LED problem with Millenium 2

[bancika]

Hi,
I just put Millenium 2 board (made from vero layout found here) with 1N914 diode and BS170 FET (no optional diode) but LED won't light. Other than that it works ok.
It's connected like this:

1 2 3
4 5 6

1 to 6
2 from input
3 to FX
4 to mill2
5 from FX
6 to output

and FX is nurse quacky.
Any ideas?

[R.G.]

I have not looked at the nurse quacky schemo, but you can test your Mill 2.

The Millenium 2 is a resistance-to-ground detector. You can test it by hooking up DC power to the Mill 2 circuit, and then alternately connecting/disconnecting the control line to a 1M or lower resistance to ground. If the LED comes on when the control line is open and goes off when the control line is touched to the resistor, then the Mill 2 is working correctly. Get the mill 2 working, then hook it to the effect.

The effect MUST have a DC resistance to ground at the output for the Mill 2 to work. That can be a 1M or less pull down resistor.

[bancika]

Damn, no luck with Mill, this is my second try and nothing
Is it possible that FET is bad and bypass still works?
Also, if I'm not wrong Nurse has 470K resistor to ground, so that shouldn't be the problem. I also tried separately to connect 150K resistor to ground and no luck.
By the way, here's layout, guess it's OK
http://aronnelson.com/gallery/TheBigMan-Layouts/mb

[bancika]

One more thing, here are FET voltages:
D: 9V
G: 0
S: 0

[R.G.]

Is it possible that FET is bad and bypass still works?

Yes, it is 100% possible that the Millenium MOSFET is bad and the bypass still works. The Millenium bypass has almost nothing to do with the bypass portion - all it does is indicate when the switching hooks its control line to ground.

I also tried separately to connect 150K resistor to ground and no luck.

So it looks like the Millenium circuit is not working.

By the way, here's layout, guess it's OK
http://aronnelson.com/gallery/TheBigMan-Layouts/mb

Which one of the four did you try, and with which FET? It makes a big difference.

[bancika]

It's NPN version with BS170 FET and without optional diode. Can MPF102 work here, I have only this here to try instead of BS170
Tnx

[R.G.]

It's NPN version with BS170 FET and without optional diode. Can MPF102 work here, I have only this here to try instead of BS170

OK. I'm interpreting that as you saying:

"It is the N-channel version intended to be used with the BS170 MOSFET and without the optional diode." (I marked the relevant points in bold.)
If that is not a correct interpretation, please correct me.

There are two versions because there are two major kinds of FETS, Junction FETS (JFETs) and Metal Oxide Semiconductor FETs, or MOSFETs. They are fundamentally different in how they work. MPF102 is a JFET, and BS170 is a MOSFET.

An MPF102 will not work in a circuit intended for the MOSFET BS170. A selected MPF102 might work in the Millenium 1 version but might not too. This is because the MPF102 has a higher gate voltage required to turn it off than some other JFETs. If you got lucky and got an especially low Vgs version of the MPF102, it might work in the Millenium 1. But many of them will not.

Wherer the layout says "N-channel or P-channel FET as appropriate" it should "JFET as appropriate", and ideally would mention several of the low Vgs ones like the 2N5292, the 2N5484/85 and some others.

If I have interpreted your note correctly, your available FET may or may not be able to work properly in this circuit.