I got approached by PCBway who wanted to sponsor a batch of assembled prototypes, and i just received them and fired them up!! I wanted them without the inductor and tube holders because i want to experiment a bit with different tubes, and to check if i could use some smaller inductors

The assembled boards look beautiful! And they booted up perfectly, and thanks to the dtr/rts boot/rst transistor they program directly through USB-C without having to push any buttons., if you want one ive added the project to PCBway Projects, so its pretty easy to get one there.

Boards with tubes:

Since i finally got some prototypes to test out i dug down in my tube collection and found a SBM-20 which it is designed for accepting directly with mounted 6.5mm fuse holders, but i also have a huge SBM-19 and a pancake SI-14 Ive always wanted to check out.

SBM-20

This is what it is designed for, the small portable SBM-20 tubes, They are quite cheap, i think i paid about 15$ per piece from an Ebay seller in ukraine. They run at around 240-280v, (with the 22mh inductor i get that around 25% pwm @1000hz) and they give about 20 clicks per minute, since the power supply is software configurable, its just a matter of sending "VOxxx" commands over serial until i start to get ticks, and then i increase it a little bit. the sbm-20 tubes i usually run around VO400.

I also wanted to upgrade the case, Ive made a 2 part snap fit 3d printed case, the old one weren't very water resistant if i wanted to use them outdoors, so Ive recessed the USB hole so i can pot the cable in place, and made the lid lip go a little bit further over the main case. I also designed some brackets for wall mounting.

SBM-19

Next i wanted to test out my SBM-19 tube! This is a beast, 195mm long and 19mm in diameter, running at 350-375V and gives out a nice 80-90CPM, so it sounds very geigery with multiple clicks per second just from background radiation. The fuse-holders fit on the tube terminals, but i had to solder some wires to the board

I allso made a snapfit case for this tube , its based on the SBM-20 case but much larger, and an internal cutout for the tube and fuse holder

The next in line is to make a battery driver version with a screen using the SI-14b pancake tube! So looking forward to that.

Below are some macro shots of the board: