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Boss_8
Copper Member
USA
44 Posts |
 Posted - 02/20/2010 : 01:47:29
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Thanks to ranjan and Dr. Bob the CE-2 clone now works. I hooked up the battery with schematic in hand and started to check all the points where voltage should be. I found two points with no voltage that originated where the pcb was circled with the black marker (see pic). There was voltage all along the trace until that point. I shined a bright lite through the pcb and could see a hair line crack all along the edge of the solder join on the pad for Q1 (transistor). I soldered a jumper from the last pad with voltage to the one with the cracked trace. I also turned around the reversed polarized cap and voila! The pedal now works! I had to adjust the trim pot for any effect type sound to come out of the pedal. Does anybody know the procedure for adjusting the pot to the proper place or is it adjust to taste?
Thanks again for your help.
Cheers,
Doug
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Edited by - Boss_8 on 02/20/2010 02:01:05 |
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ranjam
Bronze Member
Canada
82 Posts |
Posted - 02/20/2010 : 03:24:36
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| That trim pot sets the bias for one chip and the two LFO transistors. I doubt it will sound different if it is off a smidgen either way. To me it should work or not work. I know I have an MXR phase 90 that the trim pot is so touchy; if you think of the pot as going from '0' to '10' just as if it had a numbered knob on it, the phase only works with the pot at exactly 6.5 or something equally as difficult to set on a tiny control. It took me a long time to dial it in. I would just nudge past that sweet spot, and then spend more time almost staring at the pot and willing it to nudge back. But if you can get it to oscilate, I'd leave it alone. I haven't found any official Boss instruction on how to set the bias in a CE-2 yet. Not even the tonepad site tells you. I guess you have to buy the kit to find out! |
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Boss_8
Copper Member
USA
44 Posts |
Posted - 02/20/2010 : 15:30:09
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quote:
Originally posted by ranjam
That trim pot sets the bias for one chip and the two LFO transistors. I doubt it will sound different if it is off a smidgen either way. To me it should work or not work. I know I have an MXR phase 90 that the trim pot is so touchy; if you think of the pot as going from '0' to '10' just as if it had a numbered knob on it, the phase only works with the pot at exactly 6.5 or something equally as difficult to set on a tiny control. It took me a long time to dial it in. I would just nudge past that sweet spot, and then spend more time almost staring at the pot and willing it to nudge back. But if you can get it to oscilate, I'd leave it alone. I haven't found any official Boss instruction on how to set the bias in a CE-2 yet. Not even the tonepad site tells you. I guess you have to buy the kit to find out!
Ranjam,
I guess there is a way to adjust the trim pot, Laurie has a link to it on his site:
http://members.shaw.ca/lauriepedals/CE2trimpot
He also has a link to the offical Boss technotes that show the proper wave forms on an "O"-scope. I don't have an O-scope so I'll probably just adjust to taste at this point.
Cheers |
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ranjam
Bronze Member
Canada
82 Posts |
Posted - 02/20/2010 : 15:49:32
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I wouldn't have thought this, but the instructions are basically telling you to set the bias so the waveform isn't clipping. Unless I am reading it really wrong. So there is more than a sweet spot, and you shouldn't want a clipping, distorted chorus signal. You could probably also use a good DVM and set the Q point of that transistor. Probably exactly half (or as close as a teeny trim pot will allow) of the supply voltage. That should put the Q point right in the most linear part of the load line. Then you know Vce and Ic aren't saturated. But then again I could be 100% completely out to lunch.  |
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Boss_8
Copper Member
USA
44 Posts |
Posted - 02/20/2010 : 15:55:44
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quote:
Originally posted by ranjam
I wouldn't have thought this, but the instructions are basically telling you to set the bias so the waveform isn't clipping. Unless I am reading it really wrong. So there is more than a sweet spot, and you shouldn't want a clipping, distorted chorus signal. You could probably also use a good DVM and set the Q point of that transistor. Probably exactly half (or as close as a teeny trim pot will allow) of the supply voltage. That should put the Q point right in the most linear part of the load line. Then you know Vce and Ic aren't saturated. But then again I could be 100% completely out to lunch.
I'll take a look at the voltage coming out of the trim pot to see what the voltage swing is when it is making an effect tone. Thanks for the tip?
Does Laurie want to chime in on this? |
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Tonepad CE-2 troubleshooting update
