Tweaked Obsidian woe's !! ??

[MartyMart]

Wanted to try a "P" channel Obsidian, using BS250p mosfets and some cap tweaks to
the standard circuit, it doesn't deviate much !
Obviously it's positive ground, so any electro's are reversed and I'm using 2u2 poly's from
the source's anyway - NP and also reversed the protection LED's on each gate/source.
With the original 3k9's to drains I was seeing 8 volts from an 8.5v battery, and almost no
signal, just occasional "blatt" when stummed hard.
Swopped them for 12k's and have almost the same reading !! ?
Can't get this to work, only by shorting the first mosfet with my finger across D_G_S gives
a second of full gain, but still "splatty"
Got fed up and put it away ....
Downloaded a BS250p data sheet which gives my pinout as D-G-S top to bottom, flat side
facing away, seems correct.
Ideas ?
Why the large voltage at drain ? the BS250p's are small with slight curve and silver sticker on the
curved side only says BS 250 p
( measurements taken with positive red DMM lead as ground, black DMM lead to drain.... of course )

Marty.

[WGTP]

On Joe's Obsidian with the BS250's, there aren't any LED's.  Might try removing them, I'm not sure the effect.  Might need to adjust the bias some more.  Those Mosfets are sort of like Jfet's when it comes to consistancy.   

[MartyMart]

Got the drains down to around 5v ...... with 150k 's  !! 
I must have the wierdest BS250's on the planet.
On all three it's about "
D 5.2v
G 1.13v
S 0v
Almost sounding right, though turn down gtr vol and it's " splatty City "  !

MM.

EDIT : Giving up on this one, I've knackered the vero with all the resoldering of drain resistors
and removing the LED's - which are not the problem !!
I'll rebuild one another time with trimpots and also try adjusting the gate/source biasing too, these
BS250's "suck" , when near to 4.5v they start to rise up towards 6v .... not biasing well at all.

[WGTP]

That's weird.  Might try flopping things and using BS170 or 2N7000 N channels, just to see if you can get it working right.

I see Mosfets as warm weather circuits, since the cold brings static electricity.  Good luck.   

[petemoore]

  I'd work with one stage first.
  Mosfets can be/are tricky to bias, 150k on the drain, I don't know what the Obsidian started with
  ...I would play with the gate resistora, see what happens to the D when the G voltage is moved'...maybe a different active would want to bias up better with the given R network.