Inu

I think your next birthday gift from her is a caring case for these.

It

With and Without servo

Only one in UK!

I wish no word

Congratulation!

No oscillation but I added 500ohm to the K216 Gate. Picasa Web Albums - inuponken - T2

Uploaded. Picasa Web Albums - inuponken - T2

For the ultimate DIY? A Curve Tracer!

I have counterfeit K216. I will take a photo later.

I am using a trick that inserts tubes into the sockets completely then pulls tubes for 2 to 3mm upward. Added 5PF Dipped Mica to the NFB resistors to reduce overshoot at 10KHz and...

I have a same static noise problem. When tapped top of the 6DJ8 lightly, the noise stops. I thought tube is bad, but no problem on the other amp... I am going to replace the tube sockets.

Q4 and Q5 are OFF? Check Q1,2,3, D2, D3, R1,2,3 with multimeter at power OFF. To confirm 1.2V across R1, R2 and R3 (5mA/2.5mA/5mA). Swap 6DJ8’s...

My 20-16164 is the same configuration, only two lines of ventilation holes on the bottom. I am using this case for my breadboard-KGSS

FYI I measured hfe for all transistors before use on the T2. 2SC3675 Measured: 74pcs @Ic=10mA Lowest = 43 Highest =74 Average = 58 I used hfe=57@10mA for 4xQ23 2SC4686A Measured: 50pcs Lowest = 22 Highest =31 Average = 27 I did not use because of low hfe.

Correct. I assigned |B| for Low bias line.

I have never seen the counterfeit MOS FET yet but many of Japanese small signal transistors. 2SC2240, 2SA970 etc… purchased from MC… M.

Following is adjusting procedure that I am using. Presetting: Set RV2 to Center, RV1 to up (= Wiper is R32 side) position. Confirm voltages between +/- Output and Output to GND are not too High (< 80V) If voltage between Out to GND is too high (300 -400V), prepare to replace the 2SK216s. if around 160V, check 100V zener diodes. Set both batteries to 740V with RV2. Adjust RV2 alternately (2-3V step each and upward) to Output

Avoid 6N1P and 6N11. These are different animal. These are bad linearity with the low voltage (<100V) operation.

In my experience, You will be better to check the 6DJ8 if you using a vintage Ampelex. My old Bugle boy killed 2SK216s twice so. If you use the unbalanced or low-Ip 6DJ8, you will be into the mud. I am stop using the vintage tubes for the T2, happy with the Silvania tubes now. As Kevin mentioned before, adjust Active Battery is tricky. While adjusting the active batteries, you will better to monitoring voltage between +/-Out to GND or +Out / -Out at same time. Not necessary to adjust it to exact 740V. My unit is balanced at 749

How about 2SA1831? Not isolation package and Vceo & Vcbo are 100v lower than 2SA1968LS but cob is smaller than 2SA1968LS. 50pcs (= minimum order: >$50) @$1.41 100pcs @1.06 http://www.tenfourltd.com

Thank you for your advice. The noise (ripple) that I am trying to reduce is generating in the NFB loop. I got a same result on the LTspice so I will conclude this issue. I tried to use several OP amps OP27(TI), LF351(NS), OP07(AD), OPA177(AD), so far OP27(TI) is the best on my PS.

Small cap wouldn’t help to stop the “switching” 2SC3675. In my case, I changed R14, R29, R41 and R53 to 33Kohm to stop the "switching". Now all lines are stable and very quiet. My OP27 is PMI “OP27GZ”.