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21st Century Maida Regulator

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#681
I recommend this scheme:
MaidaReg_R3p0_ASSY.jpg


You can find it for sale here: https://neurochrome.com/products/21st-century-maida-regulator

If you'd rather design your own, there're plenty of schematics in this thread to draw inspiration from. But expecting me to give away my work in a vendor thread seems a tad much.

Tom
 
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#682
Hi, all
Can you help me look at this schematic to see if there is anything wrong? This config should give me 170V output but as i increase input voltage, output voltage also increase. Seem like output voltage ~= input voltage - 60V.
Thanks!
 

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#685
You're right. That should work. I get just shy of 2 mA through R6, so 160 V across R9, thereby, 170 V at the output.

I do recall fiddling with that a while back and settling on a lower voltage across R7.

It would be interesting to build it and see if it's a simulation issue or if the regulator just explodes on start-up. Wear eye protection. 🙂

Tom
 
#687
You can also buy the latest revision of the 21st Century Maida Regulator here: https://neurochrome.com/products/21st-century-maida-regulator

That Regulator has been updated quite a few times since the original design. The first update (to Rev. 2.0) made significant improvements in the line rejection (i.e., ripple rejection of the Regulator). The subsequent updates were to further enhance the ruggedness of the Regulator.

Tom
 
#690
Hi! I need some help with suitable parts. 🙂
If we look at this schematic then would be ok to use for M1 also STW30N80K5 instead of STW11NM80? Using with 300V input. For D2 I have in hand MURHS160T3G diodes. Would that also be ok to use? It has bigger reverse current 180 mA compared to diodes MURS120 (Ir 2 uA) and 1N4007 (Ir 5 uA). Does it matters in this Maida design?

1720041711004.png
 
#691
Are you sure of that reverse current? 180 mA sounds more like a forward current. D2 is just to discharge C1 when the regulator turns off. Without it you risk frying the regulator IC. It can be any diode. I use 1N4007.

The MOSFET needs to be able to survive the peak inrush power. I use a beefy SiC type in my current design, which is available here: https://neurochrome.com/products/21st-century-maida-regulator. But if you're planning for a lower output current, you could relax the requirements a bit.

Tom
 
#693
I need some help please with this regulator using schematic posted in #690 post. Input voltage 314 V and output voltage about 310 V (no load). Trimmer is not regulating voltage. R1 is 10 ohm, D3 is 6.8 V zener, R8 is 5.11k ohm, M1 is STW30N80K5 (10 V zener between S and G). I use NTC SL22 (20 ohm) before toroidal transformer. What should I check or change in this regulator to get this regulator working between 200-250 V?

STW30N80K5 SOA graph:
1720288259417.png
 
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#695
Tom, thank you for pointing that R4 out. I tried to lower R4 to 94k ohm and I still have the same output about 301 V.
I measured some reference voltages. In dc 308 V, Mosfet Gate 304 V, Out 301 V. LT3080 set 302 V, in 303 V.

What to check or test next?
 
#697
I've only recently discovered this product and it looks like it will serve my purpose for when I build up the Joe Rasmusen FVP6 circuit.

My question is how to determine how much heatsinking I will need.

I estimate total draw for phono and line stage to be no more than 20-30mA. Raw DC input will likely be 300V or so for 250V out.

Could I get by with a piece of 1/4-3/8 aluminum bar stock about an inch or so longer than the mounting plate.


As an extra curiosity how does this regulator implementation compare to Allen Wrights long time circuit the Super Reg?

Is it ok to use a single regulator to power both channels of a tube phono and line stage?
 
#699
jasonb84 said:
I've only recently discovered this product and it looks like it will serve my purpose for when I build up the Joe Rasmusen FVP6 circuit.

My question is how to determine how much heatsinking I will need.

I estimate total draw for phono and line stage to be no more than 20-30mA. Raw DC input will likely be 300V or so for 250V out.

Could I get by with a piece of 1/4-3/8 aluminum bar stock about an inch or so longer than the mounting plate.
Click to expand...
Here's a heatsink nomograph from Radio Electronics decades and decades ago:
1724167491387.png
 
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#700
jasonb84 said:
I estimate total draw for phono and line stage to be no more than 20-30mA. Raw DC input will likely be 300V or so for 250V out.
Click to expand...
30 mA output current, 300 V input, 250 V output -> Power dissipated: Pdiss = (Vin-Vout)*Iout -> Pdiss = (300-250)*0.03 = 1.5 [W].

If you're using an external heat sink I'd limit its temperature to 60 ºC so you don't burn your fingers if you touch it. Or maybe 45-50 ºC if you use the top plate of the chassis. Assuming 25 ºC ambient, this means you can allow for about 20 ºC temperature rise (45-25 = 20). So you'd need a heat sink with a thermal resistance of 20/1.5 = 13.3 ºC/W or better (lower).

The mounting plate measures 8.5 square inches. I forget the thickness. It's either 1/8" or 0.10". Either way you're looking at about 6 ºC/W or better, so you can get away with just using the mounting plate as the heat sink. I'd bolt it to the chassis wall (assuming the chassis is aluminum).

jasonb84 said:
Is it ok to use a single regulator to power both channels of a tube phono and line stage?
Click to expand...
Yep.

Tom
 
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