micon21

Sorry, but how does the signal get to pin8. I see that the cathode feeds transistor Q8, no signal comes to Base Q8 through R11.

Alas, I got a good result only after some changes in the board. I found that R32, R33 are detrimental to the signal, I do not understand why they are needed. I increased R43, R44 to 300k, R7, R8 to 470 oms got undistorted sine waves with a large range - 140v. I plugged the headphones, for normal listening it is enough for me on the output and 70v. It is also not clear what improves the section Servo, on one board I did not set the elements for Servo. I looked both on and off, but did not see the essence. Translated with www.DeepL.com/Translator (free version)

I understand and see that the first tube works only as a preamplifier, especially I see a small gain on the 3pin output.

? Maybe I'm wrong, but I understood it this way: the signal goes only to the first lamp 2pin. output from 3pin. through the second lamp 6922 signal does not pass, it has a different purpose, and you can use cheaper brands. EL34 also does not receive a signal, the signal goes through R43, 44

I checked everything yesterday, all resistors, transistors, no fault found, I put a different bulb, it didn't help, and was very upset. i planned to throw the board away and be done with it. but i accidentally discovered that increasing 100k leads to an increase in signal. The result is much more interesting than it was. the sinusoid is beautiful, not crooked. in the evening I will plug in my headphones and listen to how it plays....

Thank you for trying to help me. I got a good undistorted sinusoid, with a large sweep of more than 110v at the output, with an input signal of 1.2v. after adjusting the resistors R43, R44, R7, R8. In the end I replaced 100k with 270k and 100 ohms with 2k. now also on the third leg of the first lamp, I see a nice not crooked sine wave. This change did not change the voltages on all legs of both 6922 lamps.

I understand that it is very important that all resistors match the ratings. I strictly adhered to the specified values. I used one 197 and one 356, as JoaMat recommended

Tester measurements are as follows: lamp one, 1 pin - 74v. 3pin - 2v The second top lamp: 6pin-200v. 7pin- 61v el34, 8 pin - minus 365v

on the first leg of the first lamp, photo 1. on the third leg of photo 2

filed 220, 400, 460, but alas, the result is not happy. !!! fed the input BALANCED signal 0.35v, photo 1. the output received a swing of 82v and 84v, but in terrible condition, photo 2 P.S. I get an undistorted signal with a swing of 20v at the output if I input 0.170v It's not enough for headphones.

life is short, but music is eternal....

you won't believe it, many missiles from russia were shot down over my city in the morning, and I was sitting there trying to figure out why the board wasn't working properly. it was more interesting to me....

The circuit I showed as an example. for mini Т2 voltages are different. I made three of these, of course first adjusted the necessary voltages. I have an oscilloscope, it will tell me if the board is working or not. there is a jumper on the board, SERVO ENABLE, should it be shorted the first time it is turned on? if it is not connected, what happens?

THANK YOU for having someone willing to help me. I have a lot of experience in electronics. i got my first static headphones in 2015 KOSS 950, used, I made a transistor version. I did not like the sound of 950, I bought a Perun, then bought used SR-007 and soldered a tube amplifier. I currently have 009S. used. I can not buy amplifiers for 2000...3000$ in Ukraine 200$, it is like in the usa 4000...5000$. Very glad I found your theme on the mini T2. all that is necessary for this version was bought. But the principle of the mini T2 is not clear to me, as a strange idea. for this I did not buy a board for the power supply. I did not buy the case. understand me correctly. do not want to spend money when you can not be sure that everything will work. I made all the stabilizers on a simpler circuit, with much less cost for it. i feed the incandescent separately, manually for now. after 60 seconds i feed all the other power. +220, +400, -460 do not come at once, they come gradually, with a rise in 100 seconds.

Thank you mwl168 for the opportunity to get the mini T2 boards. the package from mwl168 arrived on february 22nd, and on the 24th my country was attacked by the enemy. and everything went into the background, the country was fighting for survival. thanks very much to many countries, especially the USA, very much helped and helped. now there is already hope that my country will survive, and i hope that i can solder a mini T2 and listen to the potential of this version. Translated with www.DeepL.com/Translator (free version)

I bought the EL34 a long time ago, but I haven't bought the tube 6922 yet. Please recommend a brand for the 6922. P.S. I know a good specialist, he is not greedy and also shows his ideas. The master in 2019 offered an interesting variant of the amplifier for electrostats. https://ibb.co/SRpSDnJ But unfortunately I could not buy 10m90s so I decided to try to repeat the mini T2, where in the amplifier itself 10m90s is not necessary.

I assumed that the circuit with the two chips also deals with the gradual heating of the lamps, from about 2v and up to 6.3v/ 15....30sес. But it turns out that this is not the case. https://ibb.co/NW7GQwf then it is not clear why so many radio parts are involved. sorry.

jamesmking, Please write the gist of the 6.3 volts. I'm sorry, I don't understand everything. When you turn on your amplifier, you don't supply 6.3 volts at once to legs f5 and f4 of the 6922, but much less? And what happens at this time with the EL34 lamp heating?

jamesmking, sorry. I understand +400v and -460v. What I don't understand is where does +220v come from?

Sorry, What is it? I hover the cursor, a link appears, but nothing opens. I tried it on different browsers, but nothing opens.

Оgo! You surprised me, it turns out that the power supply has many functions. I would like to thank you very much for the explanation, of course it is necessary to study and try to understand the developers' ideas.

I looked. I saw two diagrams, but it is not clear to me which variant is intended for mini T2. And it is not clear why the mini variant is not in the topic of mini T2.

I looked it up, the transformers are approximately clear. thank you. I do not see in this thread the circuit diagram of the power supply for the mini.

Hello. A huge request to those who have done a miniТ2. I am interested in the parameters of the TOR transformer. how many volts at the output and the current strength

I watch and am amazed. you did everything very beautifully, both the installation and the case. Respect!