JoaMat

The beauty of making your own boards. Really nice.

Great that you got a more stable driver by removing the servo. After a closer look at what you have done I think the servo needs to be further modified to work. My experience is that the opto servo on the KGSShv Carbon works perfect. I use the same opto servo on my SMD Grounded Grid except I changed pzta06 to a to-126 device and removed the trimmer and its serial resistor and that servo works without any drift – high voltage 400, 450 or 500 volts, output current 10 – 20 mA still no drift and offset fixed at zero volts. The driver will probably work as you have it now. Let it get warm and stabilized before turning on the output for the first time for adjusting. One might consider to have the driver on and working while turning on/off the output…

Maybe I got it all wrong but I think that the modification suggested by Soren, beside onboard feedbacks, is an onboard offset servo. My idea is to have a fixed offset at zero. Then you can concentrate on the outboard (version 2) and its PSUs, preferable with help of a variac. From my experience (very limited though) is if something goes wrong neither zeners nor current limiter will save you from flying black fragments. If you just are looking for some excitement you can try joggling three bottles of nitroglycerine.

You can’t get the servo to work? The opto servo on the normal Carbon controls the offset perfect – no drift.

Just curious. Did you use back to back zeners on the output mosfets suggested by Soren and Kevin? Also what value of the current sense resistors - 5.1 ohms or 12 ohms for "further protection”?

Very nice! Low voltage +/-18 volts, right?

I’m actually a bit surprised that it didn’t explode at +450V. From memory - according simulation I’ve done in LTspice I think it will all explode at +450V and probably even at +15V. The unsuccessful work I’ve done on the Circlotron is with the first generation servo.

Sorry for your second failure. After my own failures I've been like gun-shy dog – haven’t touched the Circlotron project for a year. But there must be a way to get the Circlotron safe even for the common DIYers, mustn’t it?

Thanks for the information. I have made some attempts with the Circlotron. Blown both PSUs and outputs. Small black fragments all over the place. Seems that things easily might get wrong and then both PSU and output are effected.

@Tinkerer,Sorry for your accident. Did something broke on the output board?

Has anyone tried the low voltage supplies on the HV boards with AMB’s Sigma 78/79 regulators? I think it would be a simple and not very expensive improvement.

I run my mini Dynalo at +/-20 volts. AMB voltage regulators, positive 10K and 133K, negative 10k and 160K resistors.

https://tubedepot.com/ - Claim they match up to 9 tubes for free??? Also have Philips Miniwatt metal base tubes.

Nice! 18.5 mA through output transistors? Nearly 2.5 W each.

I had 0.1uF wima in mind, but i'is to low?

I guess the 35uF electrolytic are on the board for some reason – why?

I'm going to feed ducks, sometime.

Brainstorm - Output transistor on bottom side and the other components on the top. There are some 300V and even 400V sot-23 devices.

not possible, I am several hours ahead of you Americans

You don’t want the male pins be exposed with voltage on them. Imagine your 2 years old grandchild about to explore the world and found the exposed kV pins. IMO it’s not necessary to separate filament wires from the others.

Yes, that’s copper clad. I’ve a CNC machine. Nice opportunity to learn have to use it. I’m not ready to mill aluminum yet.

don't hold it for to long, it might get old

I think it might be possible to squeeze in a digital attenuator in Mini Dynalo. ATtiny85 is in the middle of the breadboard, lots of space for it in the box. Need some 5 volt supply as well.

Right, no volume control - also the way it should be.

I said a few days ago that I’ve given up Attiny85 as controller for the digital attenuator. I’ve done some additional attempts today and it turns out to work all right. I really like that little thing. Can’t be more minimalistic..? Regarding pops/clicks I think I've to give up. Seems to be to complicated for me to solve.