DIY boost problems - does not work right away

[GibsonGM]

The diodes are over-voltage protection for the Gate. They MUST connect to Gate. (Especially if he is gonna "touch the tip a couple of times".) There should be a DOT there. (And otherwise: what are these diodes for?)

But that's not the problem. It will work without the diodes UNTIL static shocks blow-up the Gate and it stops working forever.

Can't you just use ONE diode to do the same, gate to source and rated lower than the pop voltage? Zener etc?

[duck_arse]

orman uses the zener gate-to-source, the super-hard-on uses the diode gate clamps.

[GibsonGM]

orman uses the zener gate-to-source, the super-hard-on uses the diode gate clamps.

I know, that's why I ask. I haven't seen this 2 diode configuration, and it threw me...the SHO schematics I've run across used a single Zener, not 2 diodes that way, but searching for the schem. again I now see some new variations appear to do this. 

[powerslide]

I have two questions - why not change the input cap? and why the hell are they using a 100uF output cap? if the 100k to ground following were missing, that cap might act funnee for a while, like until it charged up, or something.

I will try a new input cap ASAP.

I'll leave the second question for more seasoned members to discuss. Is that output cap a decoupling capacitor? Blocks DC but allows AC to pass through? That's as far as I'd know.

I would really like to thank everybody again for the input you share!

[powerslide]

New input cap installed, no changes.

[EBK]

Try replacing the pot with a fixed resistor, perhaps 2.2k or 2.7k (mid volume setting) and see if it works (and measure those voltages again, of course).

[EBK]

Regarding that 100uF cap....
I've seen other versions of this circuit that use a 10uF cap there instead.  Swapping that 100uF out might be worth a try.

[powerslide]

What pedal is this based on if I may ask? The site only says it is a clone of a "well known boutique boost".

Maybe I should try with another schematic

Just for fun today I threw together another one of my flagship LPB1 clones, wired it and works like a charm. Are LPBs my only destiny?

[amz-fx]

Is the drain of the mosfet connected to the junction of R3 and R4?  It looks like it is not, but hard to tell from the photos.

The LED is backwards in the schematic.

regards, Jack

[EBK]

What pedal is this based on if I may ask? The site only says it is a clone of a "well known boutique boost".

I believe it is OK to say that this is a clone of a Zvex SHO.*

Lots of good info here:
http://www.diystompboxes.com/smfforum/index.php?topic=82566.msg685169#msg685169

*See http://www.diystompboxes.com/smfforum/index.php?topic=82357.msg683239#msg683239

[powerslide]

Is the drain of the mosfet connected to the junction of R3 and R4?  It looks like it is not, but hard to tell from the photos.

The LED is backwards in the schematic.

regards, Jack

I have carefully checked it, and R3 goes up via a shorter jumper (row 1 & 2; 6th hole from right to left, top view) to R4 and adjacent to that is the second jumper that goes from row 1 to row 3 (5th hole R->L), the same row as the C2. The second jumper (slightly crimped and not straight at all) might look like the C2's leg but it is not. C2+ connects to drain and the negative goes to row 4, the same row as the gate of the transistor, but the copper track is cut between the negative lead on the C2 and the middle prong on the transistor socket.

At first it seemed to me that you are completely right on this one and took me a couple of times to check to see if I really wired it right. But when I was putting it together I didn't plan much in advance and thought one jumper would be enough, until I realized that this junction is now far away from the transistor's drain, so I had to add another jumper.

[EBK]

For what it's worth, I've traced your board from the pics and your description:

Can't get a clear view of the transistor marking though....