Beginner Project Lacking in volume again. . .

[ryanscissorhands]

Following the "What to do when it doesn't work" sticky. . .

1. Two days ago I decided to start from scratch, and rebuild my beginner project. It worked first try! That is, until I undid some stuff to wire it up with a 3PDT switch. And  I did test the switch.

Again, the same as my first attempt, the volume is louder when bypassed.

2. Beginner Project (Gus Smalley's NPN Boost)

3. Source--this forum. Aron's layout

4. Modifications: 2N2222. I would have gone with 2N5088, but I don't have any.

5. Part subs? I'm using a 10k pot instead of a 5k pot, but that shouldn't matter since I test with the pot in different positions.

6. No pos-neg conversion.

7. Battery Voltage: 8.92V
(Let me mention that I only get volume when the transistor is in what I believe to be the wrong way. I checked the datasheet for 2N2222, and it seems that the "arrow" made by the pins should point towards the input, from what I reckon.)

Ground-Board Positive: 8.93V

(With Transistor supposedly in the "wrong way")

Base: 0.65V
Collector: 7.67V
Emitter: 0.14V

(With Transistor supposedly in the "right"way)

Base: 0.24V
Collector: 8.85V
Emitter: 0.00V

Obviously the one with 0.00V at the mitter is wrong. . .

I've checked every solder joint to amke sure that ther eis concinuity, and have scratched between all pads that are not supposed to be connected.

Any ideas? I have some 2N5088's on order. If I sub that in, should it give more gain? Or is this something that I should try to deal with now, and not just ignore?

Thanks.

EDIT: I also posted this in the beginner forum, but i'm pretty sure few people check it nowadays. Except newbs like me.

[petemoore]

steel can type 2n2222, the tab sticks out toward ground/emitter.
plastic body 2n2222 the markings on the transistor face output.
 Check the data sheet for your transistor.
 It only works being oriented correctly, I've turned them around like that before, it's probably still good.
 Beginner project - NPN boost...
 I think that's a 'conventional' bias setup, anyway the base must be .6v or more above the emitter for an Si to operationally amplify, [the higher it is after that takes away from the maximum swing before the transistor 'runs out of room' from PS limits'
 There should be voltage readings from the NPN boost available in the B section, I'm guessing the collector needs to be somewhere about 1/2v for the circuit to operate optimally.
 Your voltages indicate a bias problem, probably a miswire from a short or something came loose...you did say it was working.
 Eliminating the change that caused malfunction is one technique, I'm sure you've looked for the short/open that shouldn't be there.
 Other than that you can pull the transistor and apply the DMM to find if any of the resistances of resistors on your board are lower than specified, higher value read probably is caused by an alternate path created when the R is in the circuit.

[seanm]

5. Part subs? I'm using a 10k pot instead of a 5k pot, but that shouldn't matter since I test with the pot in different positions.

Actually, this will affect the bias of the transistor. From the transistor DC bias point of view, the pot is just a straight resistor to ground. When you get it going try to get a 5k pot. Your max volume should go up a lot.

7. Battery Voltage: 8.92V
(Let me mention that I only get volume when the transistor is in what I believe to be the wrong way. I checked the datasheet for 2N2222, and it seems that the "arrow" made by the pins should point towards the input, from what I reckon.)

Correct. The "arrow" points to the base (the input). A little metal tab on the case should be near the emitter (the gain pot connects to this).

[ryanscissorhands]

Well, if it's supposed to be oriented with tab towards emitter (as you say, and as the two datasheets I referenced showed), then it only works with the transistor backwards. That sounds like it's not a good thing to me.

Regarding the 5k versus 10k pot, from what I understand (which could be way off), it shouldn't matter because there is not value that a 5k pot can get that a 10k pot can't get, so as long as I set it right, there shouldn't be any problems, right?

I got frustrated, and as you know, trying to debug while frustrated is no good. I would be better off trying to inhale a tornado. So I went to work on the enclosure. Once I get paint on it, I shall return YET AGAIN to my circuit, and see what else I can come up with.

(By the way, the other frustration I had last night was htat my 9V battery was reading near 13V. And so was every other 9V battery I could find. Alas, it was that my DMM battery was going. And getting that thing open--even more frustrating. I think I need to eat some chicken and chill.)

[seanm]

Regarding the 5k versus 10k pot, from what I understand (which could be way off), it shouldn't matter because there is not value that a 5k pot can get that a 10k pot can't get, so as long as I set it right, there shouldn't be any problems, right?

No. Take a pot. Measure the resistance on the two outside lugs. Now rotate the shaft. The resistance dosen't change and should be the value of the pot. The resistance only changes between the center lug and the outside lugs.

Edit: use petemoores suggestion below. Way better than mine.

[petemoore]

Strapping a 10k resistor across the 10k pot should bring it to right around 5k..try that, it need to be done or use a 5k pot anyway, that 'might be all...

[ryanscissorhands]

Well, I tried the 10k resistor across lugs 1 & 3 on the pot--same thing. I then decided to try avoiding the pot altogether, and put a 4k7 resistor to ground from the emitter with a 47uF cap in parallel to ground, and still I get nothing.

The weird thing is that I do get SOME volume and a reading when the transistor is in the wrong way, but when it's in the right way, 0.00V at emitter and nothing but noise.

I've done so damn much soldering and desoldering that it looks like a mess. Well, no, it IS a mess. I've checked all of the things that I know how to check, so again, I think I'm going to give up and start over. For the time and frustration that I've put into debugging this thing, I could have built a few of them and picked the one that works.

I'm using this crappy RS perfboard that doesn't fit conventional socket sizesm and it's making it hard to fit everyting in anyway. I'm ready to start from scratch again, unless anyone can think of enything else.

I must admit that it's a little discouraging to have failed my first two attempts at the simplest project available on the internet. But not half as discouraging as it is frustrating.

At the same time, I will NOT be defeated by the beginner project. I usually do better with challenges than cakewalks. At least the paint job is turning out a little better. . .

[seanm]

I would recommend buying a solderless breadboard. I always breadboard the effects first. Then I know all the components work.

[seanm]

Ok, I breadboarded the NPN boost using a 2N2222A. I used a 10k pot with a 4.7k resistor in parrallel (petemoore's suggestion).

V 9.1  C 2.9  B 2.6  E 2.0

I then reversed the transistor. It worked fine.

V 9.1  C 6.2  B 1.6  E 1.0

I then removed the 4.7k parrallel:

V 9.1  C 7.0  B 4.7  E 2.1

I think you should check the resistor values. In this effect, the caps do not affect biasing.

And this isn't the simplest effect... the Bazz Fuss has almost 1/2 the parts!