Random Number Generator sadness

Started by patrickcurran21, June 28, 2011, 03:39:56 PM

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patrickcurran21

A couple days ago I built a random number generator using this layout

I couldn't get vero so I built it on pad per hole.  This was my first pedal build so I can't say I really expected it to work the first time around.  Anyways here are the symptoms... when the effect is engaged either no sound gets through or if I hit the strings pretty hard I'll get a signal, but it has not been affected other than being a bit quieter than in bypass mode.  My LED does turn on.  I wired the pedal without a battery snap and it's running off a wall wart that's putting out just under 9 volts, 8.85V at the moment.  I also used mostly 1/8 watt resistors in the build since that's what I had laying around.  I'm not sure if that affects anything but I'm trying to supply as much information as I can.  The transistor voltages are as follows
Q1 C-7.4V B-6.45V E-0V
Q2 C-8.28V B-7.85V E-0V
Q3 C-8.19V B-8.14V E-0V
Q4 C-8.52 V B-8.18V E-0V
these are nowhere near the voltages people were getting in this thread http://www.diystompboxes.com/smfforum/index.php?topic=87112.0
so something is very wrong... but since I am new to this I'm not seeing what it is... it may be obvious to some of you what the problem is though... can't wait to get this thing running.. any and all help is appreciated  :)

defaced

Can you get a pic of the top and bottom of your board?  If a layout is verified, I usually think the error was made between the chair and the soldering iron.  Not that I have any experience with that or anything.    ;)
-Mike

patrickcurran21

#2

those blobs of solder on some of the component leads are from extending them

you can see where the power + lead is on the lower left of the image, right above that is the input.. ground is along the top edge of the image. pretty messy >.<... methinks i need to find something better than heat to strip wires
and now a few closer images of the top of the board, starting with the left side

in the meantime I'm gonna go back over this thing with a magnifying glass looking for solder bridges
edit: when the effect is on, I no longer have to hit the strings hard to get a signal to come through, one of the transistors was loose in the socket so i fixed that.  the signal is still quieter than in bypass mode and is unchanged

Morocotopo

For the connections on the underside of the board, I would´t use wires, it´s better to use the part´s "legs" to connect from one point to another, or a bit of "leg" if the parts don´t reach each other. The wire´s insulation melts, can prevent a good connection, is messy... Looks to me that a rebuild would be a good idea, to make it cleaner. Less chance of a bad connection. Also,don´t use your solder gun to melt plastic, it ruins the tip. Also, don´t bend the legs of the parts, especially the ceramic caps (orange ones) so close to the body, you might break them internally.
Morocotopo

patrickcurran21

alrighty, thanks for the insight. I shall do a rebuild today and see what happens!

patrickcurran21

Well I did a rebuild yesterday, a couple of the cap values had drifted enough to swap them... mighta toasted them a bit last time around  :icon_redface: ... so i replaced those.  Same problem... but a little different.  No effect when device is engaged.  It is almost at unity when the volume is all the way up.  Something interesting though, I replaced the feedback resistor with a 100k pot (described in this thread  http://www.diystompboxes.com/smfforum/index.php?topic=50491.0) and... if i'm reading my meter right, when the pot is all the way up (100K, the original resistor value) even when I hit the strings very hard it's splattery? sounding and the signal can't get through, but then when the pot is open all the way, the volume of playing before sound gets through is pretty quiet and most everything gets through unless i am playing very softly.  New transistor voltages are as follows:
Q1 C-7.36 B-6.49 E-0
Q2 C-7.66 B-7.22 E-0
Q3 C-7.40 B-7.32 E-0
Q4 C-7.72 B-7.40 E-0
The voltages are moving in the right direction but are still very far off from what they should be.  Also, something strange happened when I was measuring Q2.  When I touched my probe to the base the voltage started going down, I checked the collector and it was also going down with the base.  This only happened when I touched the probe to the base of that transistor. 
This is my third rebuild of this pedal so I'm beginning to wonder if the problem could possibly be offboard?  Does anyone know of any offboard issues that could explain these symptoms?  I will upload a picture of the top and bottom of the new board shortly...


patrickcurran21

#7
turns out the wall wart i was testing with was center positive  :icon_redface: I didn't even think to check that, anyways soundclips!!! be gentle, and sorry about the repeated riffage! there's four clips, on 2 and 4 i removed the pot that replaced the feedback resisitor, which just turned the thing into a really sick sounding (literally and figuratively) fuzz... anyways enjoy