Just built up a Serendipity and it's not giving me any love. I get signal in bypass, signal when it's switched on, LED works, but no drive. The drive control acts like a volume control. The volume control also acts like a volume control. The voice pot seems to be working properly, and it's hard to tell if the tone knob is doing anything.
I did sub a TL072 instead of the AD712. So far the only thing I've tried is switching the transistors around in case I had the pinout backwards. No change when I switched them, though.
I'll go through and double check my resistor values tonight. I probably should check to make sure I don't have the pots mixed up, too.
Any other suggestions?
did you use 2n700's or some other fet? I had a stubborn vero build of this circuit with similar behavior. it was a problem with the fets. I replaced them and it was fine. bs 170's work great in that circuit too.
What brand of 2n7000 are they?
mine where cheap ones from tayda. I bought a bag of 100 and I've had a few duds
It's a bit of a pain slimtriggers, but socket the two transistors and try putting in some diodes there like 1n914. If you get distortion then it's a matter of either different pinouts or perhaps bum transistors.
Yeah mine are from Tayda as well. I socketed the transistors, so swapping them with diodes will only be a minor inconvenience. I'll give that a shot.
I'll let you know how it goes 8)
I tried 1n4148's in place of the transistors, but no change. I tried 2 more transistors (off the same strip, though) but no change there either.
All the resistors check out, and my pots are correct. Maybe I'll try a 4558 just in case...
hmm... it's almost like there is a short somewhere in the neg feedback loop of IC1A. A solder bridge perhaps?
This is a weird one.
Tried a 4558, but no change. Would an IRF510 work if I could finagle the leads appropriately? That might be a tough one to try out, though. I only have 1 BS170, but I may switch it into both spots to see if there's any change. BS170 has pinout opposite of a 2n7000 if I understand correctly.
I would take some pics, but I haven't seen my camera since we went to Gettysburg a few weeks ago :(
Can you post hi res pics of both the component and solder sides inclusive of the wiring?
Voltages on the IC are in order, as well.
No way to take a pic right now, but here are the voltages.
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Volts at the transistors:
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OK. Found the camera :)
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Good Lord the soldering looks ugly all blown up :P I already see a couple of spots that may be suspicious.
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Never got it figured out. So, I etched my own from Madbean's layout and started from scratch. Works great! I think this is my new favorite drive 8)
Man, that insulation on the Smallbear wire really shrinks up when you solder it. I think I'm going to try out the "Barry's Best" wire and see if it's any better.
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That's the way to do it. Great job!
great job. I might have to do the same thing with my neutrino.
Did you use the parts from the old pcb or start with new board and new parts?
Quote from: snz728 on August 04, 2011, 12:26:27 AM
great job. I might have to do the same thing with my neutrino.
Did you use the parts from the old pcb or start with new board and new parts?
Caps, resistors and sockets were all new. I used the same transistors, IC and off board components. Since the switch and jacks were already wired up, it was really only just a matter of stuffing a new board. For me anyway, that's a whole lot faster than trying to debug the other one.
I've only ever had one board defeat me. I had a Phase 90 clone I was building, and I tried for a looooong time to get it to work. I finally got a new board and it fired up immediately. SO frustrating, but glad it's working for you.
Like the crazy enclosure too.
Jacob
The only one that has defeated me so far has been a CE-2 clone! Those damn modulation effects.
I had the same issue, built 3 different Serendipity boards from the etching layout. Got volume, tone control, but the drive was very weak. I kept scratching my head and finally came back to the layout. Turns out I goofed with the C2 capacitor from incorrectly converting it to uF. I was using a .47 or something when I should have been using a .0001 uF. Check your cap values - they are easy to screw up is my advice. I hope this post helps someone in the future with a similiar issue.
Now I have like 3 or 4+ Serendipitys...guess I will have to give some to friends :)