Hi,
I wanted to build an easy booster pedal and figured the SHO would be the way to go.
I saw this schematic:(https://hotbottles.files.wordpress.com/2012/03/sho_mac_2.jpg)
I was able to find all that I needed except I could only get a 2N7000 instead of a BS170. I looked it up and they should do the same thing except the 2N7000's pins are the opposite direction of a BS170...
Anyways... I don't seem to get any volume boost when turning the knob. It sounds still bypassed.
What went wrong? Would a component have fried? Any help would be great!
Thanks,
LTNPD
which layout did you use? did you change anything except for the transistor? (double check the pinout).
we always like to see photos of what has been built, even if it's only still on the breadboard. and, as ever, voltages. what voltages do you have at supply, source and drain?
Hi guys,
Here are the photos:
(http://www.thamnong.com/picture/2N7000+BS170_MOSFET_N-Channel.gif)
(https://s33.postimg.org/reeqnp8cr/IMG_9437.jpg) (https://postimg.org/image/reeqnp8cr/)
(https://s33.postimg.org/6hiij2kmj/IMG_9438.jpg) (https://postimg.org/image/6hiij2kmj/)
Thanks for all the help!
LTNPD
What brand of BS170 did you use?
My notes say Fairchild, ON Semi, General, and Infineon use the DGS pinout like your illustration.
Vishay, Zotex, and Siliconex use a SGD pinout.
Don't remember where I got that info, but I wrote it in my notebook so it must be true.
Edit: Nevermind! You aren't using the BS170, I read that backwards. See post below.
Oh, also, probably much more relevant, the gold bands on those two resistors need to be green, or at least yellow.
(You have 10 ohm resistors where you want 10 million ohm resistors)
You have the resistor that is supposed to go from drain to gate going from gate to gate instead. As-is, you're basically using the MOSFET as a capacitor.
Move the end that's in hole j6 to hole h7.
And, like thermionix said, make sure the 10meg resistors aren't 10ohm resistors, but since you said you're getting sound through, those are probably fine.
Quote from: highwater on December 03, 2017, 11:13:54 PM
You have the resistor that is supposed to go from drain to gate going from gate to gate instead.
Yep, I missed that.
Quotemake sure the 10meg resistors aren't 10ohm resistors
brown - black - black - gold - brown
1 - 0 - 0 (x 10
-1) [1% tolerance] = 10 ohms
I think homeslice was thrown off by the depiction in the schematic he posted.
It shows brown - black - blue - gold (10Meg, 5% tolerance).
But at a quick glance it looks a lot like brown - black - black - gold.
Thanks guys!
It does seem that I didn't see the correct colors (thanks @thermionix !). I've also moved the resistor end to h7 (thanks @highwater !)
Somehow though ... all I get is significant volume drop... would my previous mistakes caused a diode or the transistor to fry?
Your "100k" from output to ground could actually be 130ohm. Brown-black-black-orange-brown is 100k, but brown-orange-black-black-brown is 130ohm.
Quote from: ltnpd on December 05, 2017, 09:15:32 PM
It does seem that I didn't see the correct colors
The colour printing on resistors - particularly the blue metal film ones - can be somewhat "variable". I wouldn't go by what you think you see. (And the tiny 1/8W ones are even worse.) When you buy them, measure them (to double-check) and label them. A good storage scheme can help enormously.
I have no experience with MOSFETs, but from what I've read they are relatively easy to damage. Very good chance yours is toast.
----------
With resistors and color bands...there are basically two systems in use these days, 4-band and 5-band.*
4-band has been around longer, you'll frequently see it on carbon comp and carbon film resistors. The bands represent two significant digits, a multiplier, and a tolerance band.
5-band is the same but with three significant digits. More commonly seen on the blue metal film resistors, like those on your breadboard.
* It may be more proper to say 3-band and 4-band, not counting the tolerance bands, but that's not really important.
Back in the day, resistors were most commonly available in 20%, 10%, and 5% tolerances. 20% would have no tolerance band at all, 3 bands total. 10% had a silver band, and 5% had a gold band. Most you see are either 10% or 5%, so they have a silver or gold band on one end, which makes it really easy to know which way to read the bands, because there is no significant digit associated with either silver or gold.
But now 1% tolerance resistors are quite common. A brown band is used at the end to denote 1%, which leads to some confusion, because brown is also the band color for the significant digit 1.
So the best bet, as Bluebunny says, is to read them with an ohmmeter, and remove all doubt. You may even find an occasional one that is marked incorrectly, or just plain bad, so always a good idea to check anyway.