Parentheses boost issues

swanforgetter

swanforgetter

New member
hey all,

working through a parentheses (on the big pcb) right now. i’ve got everything working except the boost...having a lot of trouble here. i have checked all component values and they’re correct. someone on reddit helped me out and gave me voltages on the BS170 pins and i think i’ve tracked my issue down (at least partially) to here but i’m out of ideas - his working pedal gets D - 4.66, G - 2.25 and S - .19. mine is getting a full 9V on the drain and nothing on G or S. reflowed joints on the socket, swapped out the transistor for another BS170 (all bought from tayda) and still no luck. i’ve attached a picture with highlighted resistors that don’t have current flow. any ideas? F44108BD-3768-416A-80DD-79D1EF9D7C7E.jpeg
 
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Chuck D. Bones said:
My guess is that either R29 is open, R30 is the wrong value, there's a short from Q6-G to ground or Q6 is blown.

BTW, it is normal for no DC current to flow in R28 because C22 blocks all DC.
Click to expand...

i’ll check those out. going to be away from my work area for the next 2 weeks while i study for finals, when i come back i plan on running through it with an audio probe if redoing R29/30 doesn’t work.
 
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Let's confirm that the DC voltages are correct or can be corrected before audio probing. Make measurements with Q6 installed and
out of the board. Is Q6 socketed? Can we get pix of the board?
 
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Sorry to piggy back on this thread, but I've got a similar thing going with my parentheses mini build. Everything is working except the boost. When engaged it cuts output way down, probably half... I checked R29 and R30, they're okay.

I'm actually not sure how to check the BS170 out, can I test it in place? Any chance there's another issue since I've got some signal but it's really low?
 
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First, visually inspect to make sure R31 & R32 are correct. If they are, then let's make sure the BS170 is biasing correctly. Measure The drain, gate and source voltages w.r.t. ground with power on and no signal. Depending on your meter, the gate voltage might read a little low, but we can work around that. Drain should be around 5V, gate should be 1/2 the drain voltage and source should be around 0.2V. If you're in the ballpark, then Q6, R29 - R32 are good. Make sure your board is clean and send us some pix.
 
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I have issues with this pedal too... One of them is that on the boost side, the BS170 drain & source seem to be short circuited. It is socketed, so I checked it out of the board too. On the board, when 9V (9,4 to be specific) are applied to the circuit I measure 9V in each BS170 leg (compared to ground). I am pretty sure that I need a new BS170. Any ideas?
 
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Not to totally resurrect a dead thread, but my Tayda BS170s all shit the bed in one day. Pedal worked fine all around until today randomly. Had the boost working, clicked it off, then back on, and all my signal cut out. Switched a new one in worked for one play through, then cut out again as soon as I hit the footswitch.

Anything I can sub in its place? I've got a couple N channel transistors of random types.
 
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Madallop said:
Not to totally resurrect a dead thread, but my Tayda BS170s all shit the bed in one day. Pedal worked fine all around until today randomly. Had the boost working, clicked it off, then back on, and all my signal cut out. Switched a new one in worked for one play through, then cut out again as soon as I hit the footswitch.

Anything I can sub in its place? I've got a couple N channel transistors of random types.
Click to expand...
Okay, so now that I've switched out another transistor, it works intermittently like it's my switch.

Sorry to resurrect this thread and hope the OP got this situation solved.
 
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So maybe it's not the BS170? I have BS170s from Tayda and DigiKey; no problems with any of them. Are you aware that MOSFET transistors are very susceptible to ESD (electro-static discharge) damage? The safe way to store them is in an ESD bag (the metallized mylar kind) or aluminum foil. When you handle them, everything needs to be grounded. You, the workbench, the soldering iron, etc. Don't assemble boards if the humidity is below 25%. I follow most of the rules. My bench is not grounded. When a MOSFET, or any semiconductor for that matter, is damaged by ESD, it might be completely dead the first time you power it up. They can also be "walking wounded." They seem to work, but may not meet spec or might die in a week or a year. So before you condemn Tayda, make sure it isn't something under your control that caused the pedal failure. ;)
 
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Chuck D. Bones said:
So maybe it's not the BS170? I have BS170s from Tayda and DigiKey; no problems with any of them. Are you aware that MOSFET transistors are very susceptible to ESD (electro-static discharge) damage? The safe way to store them is in an ESD bag (the metallized mylar kind) or aluminum foil. When you handle them, everything needs to be grounded. You, the workbench, the soldering iron, etc. Don't assemble boards if the humidity is below 25%. I follow most of the rules. My bench is not grounded. When a MOSFET, or any semiconductor for that matter, is damaged by ESD, it might be completely dead the first time you power it up. They can also be "walking wounded." They seem to work, but may not meet spec or might die in a week or a year. So before you condemn Tayda, make sure it isn't something under your control that caused the pedal failure. ;)
Click to expand...
Absolutely! Tayda has been great so far so I didn't want to throw them under the bus.

Turns out, I had a dirty switch AND multiple cold solder joints due to crappy solder (97/3 from Lowe's is just crap. Kester 60/40 is ace). Reflowed all resistors in the signal path because they would pop in and out intermittently just by touching them with a pencil eraser.

Thanks for the reply, too! Really dig the information on this forum!
 
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