Millenium 2 bypass led not working

[Perrow]

For some reason I can't get this millenium 2 led to light up, hopefully someone can spot an error.



Red for 9V+, blue for ground, and green pad for the control connection.

Had it sort of working with a 3mm led, but it was too dim, reduced the led resistor, but then it wouldn't turn off completely, just dim a little. Couldn't get 5mm leds to light up, even with the 3904 removed. Tried different leds, 4148 J201 and 3904. Verified with my meter that the 4148 actually leak (~900M resistance measured  ).

[deadastronaut]

is it the base/emitter of the 3904 connected on the diagram...is that right?...

[Perrow]

is it the base/emitter of the 3904 connected on the diagram...is that right?...

I have checked the pinout more than once, I can check it again, but I'm reasonably sure I've got it right. Anyway, without the 3904 it should work (light up), and it doesn't.

[mr_deadmaxxx]

the one on the schematic is a MOSFET.

[deadastronaut]

^ yep..

http://www.aronnelson.com/gallery/main.php/v/diyuser/Sundgist/Millenium+2+Stripboard.gif.html

any help?..

[Perrow]

the one on the schematic is a MOSFET.

Lots of people report good result using J201s for the FET, though when looking at this page and the datasheets for J201 and MPF102 I think I should try the MPF102 in that spot.

is it the base/emitter of the 3904 connected on the diagram...is that right?...

Only the collector and base is connected in my layout and from what I can tell it is how it should be. The pinout for 2N3904 is EBC.

^ yep..

http://www.aronnelson.com/gallery/main.php/v/diyuser/Sundgist/Millenium+2+Stripboard.gif.html

any help?..

Yes, but as noted to D'Astro and in the link, J201 and MPF102 should work but with not much forward current (little or no led resistor if I understand it correctly).

I'll try and report back.

[mr_deadmaxxx]

been using this one. simple circuit.

adjust 1.5K resistor for LED current/brightness (depends on LED)
adjust 2K so that LED totally shuts down when Control is connected to ground (decreased value results in a dim light; increased value shuts down LED completely; depends on LED)

[deadastronaut]

^thats a cool little option..

[merlinb]

Lots of people report good result using J201s for the FET,

FETs have very wide tolerance. For ideal operation you want the Vgs(off) rating to be much less than the LED forward voltage, and some J201s will barely manage that with a standard red/yellow/green LED.
You could try subbing a a blue or super bright LED (high forward voltage), or try different J201s, or use a MOSFET (which is guarenteed to work).

been using this one. simple circuit.

Your 1n4148 is backwards!

[Perrow]

FETs have very wide tolerance. For ideal operation you want the Vgs(off) rating to be much less than the LED forward voltage, and some J201s will barely manage that with a standard red/yellow/green LED.
You could try subbing a a blue or super bright LED (high forward voltage), or try different J201s, or use a MOSFET (which is guarenteed to work).

Guess I'll have to breadboard this one and select components. Don't have any MOSFETs at hand (will order) so until they arrive I'll experiment with the JFETs I do have.

[mr_deadmaxxx]

Your 1n4148 is backwards!

not really. i use this configuration with DSG Fets like J201 or 2N5486.
I only reverse 1N4148 when I use DGS Fets like 2N3819.
1n4148 cathode is always on V+.

[Earthscum]

Don -  From your schem, the way I see it working is that you are using the Jfet as a diode... Control goes high, gate goes high, Jfet works like a jfet. Control goes low, looks like it works as a shunt, no control voltage, should just work like putting V+ through a diode before it goes to the LED Anode.

[merlinb]

Ah sorry, I assumed the upper line was V+. Didn't look closely!

[mr_deadmaxxx]

that is actually RG's Millenium Bypass 1.

http://www.geofex.com/article_folders/millenium/millen.htm

[Earthscum]

Perrow... on your layout, the jfet's Drain and Source are reversed. If you drop a MPF102 in there, it may not turn off all the way (some take near 4.5V to turn off... I love them to death, but tolerances suck... wish they would've batched them like Japanese). The MPF would, however, work in reverse, if you can get it to pull off completely. I really don't know how well that J201 is working with D and S reversed.

Personally, my absolute favorite for Mill bypass is the 2SK117GR from Tayda. Very low Vgs off and higher IDSS ( like the gate of a J201 with the channel resistance of a 2N5457).

[mr_deadmaxxx]

As for me, 2N3819, 2N5484, 2N5485 and 5486.

[frank_p]

If I remember well I had trouble with a millenium II:  Not all mosfets will work optimally in the circuit.  I had to get back to the 2n7000 in my case.

There are also these other options:
http://www.geofex.com/Article_Folders/Millenium/The%20Next%20Millenium.pdf

[Perrow]

I thought S was supposed to be on the positive side and D closer to ground, or? J201 being DSG and the middle pin being the positive I was positively sure I nailed that part. It should be the other way?

[frank_p]

I thought S was supposed to be on the positive side and D closer to ground, or? J201 being DSG and the middle pin being the positive I was positively sure I nailed that part. It should be the other way?

Drain to positive, gate to switch, source to LED.

[Perrow]

I had to get back to the 2n7000 in my case.

Those are 8 cents each from Tayda, I'll see if I can save up to buy a few