MILL BYPASS 2 on DOD308

[Davide]

I'm a little confused...  :oops:
i've built a Dod 308 malmsteen overdrive clone, using the GeneralGuitarGadgets layout of the dod 250 (with a little PCB mod, using a 4558 ic..).  It works great.
I've a DPDT switch so i was going to add the millennium bypass 2 circuit... i've finished the circuit but i've read many things about pulldown resistors to prevent pops... without understaing if i really need them...
so ...

1) pulldown resistors : where and how many ohms ?

2) lookin' at the DPDT wiring using a MillBypass 2 i dont see the Ground connection... so .. i dont need it ?


Thank you !!!

Davide

[R.G.]

1) pulldown resistors : where and how many ohms ?

Read the info on GEO. You need pulldowns on the outboard side of input and output caps on your effect, always. 100K (marginal) up to 1M (preferable).

2) lookin' at the DPDT wiring using a MillBypass 2 i dont see the Ground connection... so .. i dont need it ?

The DPDT wiring may not need a ground connection, but the Millenium 2 needs a ground, or no current will flow. Read the info on GEO about the Millenium 2 bypass.

[Davide]

Houston... we got a problem  :cry:


i've made the Millenium Bypass 2 following this scheme
http://www.geofex.com/Article_Folders/Millenium/mill2bd.gif

the diodes i've used are :  1N4148 and 1N4007

i've used a BS170 mosfet....

now... source gate and drain are in the right places...

but i have no light at all :/

i dont know if the problem is the mosfet... or the dpdt contact... everything seems ok...

(i dont know if this could be useful... if i short drain and gate i have a weak light... obviously i have the regular light if i short source and drain..)

help

[Davide]

i've tried another BS170..... same results...  :cry:
nothing seems to work...

(inverting the mosfet contacts the light stays always on as it should do...)

[loki]

I'm trying to guess here....
could it be that the problem is the 1N4007 diode?
the schematic for the mill 2 bypass says it should be a "low leakage diode" i've made a search with google (i'm thinking of building the mill bypass 2 too, and didn't know what are low leakage diodes) and found diodes like 1N456, 1N457, 1N459 as "low leakage"
maybe that's the prob... but i don't know for sure

[Davide]

mmm probably... i dont know.. in my schematic it says "any silicon diode"...
the diode i've used is a general purpose rectifier.. ( 1 ampere i think )..

[audioguy]

The digram located http://www.geofex.com/Article_Folders/Millenium/mill2bd.gif is a good looking picture, however it is a bit vague for us beginers when it says things like 'low leakage diode' or 'current limiting resistor' Is there a definitive parts list of what comprises the best configuration?

Audioguy

Please be gentle, I'm still new

[Davide]

This is my "not working" version ...

[R.G.]

The simplest low leakage diode is the collector-base junction of an ordinary NPN bipolar transistor. I strongly recommend using one of these.

I guess I need to rewrite that stuff. It seems like every new person making one of these manages to find a new way to fet a non-low leakage diode.

Davide: change out the 1N4007 for the collector-base of an NPN transistor. For an NPN transistor like the 2N3904, use the collector for the cathode/bar of the diode and the base for the anode/arrow of the diode.

Audioguy: There is no one best list of components. This thing is so simple that it can be built out of almost any batch of parts that has a suitable MOSFET and 1N4148. The "current limiting resistor" is that 4.7K resistor in series with the LED. When the MOSFET switches on, it's the only thing that limits current through the LED. Making that bigger limits the LED current more and makes the LED dimmer. Smaller values make the LED brighter. The MOSFET can be BS170, 2N7000, or one of many others. They all work equally well, so use what you can find. A CMOS chip is even simpler to use.

The gate-channel of any JFET makes a good low leakage diode as well.

This thing is the antithesis of the other beginner's bain - the circuit that is hypersensitive to just the right part that is only available on special order from a supplier with a six month lead time.

[audioguy]

R.G- thanks for the info.. most helpful my friend!


A.G.

[Davide]

ok ! i'm going tryin' it as soon as i can

thank you !!

(ant thank you for the patience... :roll: )

ciao  :wink:

[audioguy]

I just built a mill BP2 and Im getting a solid light. I didnt hook it up to any effect, just the bypass circuit and the dpdt. Does it need to have everything else hooked up to work correctly? That doesnt make much sense, but Im grasping here...
It looks exactly like the diagram, using an NTE519, NTE177 for the diodes, and an NTE490 for my mosfet.
I plugged the battery straight in, hooked up the DPDT and I get a solid light


HELP!!!

[Davide]

What do you mean for "solid" light ?
It's always on ?  If so it's probably a wrong orientation of the mosfet's pins... look at the datasheet..

sorry if i misunderstood

[audioguy]

always on- checked it, and it looks good. turned it around just in case, and no change.

[R.G.]

Does it remain on when the MOSFET is removed entirely?

[audioguy]

I havn't tried to removing it and testing.
However I think I might have just figured out all of my trouble. Im using the Xwing type DPDT, and I might have it all alligned incorrectly. I just stumbled across a diagram that shows the wiring a little differently than I have it done. In the past I was using the Carling switch shown on most diagrams and PCB layouts. I wasn't having any problems until I got cheap and bought the less expensive Xwings... Live and learn.
When I get home this eve I'll test that theory.

Thanks for your help!