Millenium bypass not working.

[jpm83]

My problem is that led just won´t liht up. I used a vero layout from layouts gallery. Can you leave that low leagage diode off as I did because the layout said it is optional and if not which diode I can use in that place. I have also made the connection thru resistor to the ground from switch.

Thanks for answering and merry christmas for all of you.

[bioroids]

Hi!

You can't ommit the diode. A simple 1N4148 will work fine (ate least it always works on mine)

Luck

Miguel

[jpm83]

Thanks.
I just have to try now figure out what I have missed in debugging process. If you (anyone) have experiences whitch are normal or abnormal things that can cause this every help is welcome.

[bioroids]

Oh I thought you had ommited the diode.

Are you sure the wiring is ok and the transistors and led are oriented correctly?
Wich version of the Millenuim are you using?

Miguel

[jpm83]

I´m using millenium bypass2. I changed the diode around and when I tested it tranny melted. I have a picture here if that helps for figuring out whats going on.
http://img336.imageshack.us/my.php?image=milleniumbypass5uh.jpg

[bioroids]

The 1N914 diode has to have it's negative (i.e. the side marked with a line) to the +9v, otherwise the bypass will not work (aparently burning the transistor). I dont know exactly what the other diode does, but i never ommited it.

Mosfets can be tricky, they burn easily with the soldering heat and/or static discharge, so you have to be very carefull with that. I sometimes have to unplug the soldering iron from the wall power prior to soldering just because of that!

Luck

Miguel

[jpm83]

Thanks.
Was everything otherwise OK in the picture.

[bioroids]

My monitor is too dark (burned phosphor I think) to see well. I can't really see the transistor.

The led seems to be backwards looking closely, are you sure the flat side is the one connected to the resistor? The long lead has to go to the positive supply.

Luck

Miguel

[bioroids]

Hey, what value is that resistor by the way?

[jpm83]

Resistor is 390 ohm. I just ordered new fet, I hope I recieve them by weekend.The round side of FET is facing to the wires and flat of LED is in 9 volt+.  And really thanks for all the help

[bioroids]

I think you got the led backwards, you need the round side pointing and connected to +9v (the same place where you connect the line side of the 1N914 diode.

Also, the resistor is a little too low, if you use high brigthness leds you can try something in the 2k2-10k range better. It will draw less current and the led will be perfectly bright.

What mosfet are you using?

Luck 

Miguel

[jpm83]

I´m using BS170 and diode is 1N4148, I couldn´t find 1N914 anywhere here in Finland.

[bioroids]

It is fine, both components should work ok.

Luck

Miguel

[Bernardduur]

Weird.... I'm always using 1N4148's and all worked....

Maybe try the C version of the millenium bypass. Never failed me

[jpm83]

By the way is this layout correct, I´m making it from this.
http://aronnelson.com/gallery/TheBigMan-Layouts/MB2N

[R.G.]

Can you leave that low leagage diode off as I did because the layout said it is optional and if not which diode I can use in that place

Yes, you can. The low leakage diode is optional. It protects the MOSFET gate against the rare occurence of you killing the gate with static electricity while changing the battery under low humidity conditions.

The HIGH leakage diode, the one from +9 to the gate of the MOSFET is critical and cannot be omitted. Both 1N914 and 1N4148 work, although some newer vintage versions of these are not higher leakage any more. You can parallel several of them to get more leakage.

If you (anyone) have experiences whitch are normal or abnormal things that can cause this every help is welcome.

Probably 9 out of 10 of the problems people have with this is the pinout on the MOSFET. MOSFET pinouts vary. Look up the datasheet for the manufacturer of YOUR particular MOSFET. If you put yourself in a high humidity environment (that is, a steamy bathroom with the shower running hot to guarantee no static electricity)  you can find the pinout by finding which two pins conduct like a diode. That is the reverse conduction body diode, and in an N channel MOSFET, the cathode of that diode is the drain pin and the anode is the source pin. The other pin is the gate. Gates only conduct when they've been destroyed.

The round side of FET is facing to the wires and flat of LED is in 9 volt+.

As bio says, that's probably backwards. Check the direction your LED conducts by hooking it up to a battery through a resistor.

It's likely that there's a pinout or connection problem.

[TheBigMan]

The layout is definitely correct, I have used it several times.  The LEDs cathode is denoted by the flat side normally, and that side should be connected to ground, which happens through the MOSFET in this case.