JoaMat

Good example of how to put a 2sk209 (sot23 device) on a to92 foot. I presume you can do a similar thing with ttc004 or ksc2690 on a pzta46 foot, they have the same pad c/c distance.

Another option – try 25K resistors instead of the 20K and tell us if you hear any difference.

Just want to add that the bias control is not my invention. You find similar on Uberamp and AMB’s beta22. My view on Copyright is - my right, as DIY:er, to “copy and paste” as I wish.

Added a NPN, a trimmer and some resistor. With those it should be possible to set current through output transistors. Well, that’s the idea. If it works I probably let you know…

Senior HeadCase member MLA has lent me his Dynahi. A week listening to it have convinced me that one actually can listen to non-electrostatic headphones. So here is my first attempt... ... a balanced something with lsj689 and lsk489. And as always everything I make is based on a Kevin design. In this case on the famous Dynahi.

Happy Birthday!

They are R23/34 in schematic: dynahibal1.pdf

Circled 50R resistors seem to have been 100R in earlier versions of Dynahi. What might the reason for the change be?

Group of the 3 Devils (D3): Russia, China and Iran. Who are the additional candidates for D8 and D20?

My simple brain thinks that the democratic world and its financial systems have cultivated Putin, his oligarchs and strongmen as sourdoughs. Now Russia is capable to destroy life for millions of people if NATO doesn’t engage. If NATO engage Putin’s only defense/threat is nuclear weapons. God bless us all!

Happy Birthday!

Seems to be a good solution. Thank you.

Slow progress, but finally I have something. mini T2 with Emission Labs tubes. It passed all tests in Proteus so it should work. If it blows up, . That must not happen.

Happy Birthday, Steve!

Congratulations to your New Company and I wish you and your cousin a great success, Kerry.

There are some posts on this subject on page 4 this thread.

Played on a Pleyel Grand Piano from 1836 - info.

That’s what makes this hobby so interesting. You need an open mind and a good nose to find replacements…

a sweep by Xi Jinping?

Thank you. Eventually I found it, among a lot of other stuff. A test board for the battery module. I probably did it in spring 2020. Left heat sink has FJPF2145 (org. T2 it's 2SC3675) and right has 10M90S current sink set to 5 mA. Just find +250V and -560V and you are ready to go.

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The above misfortune was due to a battery problem in T2 amplifier. I replaced a mosfet j112(2sk246) and left the 10K trimmer in max position. My guess (I’m just an amateur but this is my theory) is the battery with the new mosfet tried to set voltage to more then 100V lower than expected. Resulting in damages to Q5, Q23, Q26 and D23 along with damages to the power supply. In order to find out what voltage cross 22R resistor R42 I put 27V from lab PSU from R42 to RV2 with 10K resistor in series. When measuring voltage cross 22K resistor of each battery I got 1V lower value at the battery with the new mosfet then the other three. That’s why I think there was more than 100V lower voltage at that battery. Now I have gotten really tiered of led batteries so I removed them and replaced them with those daughter boards. The amplifier has only modern components. To my ears it now works as good as the original DIY T2.

Well, today I swinged my driver really hard and hit and killed +250v and -500V sections. Here are the casualties… …RIP. While repairing I also replaced ksc5026 in 250v section with 2sc3675 and that seems to work all right. Can you find them? By the way – the first version of KGSShv power supply used 2sc3380 along with 2sa1486, later replaced by ksc5026 and ksa1156 plus a Zener diode.

Man or mouse? I always start with the Driver. https://www.youtube.com/watch?v=J2RoYgRhXjw

Thanks James, my clock always tends to speed up when an amplifier needs attention. I have never used a variac when testing an amplifier. That’s way I asked.