Author Topic: Performs as predicted but with 1/3 the output  (Read 6827 times)

kleydj13

Performs as predicted but with 1/3 the output
« on: May 25, 2010, 04:05:59 AM »
I built the beginner project following the instructions provided and I'm not getting sufficient output.  It works as I would expect it to, but it has only 1/3 of the expected output.  It is much quieter than the bypassed signal. 

I've gone through the instructions and the layout many times.  I've set it down and come back for a day a few times and I can't figure it out.  Any suggestions on where to look for problems?

I've tried using a multi-meter to read some voltages, but I'm not entirely sure how to use it.  I have built successfully a few BYOC and GGG kits no problems.  I've also rewired my guitars a billion times.  My soldering skills aren't great and I can be a little sloppy, but it works. 

The reason I really am confused and want to post this is because I have also built the Tweak Fuzz project found on Small Bear's website and a EHX LPB-1 project that I put together by following the layout from GGG's website and others on the web.  The weird thing is that all of these projects I've built display this problem consistently.  Each of them have very low output.  I used a traceless breadboard from Radio shack to hold the components together.  I sought the beginner boost project to improve my building techniques thinking maybe some of the signal is lost in my poor construction methods.  I tried to follow the instructions as closely as possible and connect components as neatly as possible. 

What am I missing here?  I'd love to get these to work as I've had a lot of fun building these projects and would love to continue to learn more and build more.  I have limited knowledge about electronics in general but am eager to learn.  Let me know if you need any more information on anything.  Thanks in advance. 

aron

Re: Performs as predicted but with 1/3 the output
« Reply #1 on: May 25, 2010, 05:05:35 PM »
How is your transistor oriented? Can you measure the voltages on the 3 pins with respect to ground?

kleydj13

Re: Performs as predicted but with 1/3 the output
« Reply #2 on: May 25, 2010, 06:35:09 PM »
How is your transistor oriented? Can you measure the voltages on the 3 pins with respect to ground?

The round part of the transistor is pointed away from the big green capacitor.  I'll try to get some voltages up. 

kleydj13

Re: Performs as predicted but with 1/3 the output
« Reply #3 on: May 25, 2010, 06:42:39 PM »
I just took some voltages.  I think I did it right.  I plugged in the battery and a cable into the input jack to turn it on.  Then I put the red lead on the target joint and the black on the ground joint. 

C - .880
B - 3.25
E - .863

kleydj13

Re: Performs as predicted but with 1/3 the output
« Reply #4 on: May 25, 2010, 06:48:56 PM »
I've been looking over the whole thing and comparing it to the instructions.  I just remembered that I haven't noted that I have a few values a little off as I didn't have all the exact components.  My output cap is 4.7 uf, my pot is 1K, and the cap on the pot is 68 uf.

I have no idea what sort of transistor I'm using.  All these parts came from Radio Shack and most of them came from a variety pack of resistors, capacitors, and other stuff.  I tried to put in values as close as I could find.  I thought it would still get me in the ballpark. 

I'm wondering now especially with the pot being 1k instead of 5k if that is where my output is being restricted.

Load3r

Re: Performs as predicted but with 1/3 the output
« Reply #5 on: May 26, 2010, 09:55:13 AM »
Quote from: kleydj13
I just remembered that I haven't noted that I have a few values a little off as I didn't have all the exact components.  My output cap is 4.7 uf, my pot is 1K, and the cap on the pot is 68 uf.

I have no idea what sort of transistor I'm using.  All these parts came from Radio Shack and most of them came from a variety pack of resistors, capacitors, and other stuff.  I tried to put in values as close as I could find.  I thought it would still get me in the ballpark.



Your voltages seem to be off. Collecter is at 1/2 of expected, base and emitter less than 1/3 (corresponding to 1/3 of output maybe?) Could you check your voltages at the other two points show above? Or maybe give us a rundown of the resistor values you ended up using.

Is there anything written on your transistor at all? Post up whatever is there and I (we?) could help track it down. You could test it in your multimeter (assuming it has an hFE mode) to figure out which pin is what.

Not sure about the cap values, but I believe a lower valued pot would just give you less available boost instead of reducing overall output.

kleydj13

Re: Performs as predicted but with 1/3 the output
« Reply #6 on: May 27, 2010, 02:17:31 AM »
I don't have a 47k resistor so I put in a 56K in its place.  I have a 1k pot with a 68uf cap on it.  My output cap is a 22uf instead of 10uf.  I found another transistor with markings and put it in.  It says:

CEN2N
5089

and it has markings for EBC.  I have the flat side towards the green cap so that E is the lowermost leg.

I took some pics of my build. 





Load3r

Re: Performs as predicted but with 1/3 the output
« Reply #7 on: May 27, 2010, 10:34:29 AM »
That new transistor is 2N5089, perfect for the project. No problem there.

The caps ..... their effects are still beyond my grasp. I hope someone else can chime in on that topic. But if you put two 22uF in parallel (side-by-side) it will equal 44uF which should be close enough to 47uF for the gain pot. If you take those same two 22uF caps and put them series (back-to-back) you would arrive at 11uF, which should suffice for the 10uF output cap.

As for the resistors, the 56K (due to 10% tolerance) could be anywhere from 50.4K - 61.6K
The 47K would have been anywhere from 43.3K - 51.7K

The two resistors have a small window of overlap at their extreme tolerances only. For a lot of instances this would be fine, but the 47K is part of the bias network and might be the problem.

You could do some resistor math to get you close to 47K. If you have more 100K's hanging about, you could put two in parallel (side-by-side) to get you to 50K which is closer. Now if you check them with your multimeter and find two that are (due to tolerance) actually somewhat under 100K, then that would bring you even closer to 47K. Two @ 94K would be bang on 47K (in parallel).

Below is a link to a website with online calculators to figure out resistors/capacitors in series or parallel, as well as a program you can download to do it offline. You can even use it to identify resistor/capacitor values based on the markings on the component. Very handy!
http://www.electronics2000.co.uk/

I hope that helps!

Gus

Re: Performs as predicted but with 1/3 the output
« Reply #8 on: May 27, 2010, 05:24:47 PM »
Use a 5K pot, it is part of the bias setup and the design.

ArmOnFire

Re: Performs as predicted but with 1/3 the output
« Reply #9 on: July 20, 2010, 02:32:35 PM »
When I first built this project I had the same problem.
It turned out to be the transistor was installed backwards, and acted as a signal attenuator instead of a signal booster.
Good luck.
-Dan