JoaMat

Now when Kerry regulators and psu board are on its way I and maybe a few other builders wonder what transformers might be appropriate. James, @jamesmking, what transformers did you acquired for your mini T2?

A version of mini T2 with active batteries. Battery has lt1021 voltage reference and a current sink ensures it works properly. Under batteries and input tubes is a small circuit (in the yellow circle) – same circuit in DIY T2 has five 2sc3675. Only exists in fantasy.

Some progress. Replaces the original battery in my DIY T2, which was supposed not to be modified in any way… Schematic:

Try those modern components and reduce high voltages to +/-400V (I’ve tried all except KSC1008 and J112). Old Modern 2SA1468 KSA1156 2SK216 KSC2690A 2SJ79 KSA1220A 2SC3381 KSC1008 2SK246 J112 2SK3675 FJPF2145 Mouser wants $51,51.

Looks very nice. I like the negative regulator. Milled today. Board has 13 vias and I think I've found a good way to make it in our kitchen (turnaround time is an hour or so (more likely a couple of hours)). STN9360 is too big for this board. STR2550 is much smaller and there is room for four of them plus LT1021, 10M90S, HN4C51J and a few other components on the other side.

Now printed stencil 0.2 mm thick and I don’t think it will work, not with my printer anyway, a Prusa i3. Printer has big difficulties with small footprints as so-23 and sot-26. The others might work… maybe, not sure. Also the side towards pcb is to rough.

Money sent, thanks.

Print this file mini T2 left top stencil.zip in 3D printer and see if it is useful as a stencil (top layer left channel). I've never ever done this stl file is created by https://solder-stencil.me/.

I guess most of the parts on underside will stay in place by surface tension. If they fall down don’t blame me – put blame on Newton. Anyhow, I held pcb upside-down and blow 360C at flow 5 for five minutes and 0805 resistors and HN4A51J stayed put while solder was liquid so I could move them off with a tweezer. For me the most difficult is to put the right amount paste on pads, it easily become very messy…

Thanks. Now I’ve done some more practice. First solder with leaded solder and then with lead free. Guess I prefer leaded as it’s faster and a bit easier. Trying different settings. 300C and air flow at 5 seems to work with small parts and leaded paste. I can do it all with one hand. 1; solder paste on pads. 2; put component with tweezer on pasted pads. 3; blow hot air till paste melts and sucks component nicely in place on pads. Only right hand is needed. One hand left for... a good cigarr…

OK, I'm trying and hopefully learning something, with solder paste and component in place and then hot air. What temperature and airflow did you use? Also what type of solder paste?

Michael, Add 2 mini T2 boards. Thank you, Joachim

A few years ago I bought a Weller hot air station WTHA 1. It was my first hot air station and I thought it was a good station. It was quite expensive so it had to be good! Suddenly the display showed “Error 3” and nothing more happened. No guarantee left and I couldn’t remember from whom I bought that crap from. After some investigation I bought a Quick 861DW. Now I’ve used the Quick for a while and I’m very happy with it and it costs a third of the Weller - and ten times better. I use a Weller!! solder station for smd soldering and have no intention to change that. But when working with the Quick hot air station the last days I tried to solder components with the Quick and it did work quite well. So, first I thought this is a complicated way to solder smd parts.. … but I now I’ve changed my mind, well worth trying – Thanks for sharing this, James.

Nice! I like them chassis.

Milled a new “corrected” board on Sunday. When populated and ready for test the bloody thing worked fine for a few seconds than it started to decrease voltage slowly down to 230 volt or so. I started to change component by component and when just a few unchanged I replaced the dn2540 and issue solved, phuuu. Anyhow. Now the regulator seems to work alright, okey just 10 – 12 mA of load. With trimmer (200R) there is a range of 5V at 400V. Picture shows 400.0V and after 20 minutes the meter in “minmax” says average 400.0V within -0.0/+0.1.