Author Topic: debugging  (Read 10955 times)

emstin1

debugging
« on: September 21, 2009, 08:38:54 PM »
so i built the npn boost, without the switch and LED (for now).  when i play through it, i get a real weak and real fuzzy sound that decays really quickly without much volume. i measured the voltage for the transistor pins and i got about 1 on the collector, but i don't get anything from the base.  I've been looking through the forums and haven't been able to find anything that's similar to my problem.  is it a bad solder joint?  wiring?  thanks in advance.

emstin1

Re: debugging
« Reply #1 on: September 21, 2009, 08:57:51 PM »
slight error, its a reading of 5 dcvolts

aron

Re: debugging
« Reply #2 on: September 21, 2009, 08:59:00 PM »
Measure the junction of the 10K/47K/100K and there should be voltage there that directly connects to the base. It's possible that you might have a short to ground on the transistor pins too.

I would bet it's a bad solder joint.

aron

Re: debugging
« Reply #3 on: September 21, 2009, 09:11:33 PM »
Here's a picture out what the voltages should be like:

http://i92.photobucket.com/albums/l9/generalguitar/BoostDebug.jpg

Keywords:

voltage, measure, collector, base, DMM, voltages, beginner project voltage
« Last Edit: September 21, 2009, 09:14:20 PM by aron »

emstin1

Re: debugging
« Reply #4 on: September 21, 2009, 11:29:13 PM »
well, i redid the joints, and replaced the battery with a fresh one. i get the correct reading for the collector, and the base actually registers now, but its still too low. and the emitter still gives zero.  back to the drawing board...

emstin1

Re: debugging
« Reply #5 on: September 22, 2009, 11:23:10 PM »
thanks for the picture Aron.  i read through the debugging pages on here and GEO and i found i had a short somewhere going to ground (if i said that right)  fixed it, i have sound  but it has a volume drop , and it has no highs whatsoever, like turning the highs all the way down on your amp and and the tone knob on your guitar on 1.  I'm guessing its still a solder joint somewhere because the base and emitter of the transistor are still not coming up with the right voltage readings. 

aron

Re: debugging
« Reply #6 on: September 23, 2009, 09:21:30 PM »
Bummer, yeah, still some sort of solder joint or bad wiring somewhere.

Cachao

Re: debugging
« Reply #7 on: October 27, 2009, 05:42:34 AM »
how do you measure transistor voltages? I don't think I'm doing it right since I am not coming up with anything and all I get is a volume cut when I plug the pedal in.

aron

Re: debugging
« Reply #8 on: October 27, 2009, 05:46:01 AM »
Red probe on transistor pin, black probe on ground of circuit. Meter set to DC.
If you don't get voltage, then maybe it's a bad solder joint with the battery clip.

Cachao

Re: debugging
« Reply #9 on: October 27, 2009, 05:58:15 AM »
Ok, thanks-I'll try that, but I think the battery solder joint is fine-I've checked many times.

Cachao

Re: debugging
« Reply #10 on: October 27, 2009, 06:05:13 AM »
Well I did as you said, put the black probe on ground and red on each pin and got no voltage whatsoever, but when I put the black probe on ground and red probe on the base I got a popping sound through the amp.

Cachao

Re: debugging
« Reply #11 on: October 27, 2009, 07:17:16 AM »
Maybe it's the wrong type of transistor? It's a 2N 2222A and I bought it from Maplin UK

aron

Re: debugging
« Reply #12 on: October 27, 2009, 03:10:36 PM »
> Well I did as you said, put the black probe on ground and red on each pin and got no voltage whatsoever

OK, do this. Put the black on the negative of the battery, red on the positive - do you see voltage?

If so, then believe and trust your meter. Despite what you may believe (it took me a while too!), there is no voltage going to the circuit. Your test is to find out why. It's not the transistor  - it's a wiring mistake. You do have the guitar cord plugged into the input of the circuit right? That will turn the circuit on assuming you are using the standard stereo input jack method.

Cachao

Re: debugging
« Reply #13 on: October 27, 2009, 03:58:11 PM »
I think that is where the mistake is-I didn't understand why the ring of the input jack had to go to negative of the battery, so I just sent it to ground-is that it? How does this work?

I am getting full voltage from the battery and it is going to the circuit board correctly, I have checked all connections.

aron

Re: debugging
« Reply #14 on: October 27, 2009, 05:34:29 PM »
>I am getting full voltage from the battery and it is going to the circuit board correctly
> Well I did as you said, put the black probe on ground and red on each pin and got no voltage whatsoever

Then your problem is between the battery connection to the board and the pin of the transistor. There's a break somewhere.

Cachao

Re: debugging
« Reply #15 on: October 27, 2009, 06:17:33 PM »
Well, I don't know what changed, but I am now getting 0.9v off the base and 0.4v off the emitter and collector. Still getting a volume cut though.
« Last Edit: October 27, 2009, 06:51:19 PM by Cachao »

aron

Re: debugging
« Reply #16 on: October 27, 2009, 10:27:07 PM »
> and 0.4v off the emitter and collector

That cannot be correct. Therefore you have a short somewhere with the emitter and collector among possibly other problems.

Cachao

Re: debugging
« Reply #17 on: October 28, 2009, 12:44:55 PM »
I've gotten rid of the shortcircuits I had, but it still doesn't work :( Between the collector and emitter pins, when I measure the resistance I get a slight reading telling me they're connected-but not so much that they are completely connected-ie by a lump of solder right on the track or the pins touching. (though it is worth bearing in mind that the soldering round there is pretty awful)

aron

Re: debugging
« Reply #18 on: October 28, 2009, 12:50:01 PM »
How are you wiring this? Perfboard? You may need to start over or keep on debugging. The meter doesn't lie. There is a mis-wiring somewhere.

Cachao

Re: debugging
« Reply #19 on: October 28, 2009, 01:07:11 PM »
Veroboard (I think-it has tracks). So the meter is meant to read that there is no connection between the two pins?