The Quest for >2000 Vppss

[kevin gilmore]

the power of that part is 170mw.  so the stn0214 should work. make sure the pinout is correct.

mouser has thousands of ksc5026 in stock.

the extra diode cannot hurt. not sure what it is supposed to do.

[Craig Sawyers]

On 12/27/2025 at 7:06 PM, MLA said:

Test build of Super-Carbon up and running to see what is what: 

 

PSU angle brackets are recycled from a previous, very tight, build, where those cutouts made perfect sense . 

Two small issues worth mentioning on amp boards. First, TTC004b and PZTA42 have opposite pinouts (ECB vs BCE) so if using TTC004b, transistor front needs to face heat sink. Second, you need to add some current limiting on the CS LEDs if you intend to use them.

Running at +/-550V. 

No listening yet; need to build a more permanent CS supply solution first and also tidy up in general.      

  

As soon as you guys start using IMGUR, we cannot see content in the UK. This is because the UK on-line regulator OFCOM is suing IMGUR as a result of lack of assurance regarding harmful content to minors (AKA under 18!). IMGUR has responded by simply showing a blue screen with "Content not viewable in your region" in large letters. 

This describes the decision https://www.bbc.co.uk/news/articles/c4gzxv5gy3qo

IMGUR images look like this from the UK

[jamesmking]

3 minutes ago, Craig Sawyers said:

As soon as you guys start using IMGUR, we cannot see content in the UK. This is because the UK on-line regulator OFCOM is suing IMGUR as a result of lack of assurance regarding harmful content to minors (AKA under 18!). IMGUR has responded by simply showing a blue screen with "Content not viewable in your region" in large letters. 

This describes the decision https://www.bbc.co.uk/news/articles/c4gzxv5gy3qo

IMGUR images look like this from the UK

personally I set my vpn tunnel location to the USA and then I can see the images... at least until the uk makes vpn tunnels illegal...

[MLA]

35 minutes ago, Craig Sawyers said:

IMGUR images look like this from the UK

Somewhat ironic - since I'm not in the UK, your post is showing me exactly the same amplifier picture I posted earlier :).

I see the problem though and I think it's been brough up before in this forum. I was hoping for Imgur to resolve this, but if it persists and/or spreads I might look for another image host.

[Shawn]

 

1 hour ago, Craig Sawyers said:

As soon as you guys start using IMGUR, we cannot see content in the UK. This is because the UK on-line regulator OFCOM is suing IMGUR as a result of lack of assurance regarding harmful content to minors (AKA under 18!). IMGUR has responded by simply showing a blue screen with "Content not viewable in your region" in large letters. 

This describes the decision https://www.bbc.co.uk/news/articles/c4gzxv5gy3qo

IMGUR images look like this from the UK

Here you go. I forward the previous pic. Should be visible now.

[kevin gilmore]

board updated with extra diode.  in the stax mafia google shares

 

[Craig Sawyers]

12 hours ago, Shawn said:

 

Here you go. I forward the previous pic. Should be visible now.

 

Excellent - thanks!

I'm only sorry we have such dick head regulators in our small island, spoiling IMGUR access for the 65 million crammed in to our speck of dirt.

[Shawn]

Roughly based on the schematic Kevin provided (Based on the version with the extra 1N4007 diode), I did an SMD layout of the circlotron PSU.

Yes, it looks familiar. The layout was adapted from the GRHV SMD board and modified for this application. The board size is 51 mm × 31 mm.

The KSC5026 was replaced with STN0214, using a large copper pad underneath for heat dissipation.

The 10 Ω / 5 W resistor can also be substituted with 4.7 Ω, which is generally easier to source.

Don`t know if the two stn0214s can be replaced by PBHV2160.

[kevin gilmore]

edit: removed, looking at the wrong schematic.

 

Edited Saturday at 11:07 PM by kevin gilmore

[MLA]

Picture from work in progress (if there ever was anything else). I can now start the Super-Carbon without using the Variac.

 

Initially, the PSU SicFets blew up during startup when doing a full power on, very similar to what SimmConn reported here:

Presumably my SicFets ventured outside their SoA during startup. I'm not using the Cree C2Ms here (though it's a similar spec'd SicFet) and I have the current sources set for 25mA which might be pushing things a bit, so this particular problem may very well be unique to my build.

However, since this forum has a lot of clever participants , the solution was at hand in the same thread. As per @Kerry's advice, I wired in the depletion mode MosFet current limiter directly after the pre-reg caps instead of having it after the post-reg caps. Also, I added a Vds clamping Zener as per @simmconn's mod.

Not skilled enough to tell which mod did the trick or if both are necessary (and one can of course never exclude the possibility that it now works for some other reason that I have no idea about), but anyway it now starts up without anything blowing up and I can move on to the "oh, I'm supposed to listen to it?" bit. Special thanks to Kerry and SimmConn (in addition to Kevin designing these things in the first place); I would not have figured this out without you!        

 

Apologies to all UK members; haven't gotten around to finding a new picture host yet. 

Edited 16 hours ago by MLA

[Shawn]

7 hours ago, MLA said:

I wired in the depletion mode MosFet current limiter directly after the pre-reg caps instead of having it after the post-reg caps. Also, I added a Vds clamping Zener as per @simmconn's mod.

I believe Q12 (IXTH6N100) here is also acting as a current limiter, and it’s a depletion-mode MOSFET.

I’ve been thinking about slightly changing its placement: moving it ahead of Q2 (C2M), after the filtering stage. Since the C2M devices are now discontinued, they’re likely to become increasingly difficult to source going forward.

[MLA]

I realise I was a bit unclear above. The Q12 IXTH6N100 is indeed a current limiter and as I read the schematic, it's there to protect the whole psu should the amp board develop a short of some type. 

So what I did above was "steal" my Q12 by re-wiring it for start-up duties instead (placing it between pre-reg caps and Q8).

However, that also means that my boards no longer have the Q12-based psu protection in place. So in the future, I will probably put a second IXTH6N100 on the board (in the Q12 position) to restore that protection.

 Also, you don't specifically need the out of production C2M parts for the psu. The next generation of those SicFets, specifically the current production C3M0900170D that also replaces the old C2Ms on the amp boards, work just fine.

[Shawn]

1 hour ago, MLA said:

I realise I was a bit unclear above. The Q12 IXTH6N100 is indeed a current limiter and as I read the schematic, it's there to protect the whole psu should the amp board develop a short of some type. 

Sorry. I didn’t read your post carefully enough the first time. Glad you’ve got a working solution.

My current thinking is: instead of keeping Q12 at the very end of the PSU, I’m considering moving it right after the rectifier and bulk filtering, and ahead of the C2M device. For the SMD version, I’m also thinking about adding a STR1550 locally next to the C2M to provide a second layer of current limiting. That said, as mentioned before, similar to something like a 2N3094, but who knows if it works or not.

The main goal of the SMD redesign right now is to merge the two circlotron PSU boards into a single board and reduce the overall size by roughly half. If space allows, I’d also like to see whether the 15 V golden reference and the CPC1117 delay / soft-start can be integrated onto the same board.

I have some ideas sketched out, but I haven’t started any actual layout work yet.🤐