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DIYstompboxes.com  |  Projects  |  Beginner Project  |  Newbie needs debug assistance! 0 Members and 1 Guest are viewing this topic. « previous next »
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Author Topic: Newbie needs debug assistance!  (Read 3228 times)
Mikate
Posts: 7

Aaron Mikate Vancouver, BC


Newbie needs debug assistance!
« on: June 11, 2007, 03:31:42 PM »

Hey there folks.  I'd like to thank Aron and everyone else for all the help this forum has been to me in building my first ever pedal.  BUT - the damn thing don't work.  So I toss my cry of "Help" into cyberspace...

Here's the deal:
1. Built it once, screwed up the schematic (I was building from the top) tried to remedy, didn't work at all.
2. Built it again, paid closer attention to my soldering.  When I use it, I get an extreme volume cut, barely audible at lower settings, last 10% of the pot gives low-volume, highly distorted output.
3. Followed the walkthru to a T, except switched transistor with an NTE123AP.  Stereo in, mono out, 5k linear pot, etc.
4. Checked voltages, and compared with the schematic/voltage thing offered in the thread "Another non-working NPN boost".

Like so:


(Analog multi-meter = one decimal point only  Wink )The base looks low, as does the collector, but I'm not sure what to do about it.  Also: voltage at circuit board end of BLACK battery lead is nonexistent (0.0) - is this right?  Triple-checked my resistor/capacitor values, and they're all good.  Transistor's facing the right way.  Couldn't find any solder bridges - though my soldering is pretty ugly.  I'll post some pictures once I get my hands on a camera, so you can all wince at my handiwork.

Thanks loads.  I can't wait to get this thing working!
Aaron
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"i was looking at a moment imploding upon itself, a sealed room, closed circuit.  that is how i recall LA."  -Lee Ranaldo
Mikate
Posts: 7

Aaron Mikate Vancouver, BC


Re: Newbie needs debug assistance!
« Reply #1 on: June 11, 2007, 04:41:03 PM »

Here's a shot.

note the red-circled solder "spills".  They don't seem to be making a short . . . is it still a problem otherwise?

Aaron
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"i was looking at a moment imploding upon itself, a sealed room, closed circuit.  that is how i recall LA."  -Lee Ranaldo
ubersam
Posts: 366


Sam B. - Los Angeles, CA


Re: Newbie needs debug assistance!
« Reply #2 on: June 12, 2007, 01:46:09 PM »

Double check the pin orientation of the transistors. The NTE123AP's pinout, with the flat side facing you and the pins pointing down: pins from left to right are: Emitter - Base - Collector.

Also, it would not hurt to clean up the solder blobs, even if it does not look like its shorting anything out.
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aron
Administrator
Posts: 10215

Aron Nelson


Re: Newbie needs debug assistance!
« Reply #3 on: June 12, 2007, 02:50:12 PM »

Trust your meter. Test the solder connections by using the continuity check on the meter.
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Mikate
Posts: 7

Aaron Mikate Vancouver, BC


Re: Newbie needs debug assistance!
« Reply #4 on: June 12, 2007, 10:15:01 PM »

Okay.  Thanks for the tips, guys.  I verified my transistor orientation and it's plugged into the socket right.  Tested for continuity, and as far as shorts go, the wiring seems okay.  But I did come up with some interesting (though possibly unhelpful) numbers:

Running just off the empty socket, no battery or input/output cables:
22uf cap = 50k
10uf cap = 250k
between base and collector = 100k
base and emitter = 60k
collector and emitter = 150k

The ohms found between the socket pins seem to check out, as resistance adds up to 60k btwn B+C, for instance, adding up the resistor and 22uf cap between the pins; same goes for the other pins (just a little beginner's diagnosis  Smiley )

When I plugged in the transistor, I came up with these changes in values:
22uf cap = 18k
10uf cap = 180k
base and emitter = 12k
47k resistor = 20k (??)
100k resistor to 9v = 26k (??)

Again, I don't know if these numbers mean anything, or rather have any bearing on my problem, or if that's just what happens when you run a circuit, or what.  But I'd sure like to know!

Thanks
Aaron
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"i was looking at a moment imploding upon itself, a sealed room, closed circuit.  that is how i recall LA."  -Lee Ranaldo
aron
Administrator
Posts: 10215

Aron Nelson


Re: Newbie needs debug assistance!
« Reply #5 on: June 12, 2007, 11:19:00 PM »

Set your meter to volts (DC) and then give use the voltages on each pin of the transistor. Put the black probe on ground and touch each pin with the red and write down the voltages.
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Mikate
Posts: 7

Aaron Mikate Vancouver, BC


Re: Newbie needs debug assistance!
« Reply #6 on: June 13, 2007, 01:08:02 AM »

Got 'em.  Actually I posted the voltages on the schematic at the top of the thread, but here they are again.

C = 4.7
B = 2.1
E = 2.3
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"i was looking at a moment imploding upon itself, a sealed room, closed circuit.  that is how i recall LA."  -Lee Ranaldo
aron
Administrator
Posts: 10215

Aron Nelson


Re: Newbie needs debug assistance!
« Reply #7 on: June 13, 2007, 02:32:52 AM »

On the row (left to right) of the word Bus, on the u of Bus, you have a red circle, how is that solder joint connecting to the emitter of the transistor?
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Mikate
Posts: 7

Aaron Mikate Vancouver, BC


Re: Newbie needs debug assistance!
« Reply #8 on: June 13, 2007, 01:10:56 PM »

That joint is just a solder spill.  I checked for continuity and it doesn't connect.  Neither do any of the other spills I circled on the photo.
Given the tranny voltages, is it any easier to pinpoint a location that might have a short/bad component?  Or is it more like "there's gotta be a problem somewhere ??"
Thanks for your help so far Aron.  Please don't give up on me yet!
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"i was looking at a moment imploding upon itself, a sealed room, closed circuit.  that is how i recall LA."  -Lee Ranaldo
aron
Administrator
Posts: 10215

Aron Nelson


Re: Newbie needs debug assistance!
« Reply #9 on: June 13, 2007, 01:59:25 PM »

Can you take a picture of the top of the board?
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