DIYstompboxes.com

DIY Stompboxes => Building your own stompbox => Topic started by: 2x6L6 on February 11, 2006, 11:44:10 PM

Title: A bit more assistance on AMZ Mosfet Boost? switch 'pop' & debug
Post by: 2x6L6 on February 11, 2006, 11:44:10 PM
I'm back - and thanks so much for all the input so far. I have two issues - a dead  pedal (immediately below) and a loud pop when switched on.
I went throught the "What to do when it doesn't work" thread and here are the measurements and data:
1. Pedal bypasses signal fine, but produces no signal when stomped on. LED works; pedal 'pops' when stomped on and off. [I have built 2 others of the same circuit that work (except for the pop I can't get rid of!).] This 'dead' one - the bias point (R4) = 9.5 vdc, and does not change bias voltage when I add a trim pot or even remove R2, the bias resistor - this is telling me something obvious but I am having trouble grasping it.
2. AMZ Mosfet Boost
3. Built with Jack's boards and parts from SBE
4. No mods.
5. No substitutions.
6. No PNP/NPN conversion.
7. Battery voltage: 9.51
- Red battery lead at circuit board (red goes to the DC jack = 9.51vdc); the '+9v' lug on the board = 9.51 vdc
- Black battery lead at circuit board (black goes to the input jack ring = 0 vdc); the 'out' lug on the board = 8.31 vdc

Q1 (BS170)
D= 9.52
S= 8.95
G= 9.50

Z1
A= 8.92
K= 9.46
I suspect the Zener, but am not sure why? I don't have a spare 9.1v - too far to Anchorage these days. I do have a 12v and 5.xv I got from the Shack.
-------------------------
Now, regarding the pop - (the two working pedals only pop when kicked on, BTW) again, I have attempted to research this on the forum here and gleaned a few ideas but no definitive solution. I have tried:
- 1 meg resistors from tip to sleeve on both jacks - no help
- 10 meg resistors from tip to sleeve on both jacks - no help
- (1) 10 meg resistor from board input pad to sleeve of input jack - that seemed to eliminate the pop unless you stomp it back on right away, --- getting closer!
- I then tried (1) 1 meg from board input pad to sleeve of input jack, thinking the 10 meg was too slow to drain, and it seemed to work perfectly until I turned the amp up, then didn't really seem to work at all ------- in fact seems to pop when kicked off now as well, so I suppose I knocked it out of whack. This is almost a solution... but not quite.
I am not sure where to go next - a 2.2 meg (?), or back to the 10 (never tried the 10 with a loud amp...) I do really like this pedal but have to solve the pop issue!

Any help on: A) the dead pedal, and B) the 'pop' is of course graciously appreciated.
Thanks.....