bad stone revisited

[lowstar]

hi everybody,
i checked my bad stone again, because i was never sure about the feedback pot...and now i compared the sound samples on zero´s site with my build and i think the feedback pot is not working as it should be.
when it´s fully open, the output of the whole phaser is attenuated, that´s not right ?
also the phasing is not as strong as i think it should be.

maybe i messed up somehow with the offboard connexions ?

i have it hardwired to auto mode, so

• jumper between E and F
• 100k resistor from G to ground
• J goes to lug 2+3 of the 100k pot
• lug 1 goes to L
• L also connects to one pin of an spst switch
• the other (middle) pin of the spst connects to M

does anybody spot a mistake ?

i spent this morning with the bad stone instead of boxing up the polyphase, aarrgh !
but i can never stop until something is working correctly. 

cheers,
lowstar

[lowstar]

found the darn mistake ! arghh ! 
a broken trace on the pcb from pin 1 of ic D to both c6 and r14...
...i built it on march 29th...uh oh...was sitting on my uncompleted bench since then, every time i got bored or did not know what to do next, i fooled around with it to find the bug...(at first when i built it, i thought it worked, cause it did kind of phase, but much too weak)
so the phasing never reached full volume, that´s why the end product sounded kind of attenuated with feedback on full...ts ts ts
it was one of my first self-etched pcb´s where i had problems with underetching the traces (the brassmaster gave me similar woes).
that very connection i had even covered with solder completely...but the trace disconnuity was too much to be covered by soldering over it, so i had solder a little piece of wire over that trace.

well now i´m gonna revisit that resistor trick to make it unity gain...if it still unsatisfactory, i´ll tack an op-amp gain recovery stage at the end.

see there´s a good side to everything, i actually had a motorbike accident and that´s why i was sitting here with a bandaged left hand trying to fix the critter 

cheers,
lowstar

[lvs]

Congrats and some empathy from me, lowstar.

An EH Bad Stone without bottom plate was given to me years ago, out of a garage from under some car parts. Past week I finally gave it a go. After reconnecting some loose wires and bridging copper trace cracks, the manual sweep worked - yay - but the LFO stalled. I was hoping for the simplest cure in the form of new caps, but it worked only after replacing the LM324. I socketed it - I was interested to see that different opamps don't work there.

After a few similar cases I feel it's better for me to go all the way instead of giving a still defunkt circuit a long rest risking to forget what happened underway.

Almost needless to say the forum was a great help, if it weren't a way to say thanks. Searches returned what I needed, I didn't have to ask questions.

Cheers,
Lucas