bsiab freakout. 1 worked, 3 do not...

[nag hammadi]

hi guys.  here is my issue...

i built the bsiab 2 using one of the ggg boards.  i didn't have j201's, so i used nte 458's.  it worked flawlessly and sounds great.

i decided to make three more (one of them is hand wired, point to point!) for myself and friends.  i ordered 3 more of the boards from ggg.  i doubt it matters, but these boards were much smaller than the first.  were there any changes?

i decided to go EXACTLY by the plans / parts list on the ggg site (meaning i used j201's).  i followed the layout exactly in terms of everything including the orientation shown for the j201's.

EVERY one of the new 3 pedals are doing the same thing.  i get a good sound when the trim pot is turned all the way to one side, but with 1/2 the volume of the bypassed signal (even with all of the controls all the way up).  as i turn the trimpot towards the other side, the volume decreases until it is totally silent at the end of the range.

i have gone over all of the connections thoroughly, and everything seems fine.  the fact that the EXACT SAME THING is happening with ALL THREE (even the p2p one) leads me to believe there is something else going on.

is the orientation listed for the j201's wrong on the layout?  did i get a bad batch of trim pots (how do i check that?)?

should i just go back to using the nte 458's instead of the j2o1's?  seems like it should work with the j201's though since that it what is called for...?

i would greatly appreciate any help.

emanual

[dano12]

I think it's unlikely that you got bad trimpots. More likely misoriented transistors, a wrong value in the wrong place, a solder bridge or something like that. Here's a couple of photos of my GGG BSIAB 2 build, you should be able the check basic orientation. Hope it helps!

[nag hammadi]

yeah, i am REALLY REALLY smart.

turns out 100 ohm trim pots look just like 100k trim pots...

good thing NASA fired me when they did... rocket science and all!

put the correct trim pots in and whammo!  sonic bliss.

now eat your vegetables and call your mom. 

[Connoisseur of Distortion]

could you post a picture of the PTP BSIAB?  sounds like a pretty serious rat's nest!

[nag hammadi]

i will try to get some pics up this evening.  i actually thought it may be easier because it is how i make my amps.  i was wrong...  way harder.