'E-choke' Filter Boards

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Mike H
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#46

Post by Mike H »

@ Nick yeah that heatsink seems identical to Rapid's one, also supposed to be 1 inch lug spacing as well. I made mine 1.4 inches wide to be generous but in reality more like 1.35 as your drawing I believe. I'll find out as and when the real ones arrive in the post


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#47

Post by Mike H »

And there he is in situ. (grey outline)

Proper job. :D

Ta also for providing the RS No. I did look but was totally bewildered by the huge range of different variations LOL
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Mike H
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#48

Post by Mike H »

Application circuit ~
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#49

Post by colin.hepburn »

OK so does the E Choke require component value changes to it for different HT voltages let's say between the range of 200/300/400 volts and although intended to replace a standard 10H choke can it still be used in conjunction with a 10H choke as well to assist on what the 10H choke is doing maybe :?
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#50

Post by Dave the bass »

Mike H wrote:Application circuit ~
The way the cct is shown ... wont the rectifier see that big cap 1st? Fizzle pop bang?

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#51

Post by Mike H »

Don't they usually? Image (not fizzle pop bang)

It's the reservoir cap, petal.


Bless 'im... :D


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#52

Post by Dave the bass »

But that big though?

Spec on GZ34 for cap input PSU is 60uF max but for summat like an 83 MVR wouldn't that fizzle pop bang the blighter?
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#53

Post by Nick »

If you are using valve rect's then use a cap to match. The resulting first stage ripple will be higher, so a larger valve zener will be needed to match.
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#54

Post by Dave the bass »

Aaaah, I see, thanks Nick. I automatically assumed Valve recs. Wrong of me I know now.

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#55

Post by Mike H »

Yeah that's just an example, the reservoir cap value is, whatever.

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#56

Post by ed »

apologies if this has been asked before....cant find the description thread...

to use this in psud do we just sub a 10h choke...?..any significant resistance?
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#57

Post by Mike H »

colin.hepburn wrote:OK so does the E Choke require component value changes to it for different HT voltages let's say between the range of 200/300/400 volts and although intended to replace a standard 10H choke can it still be used in conjunction with a 10H choke as well to assist on what the 10H choke is doing maybe :?
Sorry only just seen this ~ 630VDC max. and that's only because of the 'stock' item for C1, replace it or omit it and connect summat else to 'CG' then whatever Voltage you can manage.

Going the other way, down to 50V or even less should be no problem in theory. Only need to make sure of a working V-drop across the device, = ZD1 + gate bias. Bu-ut R1 is best reduced in proportion, so if much less than 200V I would say reduce R1 to 100k.

'Spect you can add a proper choke as well but problee with an extra cap after it, not sure what it'll make of having an inductor feeding into it, probably a waste of time without an extra cap on the output side of the choke.

Does that make sense?

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#58

Post by Nick »

Having not tried it myself, I would think that the best combination would be cap -> filter -> cap -> choke -> cap. You could use a smaller second cap.

Not sure how PSD would be of use though, its a filter, but its not a inductor, so while it provides 10H ish of smoothing at 100Hz, it doesn't in any other way act like a choke.
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#59

Post by Mike H »

ed wrote:apologies if this has been asked before....cant find the description thread...

to use this in psud do we just sub a 10h choke...?..any significant resistance?
OK I just had to try to do a simulation, LOL

As Nick worked out seems equivalent to 10H into 100uF in 'standard trim'.

Using choke input (as per Rocky IV), DC = 100mA, reservoir ripple = 7V peak to peak, output ripple = 20mV peak to peak.

It's more or less a constant Voltage drop so 'DC resistance' is dependent on the DC current, the formula is:

(V-ZD1 + VG) / DC current

As designed, V-ZD1 = 20V, VG = 3V (@ 100mA out, prototype)

E.g. for 100mA, = 23V / 0.1 = 230 Ohms.

@ 200mA, 115 Ohms, and so on.

Does that help?

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#60

Post by Mike H »

If you want to simulate it in PSUD (don't see problem with that, just to get an idea) must keep the right ratio versus the filter cap, i.e. if 100uF then the 'inductance' is 10H, if 50uF, 20H, and so on like that.

But as Nick says it's not increasing the output filter cap that necessarily makes it better, it's the gate capacitor (CG) that actually controls the "smoothness" of the output. I suspect the FET merely tries to "drive" the filter cap at whatever the ripple is on its gate. It's probably powerful enough to do that.


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