not getting the full volume

[mikechang]

hi all:

i was working on the Muff Booster from AMZ's site, but my volume when i switch into circuit is sorta low compare to the bypass volume
i wonder what could have caused it??  i turned my 100k pot, it works... so i'd say it's not the problem....?
would uploading my circuit picture help??  it's very messy....
seems like im not using any wrong resistor/cap values....
and i tried to replace the BJT....doesn't work  (im using 2N3904)
i'll doulbe check on my wiring again....
here's the AMZ muff booster schematic: http://www.muzique.com/schem/muff.gif

thanks.....

[mikechang]

i just made another same circuit , and the result came out to be the same.....
what exactly is going on??
i simulate this circuit with PSPice, and i'd get about the same amplitude as input, but offset by about 200mv (while input is 500mv sinwave)
could i be doing something totally wrong??
what should my output waveform look like for this "booster of 30db" ??

[mikechang]

yea i know it looks ugly......
the switch is for bypassing the cap+diodes

[GibsonGM]

Hi guys,

I built that puppy before...took the diodes out and just used it for a  clean type booster.  It should be LOUD!  So there's a problem.

Check:  is BJT oriented correctly?  Are polarized caps oriented correctly?  Diodes in the right way?  Is the pot wired correctly?  Ya sure that switch is wired up the right way? Double check....also look for shorts caused by solder bridges.

Then:
What voltages are you guys getting on the 3 pins of the transistor? Black probe to ground, hit each in turn with the red probe & record those values and post back. ( I know you know how to do this, I'm just making sure;o)  Include battery voltage.   

An audio probe might locate the trouble right away, by following the signal thru the input and BJT...tell ya right where the trouble is.   Read the "Debugging" thread, and try searching for "audio probe".
Get back with that info, and myself or another nice forumite will gladly try to point you in the right direction.  We'll get it working right, no worry.   

[petemoore]

   Soldering tips...
  Start with a good iron helps, clean tip that's good 'n hot and sharp is all that's necessary, cooler tip works but takes longer for the heat to sink in.
  The board looks pretty clean, but I always 'polish' them with cotton or paper..this'll shine them up and seems to make the solder stick' faster.
  Use heatsinks [I prefer socket though] for the transistor to maintain coolness.
  {OT?}...no, I like my left hand free so I can work faster, I mount my iron, only person I ever heard of does that. I found this speeds things up and increased my approach and retreat accruracy, and allowed me to get the tip in and out of the area to be contacted [soldered] cleanly and instantly from any angle of approach.
  But those look like cold solders. ie the metals which needed to get solder 'really' on 'em [all over and through them] did not reach the proper melting temperature of the solder.
  It starts with the only thing heated is the tip of the iron. Adding teeny bit of solder to a clean tip allows the heat to flow better when the iron touches something...
  So..with a clean, tinned, hot, iron tip..and clean parts [sometimes I cut the glue-ey end of the resistor off, other times I clean it real good, pinching it hard in a cotton rag and twisting/pulling the glue off, then polishing it some more]..so..all the metals to be joined are clean, in place, and physically touching as best possible.
  apply the tip to as much contact area as possible, hopefully contacting...as many of the different metal pieces as possible...get it on/in there 'good...
  add enough solder to catalyze the heat transfer process, the solder will transfer the heat from the tip to the surfaces of the metals much quicker than a dry tip...add no more solder at this time.
   Allow the small amount of *cold solder you just added [this'll cool the joint first with it's thermal mass being all cold' 'n stuff, then will heat, and transfer heat...allow time for the heat to heat through the metals before adding any more *cooling solder.
  Add a bit more solder, in passes [so it has time to heat and 'flow' into the joint], just a little at a time so the joint can 'flow'...solder will tend to 'wick' on to all the nearby metal surfaces, and the whole joint'll look more like a 'water droplet' than 'fast cooled lava', a semi-smooth appearance means the solder 'found' it's position while molten, a rough 'shard-like' surface indicated uneven heat, and cooling.
  Small amounts of solder at first [to fascilitate the heat transfer], so the metals have a chance to get warmed up [adding more solder cools the joint], then add little amounts in passes...until the joint has enough solder to be 'sturdy'..physically. As long as everything is heated and the teeniest bit of solder 'took' to all the parts, it'll be 'good'...but adding enough for a sturdy 'structure' is what I go for, then no more.
  It's really a balancing act. Hot Iron, cold resistor lead, cold pad, cold solder...you want the iron tip to be able to heat all these other items...so easy on the cold solder addition at first fewish seconds of iron tip heat...add just enough so the heat is transferring to All the metals...allow it 'some' time to do so before adding more, finish the joint with only just enough solder.
 
   

[petemoore]

  Follow the traces, and see if something isn't touching where it shouldn't.
  Follow the traces by measuring connections, and non connection points nearby with the DMM, beep mode.
  Measure the resistors values from the 'distant-est' points possible, this will also test any solder joints between the test points.
  Practice the soldering techniques, allowing the heat to sink in, and also...the approach/retreat and angles thereof look like an area for some improvement,
I mount the dern iron in a brick hole, then I have my left hand free to whip the board into approach positiion, my left palm is steadied by having a sturdy 'rest'...I steady my hand as it brings the board to the iron tip by having my wrist against a fixed object...then my fingers can to the ~1/2'' of the final approach to the tip of the joint to be soldered...very accurately...same with the retreat, I can easily be very careful about exactly where the board/tip relationships are while the board pads are near the hot iron tip.
  Everyone who has tried this 'mount that hot iron securely' technique has reported:
  Easier to manipulate board
  Quicker to manipulate board
  Using the hand to manipulate components into place and pin them there can be done by hand, fewer clamps or tape or other part manipulation 'item's are often no longer necessary.
  The soldering iron base, and the third hand can be removed from the work area.
  A palm-rest to steady the hand improves it's steadiness
  The iron never gets dropped
  The iron tip gets less 'whatever besides solder' on it
  Speed and accuracy improve
  Works great because the lighting and exhaust can be ...put right over the fixed tip/work area.
  The iron only needs picked up or set down when working an area which is not accessible with the iron mounted.
  When finished with the last solder job, the board is in your hand already.
  I got tired of wiggling, dropping, burning, messiness on the board, extra stuff...and figured out to mount the hot iron down securely, temporarily...see..the board I like to move around, get my fingers all around it, change the angles of it, do things to it like put resistors in it, having the board in my hand, and the iron out of my hand at most times...so I tried it and it improved everything about the way soldering is done...like putting the reel of solder on a nail so it is always right next to the soldering iron, I always leave that reel right there, rotating it on that nail until all the solder is used and replace it with a fresh one.
  If you are right handed, try mounting the iron at a down angle, pointing toward your left elbow or wrist, near where your eyes can easily look closely, and where your hands are comfortable working.

[mikechang]

amazingly weird!!  my circuit works now!!!
all i did was leave it overnight, and measured the biasing voltage for BJT (C=5.44v, B=0.7v, E=0.06v, which is very close to my PSpice siumulation)
then i thought, these numbuers wasn't that different compare to the simulation result, so i plug it on again, it works.....LOL
the only thing is the switch isn't working very nicely.....something's wrong with the clipping stage..... but i'll figure it out
also, it starts to pickup some radio signal....wth.......

thanks for your replies