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Someone noticed the d-_-b airplane 🤣

Once properly warmed up for an hour or so, the transistor legs sit at around 110, transistor casing at 100 and hottest part of plastic tab at 90 (all in degrees Celsius and with at least +/- 5 degrees or error possible; the IR-gun I use is not the most sophisticated). Definitely too hot to touch, though still a bit cooler than the EL34s . So a bit of margin on both die temperature and what PLA Pro can withstand, though I guess the latter will age quite a bit faster than it would at ambient temperature if I would leave the amp turned on 24/7. I normally don't post pictures because my case work is rather poor, but I found a long exposure mode on my phone which after some experimentation captures the tube glow without leaving the rest in darkness, so I thought I'd make an exception. Pardon the somewhat battered front panel. Should also add that it sounds great.

Unholy carp, it's Ren, doing a different song than "Hi Ren", and well!

New solid state CCS for Megatron. Now with a third pin for ground. The pins are made from 2.5 mm brass rod, which is almost 0.10 mm thicker than tube pins. PCB is a CNC milled one side 1.5 mm copper clad. So, no copper on top side of PCB. Holes for the three pins are 1.0 mm deep and you have 0.5 mm epoxy laminates left. Transistor pins are protected with heat shrink tube and the exposed metal tab is protected with a 3D printed cover. The screw holding transistor to heat sink is electrical connected to it and to the ground pin. The white base with guide pin is made of three 3D printed parts.

Fan of this kid. Very sardonic sensibility and seems to really care about the musicianship.

12 years from this:

Thanks for your comments, @simmconn. The heatsink gets warm and user is aware of it. I think he is running at 400V/22mA and so far, it seems to work. If it gets too hot than he can’t use this thing - that’s life. For pin dimension. The first version used Neutrik XLR3 pins. They were perfect, diameter slightly undersized. But to short to be soldered direct to main PCB. When looking for brass rod the best I found was 2.5 mm so, I decided to try that. 2.5 mm works with my Teflon tube sockets. The user is informed of that pins are soldered only on one side and if pins come loose, we have to find a better solution or perhaps abandon this thing. I use Addnorth HT-PLA Pro filament. Better heat performance than PLA but not as good as ABS. I’m confident the socket isn’t a problem. It might be a problem with the transistor tab cover. I haven’t thought about the cover until your post - thank you simmconn. Now the user is informed, and he promised to keep an eye on the cover.

Interesting design! I’d be a bit worried about the thermal and mechanical side of things. The thermal resistance of the heatsink this size is probably going to run above 5C/W without forced air flow. It is going to run too hot to touch at 350V to 400V/20mA (7 to 8W). With 3C/W theta JC on the 10M90S, there is still margin on the die temperature. If I were to design a PCB to be plugged into a tube socket with soldered pins, I’d use slightly undersized pins and whatever copper I can get for adhesion to the board (double layered board with plated-thought holes in 2-mm or thicker PCB), especially if the counterpart is the unforgiving “modern” tube sockets with tulip type spring contacts. Last but not least, when the whole thing gets very warm, I’d use materials with higher working temperature such as ASA or ABS. PLA is probably not going to last very long.

^^Yup.

I like the idea of dessert on the house. As do the local cats

Fresh Fish

Alec's been on a big 90s alt rock kick and has been sending me some stuff I'd honestly completely forgotten.

Your presence there is not going unnoticed.