Smothie not phasing

[aballen]

Not sure where to look but I just got my smoothie together, matched jfets and all.  Unfortunately I only get clean sound... that is, when the pedal is off, I get a clean signal... and when it is on... I still get sound... but no real phaser effect.

I'm hoping you guys can suggest what I should be looking at and or checking... usuallu if I have a problem it is I get no sound... not clean sound.

[madbean]

What type of transistors and did you match them yourself?

[aballen]

Matched 2N5457 from small bear.  I actually ordered 50 so I could match them myself.. but due to the discontinuation of through hole jfets they said they could not fulfill my order... and offered me matched sets instead.

I did socket them.. .and I have one more matched set I could test.... assuming they were matched properly.

[gtr2]

You could always double check the matching and rule that possibility out.  I always double check gains etc. but smallbear is usually ok.

Josh

[aballen]

yeah, that means I have to etch a board for the jfet matching... I was hoping to avoid that by gettign matched fets....

any other suggestions?

[jkokura]

I've had similar problems, and usually it relates to a broken trace or a bad connection.  Check your soldering, check your pot wiring...

Jacob

[midwayfair]

yeah, that means I have to etch a board for the jfet matching... I was hoping to avoid that by gettign matched fets....

any other suggestions?

You can breadboard the matcher very easily. But before that, I'd assume there was a problem on the board and go through with a multimeter and checklist the components.

Check continuity into the "phasing" circuitry after IC1 pin 1 and verify that there's a voltage swing happening at the FETs -- this will partially eliminate the LFO as the source of the problem. I seem to recall the voltage swing being a few volts +/-, so fairly dramatic. You might also want to get out the probe and check if anything's happening at pins 1 and 7 of both ICs. If it works "right" on both pin 7s but not at IC2 pin 1, the problem could be related to the "mixing/balancing" circuitry -- use the wrong resistor on, say, R16 and you'll get no effect!

[aballen]

sigh... no time for trouble shooting tonight... but I appreciate the feedback....

baby board components are going to be a PITA identifying, especially all the caps... which pretty much look identical.

I'll let you guys know what I find, thanks again.

[Scruffie]

Yeah, post your voltages, it could be any number of things besides matching.

[aballen]

Ok I finally got some time to rig up a beavis board(should have done this a year or two ago)  and I got some voltages.  Just, powered up(I'm not strumming any measuring or anything like that).  I'm not sure what all to look at... I'm a decent builder, but I don't really know the ins and outs of opamps and phasers.  I really would appreciate some help here though.

250K trimmer, 500KC pot. 

Here are my voltages.

Voltage to board = 9.16V

Q1
G: 0.43V
S: 3.47V
D: 3.63V

Q2
D: 3.63V
S: 3.56V
G: 0.43V

IC1
P1: 3.64V
P7: 3.47V

IC2
P1: 3.79V
P7: 4.71V


Here are a couple of photos, in case you guys have better eyes then I.





Please let me know if any of these voltages seem off, or if you see anything wrong on this board.

Thanks for the assistance guys.

(side note, my cave dweller and afterlife work perfectly... so there is that )

[midwayfair]

Looks like the bias pot pin 2 just isn't soldered. Maybe?

[aballen]

It is soldered, the whole board is good(solderwise)  I checked there are no cold solder joints either.  I think the pic just looks a bit darker on that via, but its a good joint.

Do the voltages mean anything to you guys?

I'm not sure what to look at next.

Just to recap, when I plug it in I get sound, the tone changes a bit, but no phasing.

[Scruffie]

FET Gates seem too low and one of those OpAmps should have a shifting voltage (the LFO).

[aballen]

That is good info.  What parts does this make suspect? 

[aballen]

Well I have a pretty case for it waiting... still no luck figure out the problem though.

Any suggestions on what the voltages point to, or suggestions anywhere else?

I even went so far as to make a nice case for it.  Can't have this go to waste!