Total Domination VFET (TDV) Amp (using 2SK2087C)

[Jerdy]

just chill

buggers are tough

with 60W of heat you can use cardboard as isolator pad, and they'll endure, until wire is melting-desoldered from source

and then again

Say no more That's all the evidence I need.

 

[Zen Mod]

ok, just for the record - don't use cardboard as isolator pad

 

[ra7]

That made me laugh! Edit: that was for post 160.

 

[e_fortier]

Picture (Snapshot from video) of the BAF 2022, what a cute couple..👍

 

[codyt]

Those sinks look just about perfect for the TDV dissipation

 

[e_fortier]

Looks like 2U but the fins looks deeper than on a regular 40mm deep heatsink

 

[ra7]

Yup, that is it. Thanks for posting, Eric! The heatsinks are from Conrad Heatsinks (https://www.conradheatsinks.com/welcome.htm). I got them back in 2008 when I was just getting into this hobby. I bought a quad of them. They are superb quality. The 2U version was intended for a 10W JLH, which was never built. Instead, the love affair with Nelson began . I also have the 4U version, which I have brought out for the SCG power amp. They need to be tapped.

I can crank it to about 1.8 amps to get the TDV heatsinks screaming hot. The Tokin parts can be pushed to much higher bias, but about 8W is all I need at home. Originally had the Sony parts in there at about 1.6 amps. Easy-peasy for those sinks.

 

[von Ah]

Build is coming together In a mini Dissipante 3U 300.

I goofed when ordering the film caps and got 30x30mm bricks. Also my 2087Cs are a bit low on the heatsink, but I’m pushing forward with that.

I’d like to ask: is there anything glaringly off with this layout? Would it be Ok to arrange the inductors symmetrically at the back?

 

[e_fortier]

Hi Marc

Nice work, very encouraging.

Are these 2 small switching mode power supply (SMPS) ?
If so, have you had a chance to verify if your SMPS can handle such a big CRC filters ? Some SMPS go into hiccup mode and can’t start normally (it keeps trying) if the equivalent resistance from these capacitors is too low.
Nicely done, just try to keep your amplifier pcb as far as possible from your SMPS and AC mains.

It’s nice to see another one of these being built 👍

Rgds
Eric

 

[von Ah]

Thanks, Eric. Yes, I tested these SMPS with the cap boards shown a while ago as I was gathering things for a LuFo build. They powered up fine with no issues. That power supply got repurposed for this far simpler build.

https://www.diyaudio.com/community/threads/lufo-amp-39w-se-class-a-from-28v-rail.372679/post-7082254

If I’m lucky, this TDV will be powered up tomorrow for testing!

 

[e_fortier]

Awesome 👍

 

[Vunce]

Great point Eric, I was going to mention that also. A capMx with its slow start could be an option if the CRC is an issue for the SMPS's.
Looking good so far Marc!


Looks like my slow messaging missed your answer, LOL. Great news the supply is verified to work already

 

[von Ah]

These SMPS are MeanWell RPS-200-27-C. 200 watt, +27 VDC output (adjustable).
https://www.digikey.com/en/products/detail/mean-well-usa-inc/RPS-200-27-C/7706042?
Well regarded in the big Modulus-86 thread. Worked fine with the diyAudio Store power supply boards.

 

[codyt]

Looking good! FWIW, I tried the choke’s in both front and back positions and noticed only a slight reduction in noise when keeping them further from transformer. That said, I’m not sure how/if they’ll interact much with the SMPS’.

Regarding that TO-220 (I think) resistor at R3 - pay attention to how hot it gets. I know that some of those larger package resistors state big dissipation, but it usually depends on heat sinking them.

For instance, I checked some TO-247 Reidon resistors I have. They're rated at 30W (when sinked) and 3W (free air).

 

[von Ah]

Thanks, Cody. Very good advice. I may have a couple little sinks to use for those. They’re TO-126, 15W with sink, 1.25W free-air.
RTFM, Greenhorn.

 

[ra7]

Von Ah, looking great! Apart from the SMPS, layout looks good. Once you get it going, you could try different positions for the chokes. I have found that as long as they are away from the trafo, they are okay. Looking forward to the build!

 

[von Ah]

Dang, I forgot to isolate the screws through the SITs and heat sinks. Need to back those out and re-attach. Gotta love those moments when another thread reminds you of things you forgot.

 

[Zen Mod]

if 2SK2087 is in, no need for that

body/hole is isolated

same as IRFP240, for instance

 

[von Ah]

Excellent, thank you, ZM!

 

[von Ah]

First power on is a success! Woo hoo!

Now, what’s the easiest way to check the bias?

27.8 VDC going to the boards. 1mV DC offset. Sinks getting warm, maybe ~45C. 1.1 and 1.2 VDC going to the inductors.

R3 is really hard to get to.