Tone pad pulsar

[lizardking]

I'm not too good with schematics but the way I read the tonepad pulsar schematic one pot is a variable resistor and the other is a normal potentiometer.  The tone pad PCB layout has both as variable resistors.  Am I looking at it wrong???

My tone pad only makes a clicking sound.

[mremic01]

A pot IS a variable resistor, but you mean in how they're being implemented in the circuit? I'm looking at the Pulsar schematic right now, and it looks like R10 (Depth pot) should have R5 and Q1 connected to lug 3, and lug 1 and 2 are tied together and connected to R11. R15 (Rate) had lug 2 (middle one, which is the wiper) connected to C8. Lug 1 is connected to one side of R14, R20, and Q3. Lug 3 is connected to the other side of R14 and R16.

It sounds like the issue you're having isn't with the pots though. I'd go over everything twice and start a debug thread if you can't find the problem.

[lizardking]

Thanks.  That's definately NOT how the tonepad PCB is laid out.  The wiper of R15 should go through C8 to the base of Q2.  It should NOT continue on to the collector of Q3 as it does.  Instead that trace should probably duck under C8 and go up to pin 3 of R15 which should NOT be connected to pin 2 as it is.

I'll have to see if there are any other bugs in the layout...

[mremic01]

It looks like I wrote R5 where I meant R6 in my last post, so that's not an error in the project document.

I realized what you meant about one of them being a normal pot and the other being a variable resistor. R10 is just acting as a variable resistor. R15 is a voltage divider, at least in the schematic. Though I'm just a learner and I could be horribly wrong.

Now the layout isn't clear which lug is 1 or 3, and really that only matters if you want the pot to function from left to right or right to left when turning it. So I'm going to assume that the layout's solder pads are arranged as if we were looking at a pot from behind, with the lugs ordered 3, 2, 1. But then it show's R15 as a resistor with the two leads crisscrossed. Ugh. So let's assume that while R10 is 321, R15 is being shown as 123 on the solder pads. So the layout has 1 and 2 connected and on the same node as R14, C8, R20, and Q3. The schematic has R14, R20, and Q3 on the same node with what I'm assuming is lug 1 of R15. And then lug 2 isn't connected with lug 1.

Now it might be that the location of C8 doesn't matter. It seems like one of those situations where it just needs to be on either side of the pot and it will have its desired effect. You'll find a lot of layouts that do that with resistors and caps when it makes for a tidier layout even if the schematic had it the other way. But I could be horribly wrong about that too. The thing that looks like it would cause problems is having the wiper connected to lug 1. I'd definitely try connected things like in the schematic if you can to see if that solves your problem.

[Lizard King]

Thanks.  I get the pot numbering thing....though I generally hook mine up backwards and have to switch once I start playing with them - D'OH.  It's an easy change to the PCB layout.  I'm just surprised no one else has had any trouble - although as someone pointed out in another thread, tonepad removed all their build reports so this might be a well known problem.

I was just looking for a simple tremolo - something a bit easier to build than the tremulus...but I could probably go back to that design...

[duck_arse]

(so many lizard kings)

have you looked at/thought about one of the ea tremolos or variants? they don't get much simplerer.

[Lizard King]

I haven't tried that one yet.....I was just looking at my Tremulus laying again - I wanted to add all the bells and whistles and Tonepad's layout didn't have any of the extras.  What does the EA sound like?

I also found a design on here for the tiny tremolo.  That looked painfully easy too.  The thing I liked about the pulsar is getting a square wave output.  I have a stutter box but if I could get the tremolo to do that I could eliminate a box.

Of course I've gone back to my trusty SGX 2000 multi-effects rack so now I'm just playing around with boxes....If I come up with a really cool effect I can run it in the SGX's effects loop...