50-ohm R22 would imply 0.76A or 760 mA flowing through R22. If C10 is not leaking any significant DC current then this 760 mA should be the current through R21 and point D. But you have 82 mV across the 1-ohm R21, implying 82 mA of current. Then at D you say it is only 0.920 mA! Something is wrong; perhaps the resistances are not what you think? Also, to measure a current you have to open the circuit at the desired point and make all the current flow into one lead of the meter and out the other; it is not like measuring the voltage to ground. How did you measure the current at D?

01-04-2022 Post does not mapped to Knowledge Tree Domidaw Posts 15 Joined on 08-09-2021 Post #: 31 Post ID: 26668 Reply to: 26667 The current at point D I made this measurement in such a way that I unsoldered the wire from pin 4 (black in the photo) and connected to it the red clip from the multimeter, and to pin 4 I connected the black clip from the multimeter. I set the multimeter to the mA reading position. Is it possible that I somehow burned the output transformer and this is the problem ? I have to try the other one.

01-04-2022 Post does not mapped to Knowledge Tree Domidaw Posts 15 Joined on 08-09-2021 Post #: 32 Post ID: 26669 Reply to: 26668 New multimeter I ordered new  wires and ordered a new multimeter. Maybe mine is faulty. This is Chinese, not very expensive equipment. I will replace all the wires in amplifier  and measure everything again with a new multimeter. Fu.ck....

01-10-2022 Post does not mapped to Knowledge Tree Domidaw Posts 15 Joined on 08-09-2021 Post #: 33 Post ID: 26670 Reply to: 26669 News from the war zone I replaced all the wires, replaced the capacitor C11, C10, returned to the 12w resistor R22, also replaced the L2 choke. Now I sit for over two hours next to amplifier, just like sitting at the bedside of a sick loved one person.  Nothing is burning and it does not heat up much. I put a thermometer from a multimeter on the resistors that were the warmest. After two hours of continuous operation, the R22 resistor has a temperature of 55 degrees Celsius, and the resistor R2 is 72 degrees Celsius. The voltage across R21 drifts between 179mV and 181mV. Please look at the diagram, the red numbers are the actual measurements ..... I am mentally and physically exhausted (my back hurts enormously) when I waited for a new multimeter and cables, at that time I assembled the preamplifier (diagram below). It was on PCBs so it was easy, but it still took some concentration and some work. So I didn't leave this crazy mental  state for even a day. I look forward to your evaluation of my new measurements ...

01-10-2022 Post does not mapped to Knowledge Tree JJ Triode Posts 99 Joined on 09-12-2007 Post #: 34 Post ID: 26671 Reply to: 26670 Ready to connect a speaker! Hi Domidaw, it looks like your amplifier is working pretty much correctly. The plate current in the output tube is a little below the recommended range (180 mA versus 200-280 mA in Romy's diagram) but too low is better than too high and you can adjust it by changing VR2 (monitor voltage at R21 to get into the desired range.) I have no idea what was wrong before. I can't say anything about your preamp as I am not familiar with the design. The only strange thing is that I don't see a volume control anywhere, but maybe I missed something.  Anyway now that you have one working channel, you can connect a speaker to the amplifier, feed in some music and check that you have something recognizable coming out.  By the way if you don't have a speaker connected then you should have a "dummy load" (a power resistor of about 8R) across the output terminal of the amplifier.

01-10-2022 Post does not mapped to Knowledge Tree Domidaw Posts 15 Joined on 08-09-2021 Post #: 35 Post ID: 26672 Reply to: 26671 Thank you JJ. I connected the loudspeaker to check if the music was flowing from it. The amplifier works !!! I hear the music!!! I'm exhausted. Now it's evening at my place, I can hear the rain outside. I think I'm going to do what I wanted to do countless times while building this amplifier ... I'll will just turn off the lights, go to the corner of the room, sit on the floor there, curl up into a ball and cry loud and hysterical. Or no..., I will just choke this hysterical loud cry until it is barely audible and I will cry like that. Like  a real man is crying.