alright. i'm assigning myself this three part project

[jlullo]

Alright.  It's about time  i figure out how to use a breadboard and learn how to do my own layouts...

So, i'm assigning myself to a pedal which i have already done, because i know how my first sounds, and would like to experiment with different trannys and diodes.

1.  use the breadboard
2.  figure out what components i like best
3.  make pcb layout

This is going to all be for the tonepad TS-808 project.

I'm going to post all of my problems and questions in this thread so that i don't hog up board space... because i'm sure there are going to be a lot of them.

Here is my breadboard:


the first red post on the left is a +5v power supply, then the next one is a +0-15v supply, and the last is a -0-15v supply.  For this circuit, i would be using the -0-15v supply, since it is a negative ground circuit, right?  How do i use my DMM to adjust this to 9v using the trimpot below it?

i know that the red and blue bars on the top are buss bars, and that those are used for power, right?  so i would attach a jumper from the power to the red buss bar, and the common to the blue?

as for laying out this circuit on the breadboard, i have read that it is best to start with the op amp and just branch out from there, highlighting the components that i've put on the board.  is this correct?

[KerryF]

1 question... Where did you get that breadboard 

Also, yes when breadboarding with ICs I place them first then branch out.  With some things like diodes you can put jumper wires to other parts of the board so that you can easily swap between different diodes for different sounds.  Check out Dano12's Clip Board for switching between clipping diodes and stuff.

[jlullo]

kerry,
craigslist!  i got a deal that i couldn't refuse

thank you for the info and tips!  i think i've seen that on dano's site, but i'll be sure to revisit it!

[Meanderthal]

 Yer on the right track.

Yes to your questions. Although I start at the input and work through to the out personally. You'll find it to be a kind of puzzle, as MarkM would say, and get a charge ottta the thing when ya fire it up and it works all unsoldered and hangin' in the air....

A side note- if ya want, you can always get a rat shak experimentor's pcb which is an ordinary breadboard layout (as opposed to the Cadillac in the photo. Nice one! For yours it would be only one section of 3...) and just transfer yer breadboard layout to the pcb.

But, creating your own pcb layout is the more noble path to take. I only suggested the rat shak pcb to point out a layout possibility I never see mentioned. It's always perf, vero, or RTS PCB, yet there's another option.

[Barcode80]

jlullo, if the circuit is neg ground, you need the red to be positive. that is the hot voltage. the common is the ground. if you use the -15 supply, the common becomes a positive ground because you are using negative hot side.

[jlullo]

meanderthal,
awesome!  i think i just caught my own mistake, though.. since it is a negative ground circuit, that would mean that i'd use th *positive* supply, right?  

i might try it both ways and see what seems most logical to me- starting at the input vs the op amp.

you're the man, man

[jlullo]

barcode,
got it!  thank you   that makes a lot more sense after i thought about it logically... because if the ground was negative, the power would have to be positive

haha

[jlullo]

one more quick question before i start doing this baby up...

looking at the schematic, if i didn't have the parts list right in front of me (which i do), how would i know if the pots were lin or log?  also, how do i figure out what connection = which lug?

[Meanderthal]

i think i just caught my own mistake, though.. since it is a negative ground circuit, that would mean that i'd use th *positive* supply, right? 

Hmmm... Yes. What Barcode80 said... Although it ain't a mistake if ya catch it before ya do it.

So, I take it the pots can lower the voltage? Might be a good idea to set it fer 9v for obvious reasons.

I like the +/- 15v power supply on that thing! You'll find that very useful if you ever get into synth circuits!

[Meanderthal]

 Generally, a tone is linear, a volume log, and a drive either, sometimes(as in the D+) even reverse log. That should be specified in the schematic, but sometimes is not. A lin. will always work, but the sweep might not be smooth.

As far as the lugs, usually on a schematic the pots are shown vertical(not always) and from top to bottom- 3, 2, 1. Obviously, 2 is always the middle, so if worst comes to worst and ya get it backwards(the knob works backwards) you can always just mirror the connections and all is as it should be.

[jlullo]

thanks buddy.... i'll do my best to get this all up on the breadboard and report back afterwards!

[jlullo]

hey guys.  i'm breadboarding this up right now, and have one quick question.  how can you tell capacitor polarity on tonepad's schematics?  it isn't marked at all

[jlullo]

nevermind.  i figured this out.. they were NP mylar caps.

one more quick question- i need a 51 pf cap. i have a mylar film cap value pack from futurlec, and there are two values that i think would work- 4700pf and 5600pf.  do i just drop the zeroes off of these, or is 4700pf completely different than 47pf?

[dxm1]

one more quick question- i need a 51 pf cap. i have a mylar film cap value pack from futurlec, and there are two values that i think would work- 4700pf and 5600pf.  do i just drop the zeroes off of these, or is 4700pf completely different than 47pf?

Different - one has 47 of those little pFs running around inside, the other has 4,700. A 47pf will usually work OK in place of a 51pF, though (close enough).

[jlullo]

okay thank you dxm1!  that's what i figured

[jlullo]

alright fellas.... here it is:


does this look right to you guys?  it could use a little tightening up, but i don't want to bring it in too close before i know that there aren't many mistakes...

the blue traces are Vb
red is +9V
grey is ground

i'd like to eliminate the jumper, so i'm thinking tomorrow i might play around with wrapping Vb around the left side of the layout, and bringing it around top.

[jlullo]

alright.... slightly cleaned up layout.  i got Vb connected without a jumper, now had to move a jumper connecting IC1 to IC6



I hate jumpers!! any suggestions?  do these connections look ok?

[jlullo]

should i have put this in a different post?

[calculating_infinity]

lol Jonathan maybe?  I have been keeping up, good job man.  I can't help you cause yeah I'm still a novice but I believe it may be better to make a new post asking for people to confirm your layout.  Don't forget to post the schem you used.     I am going to try to make my first layout this weekend or the next and try to post it up.  Good luck!

-Jonathan