JoaMat

Probably because the 5V doesn’t like shunt mode. From LT1021 datasheet: Three voltages are available: 5V, 7V and 10V. The 7V and 10V units can be used as shunt regulators (two-terminal zeners) with the same precision characteristics as the three-terminal connection.

Transformers in the front (other reason than above though). You like the wiring? Size is huge. Angel brackets adds to much thermal resistance and add space.

Great! T2 current sources with c4686 instead of c3675?

Have you tried the opto servo?

Did this one today. Layout file name is JimL_CS.LYT.

Yep, that’s right. Tried to be smart. Set the cut depth to shallow at first. Ordered the machine to clean up a small area…. and at the same time it cut the trace near that pad. Learning by doing...

I agree with John. Amazing front plate you have done, Kerry. Today I built a T2 servo on a small board. It’s now doing service on an original DYI T2 and seems to work OK. If it really works the layout will be implemented in a new version of DIY T2. Also give me opportunity to learn milling PCBs on a small CNC machine – indeed a funny toy. Did a small mistake - can you find error in below pictures?

Don’t remember the exact words, but she is a very adorable partner. Got this as a present recently………

...fifty free hours, then

Happy Birthday!

Last few days I’ve had some annoying noise from one channel of my Grounded Grid. After a few hours on surgery table I found this three small resistors…. …..obviously I missed solder them on both ends. I’ve used the amplifier like this for almost four weeks before the noise started.

Here is an original T2 with Kevin’s optocoupler servo. Servo is on a small board, replaces one of the 2SC3675 in Darlington pair. Works well…. so far.

With SiC I don't use any shoulder washer, just metal screw - torque set to 81 Ncm on the scale.

4180G

Looks insulated but bottom is not. I use aluminum oxide insulating washer and steel screw. Avoid conductive thermal grease.

If you use the correct shoulder washer and don't smear the junction with conductive thermal grease than it's safe to use steel screw.

Nicely done. That one is a small one. But else surface mount isn’t that difficult, with some practice…. and it's fun.

Once I cleaned a straight six BMW cylinder head in dishwasher. Very handy.

Anyone tried dishwasher?

Glad to hear it was that easy get rid of the oscillation. My idea is to build a version with ksa1220/ksc2690 replacing the old and hard to get mosfets. Have listen to an original DIY T2 with the mosfets replaced for a week. My impression is that it works well.

Good news. What was the problem and its solution? Might be valuable information for us.

This is my modified T2 from 2014. Later further modified with Cascaded CC a la JimL, replaced a bunch of to92 with small smd ants and replaced one battery with, an all SMD battery on a small daughter board. No oscillation, no hum or other issues. Works equally good as the three original T2s I’ve built. I frequently make layouts, mirrored or symmetrical and make the boards in our kitchen. For me it’s a hobby and I’m really enjoying it.

Did this last night, not finished yet. Modified T2 output section. All parts available at Mouser. SMD give space for bracket. Board size 150mm x 100mm. Darlington pair in the middle, one on heat sink and partner standing. Below: draft of an input board. Right/left channels will be mirrored.

IMO split washer is good enough in T2.

Get a working T2 needs a little more than pure luck........... Glad noise is solved. I use 7721-3PPSG whenever insulation is needed. First I considered drilling but tried pressing the shoulder in place be means of a small vise. Pressing turned out to work all right . Set torque by feeling of wrist, but last year I’ve used a Swiss made torque screw driver with torque set to 0.8 nm. Steel screw is what I use.