Hope this helps save some time for those of you frustrated with properly biasing Wampler clones and working with smds...
After reading this post from Induction
, and this one on DIY
regarding Wampler designs, I've ditched the trimmers and have gone back to using the original drain resistor values.
And based on this suggestion by lars-musik
, I built a stripped down version to sort through my smd J201s.
I used a 2P4T rotary to select drain resistor values 5.6k ('65), 15k (plexi), 16k ('57) and 22k ('57 & Pinnacle). Of course the rotary switch isn't necessary, just a convenience.
Probably should have socketed at least 1 of the resistors and the source resistor to easily accommodate other designs, such as the Sovereign (27k drain and 2k2 source)
I used a row of 5 SIP IC sockets with 24 gauge wire to make standoffs to mount the smd converter board and a post for an alligator clip for the black multimeter probe. I cut the gate and source posts short and left the drain post long to accommodate an alligator clip for the red meter probe. (one of the SIP sockets isn't used, just there to keep the entire row sturdy)
The smd converter board and the SIP sockets make a nice little platform to test the smds. I used the side of my needle nose pliers to temporarily hold the little buggers in place. Took a few times to get the hang off it.
It took about 2 hours to sort through 100+ SMDs looking for drain voltages between 4.5 and 5v with the various drain resistors. Found multiple candidates for all but the 5k6. (black '65 - ordered another 100 smds from Newark to see if I get any hits with the 5k6)
I randomly picked 3 of the sorted "15k" J201s, soldered them to their own adapter boards and popped them into my latest plexi drive. All 3 read between 4.5v and 5.0v in the pedal. Whew!
Now I'm set for a few more Wampler builds.
2P4T mini rotary
(I can spare a couple of these if anyone is interested as I have 14 of them)
smd adapter boardSIP Sockets and the little buggers
posts for allgator clips
hook up clips and meter
place smd in position
hold smd in place while taking reading and adjusting switch
1978 Gibson Les Paul Standard, Cherry Sunburst