basic transistor help.

[thejoe]

New to non-kit builds. Trying to build boosts and Fuzzes with different trannies. From what I understood npn could be basically swapped for one another. I've been trying the lpb 1 with a 2n2222 but it won't work. What am I not understanding?! Is there so!e place I could be directed with info that really breaks it down?

[tjdracz]

It should work fine with 2n2222 as long as you got pinout right. Does it work with 2n5088 or so?

[thejoe]

I don't have any others available. I think it might actually be my breadboard now that I've tried more failed builds.

[armdnrdy]

Get a new breadboard and get a 5088.

The 5088 has a higher current gain. (HFE)

A 2N2222 will work but...the circuit was designed around the 5088 or tranny of equal gain.

[thejoe]

Get a new breadboard and get a 5088.

The 5088 has a higher current gain. (HFE)

A 2N2222 will work but...the circuit was designed around the 5088 or tranny of equal gain.

That's basically what I'm getting at... What part of a data sheet would relate to proper gain and other compatibility?

[armdnrdy]

Look for HFE on the data sheet. Find something similar.

[LucifersTrip]

Just like with any other troubleshooting, voltages will help...

When I built one, I posted the info, especially to help out beginners.

Bottom line, the hfe of the transistor does matter alot on this one (5088 was too high) and you it helps
to have a buffer in front.

http://www.diystompboxes.com/smfforum/index.php?topic=104730.0

[thejoe]

Just like with any other troubleshooting, voltages will help...

When I built one, I posted the info, especially to help out beginners.

Bottom line, the hfe of the transistor does matter alot on this one (5088 was too high) and you it helps
to have a buffer in front.

http://www.diystompboxes.com/smfforum/index.php?topic=104730.0

Excellent. This is making sense now. Thank you.

In addition, how do I know what my voltages should be? I know how to check them but not what to reference to see if they're correct. And, if I were to use a 2n2222 would I just be able to adjust the bias resistors to bring it up to functioning ability?

[GibsonGM]

Collector should be near 5V, base should be ~.8V, emitter should be ~.15V, as referenced from ground.

I'd think that the circuit would OPERATE ok with a 2N2222,  but just won't have the punch you probably want.   It's certainly ok to pop in different  BJTs to see what you think!  Mind the pinout, of course. 

[LucifersTrip]

Excellent. This is making sense now. Thank you.

you're welcome

In addition, how do I know what my voltages should be? In the post I know how to check them but not what to reference to see if they're correct.

In my 1st post I stated the voltages from my friend's original:
http://www.diystompboxes.com/smfforum/index.php?topic=104730.msg940166#msg940166
(yes, 5V on C)

And, if I were to use a 2n2222 would I just be able to adjust the bias resistors to bring it up to functioning ability?

Yes, see the other post from PRR:
http://www.diystompboxes.com/smfforum/index.php?topic=104730.msg940294#msg940294

[thejoe]

But those voltages are only for this pedal, right? How would I know what is correct for other pedals/transistors?

[duck_arse]

you tell the transistor the voltages.

set the base voltage with the 2 resistors, V+//base//ground, straight voltage divider, ohm's law (rules, OK?). then subtrack ABOUT 0V6 from the base voltage, and this is the emitter voltage, something to do with p-n junctions at work there. the Emitter voltage is across a resistor, which will give you a current,  via Mr. Ohm again. now apply that current across the collector resistor, series circuit current is the same, Mr. Ohm style, and you will have another voltage to subtract from V+, and THAT is your collector voltage.

this is just rule of thumb, but works well enough.

[PRR]

LPB1 is over-sensitive to Vbe (as well as hFE).

Neither Vbe or hFE is well-controlled in production so data-sheet only gives wide ranges.

Ideally you find the same batch of transistors as Mike bought; or you diddle the base resistors *slightly* to get the collector roughly half-way between 9V and Zero. (There's a few different values floating around, suggesting that Mike had to re-diddle for different batches.)

[LucifersTrip]

But those voltages are only for this pedal, right? How would I know what is correct for other pedals/transistors?

That's one of the main reasons forums like this exist. Each pedal is different....you'll usually find threads with people talking about the voltages.
The holy grail of info (other than the schematic) are the voltages from good sounding originals...The people cool enough to post those usually
get a bunch of thanks, especially if it's from a rarer pedal.

So, yeah...a part of building is researching each pedal before you start.

[thejoe]

You have all been very helpful. Thank you.