Layout tips please...

[3nity]

bump.

 

[12afael]

maybe you want to add a pair of polyester caps in parallel to c3, c4.

 

[keefaz]

You may want C1 & C2 connected directly at XLR input, not on PCB (not sure if you did plan that already)
But I am not sure what is the theory behind this, I always connect XLR input pin 1 directly to chassis for my part, and I haven't RF problem, maybe my environment is sane ?

 

[Mendelt]

Where did the two 2k2 resistors go?
Pin 2 and 3 of the ina207 are floating now.

 

[3nity]

oh my bad you're right.

 

[dale116dot7]

[quote author="Infernal_Death"]Sorry if it's already said but you should avoid 90 degree turn traces. I am not experienced in drawing layouts but i remember to read that you should avoid them. Maybe some of the more experienced here can tell you why.
[/quote]

Etchant tends to go underneath the resist a bit, creating a thinning of the trace as you go towards the substrate. In an acute corner, this is exaggerated, and can cause a severe thinning of the trace. They call that 'acid trapping' but the etchant really is usually ammonium chloride for commercial production and ammonium persulphate or ferric chloride for DIY work. In addition, right angles are bad for both RF immunity and radiation.

Commercial PC boards have no problem with 0.006" trace widths and spaces these days, but if I'm doing a home-etch, I like to use a minimum of 0.012" trace but usually 0.018" or 0.020", but I use litho film to make artwork so I think I can go pretty thin on trace widths and get away with it.

I also like to copper-fill because that really makes the etchant last longer, and seems to make the etch go smoother, at least I find that it does.

-Dale

 

[Ptownkid]

[quote author="dale116dot7"]I also like to copper-fill because that really makes the etchant last longer, and seems to make the etch go smoother, at least I find that it does.
[/quote]

agreed

 

[3nity]

Question: how do we build ground areas????

 

[mwkeene]

If you put a ground pour on the bottom layer and signals on the top it may help you to clean up your routing a little as well. Obviously you want your ground on a nice wide pour to avoid ground shifts (although it is more of a worry when you are driving amps to ground instead of the smaller signals you are dealing with here). The decoupling caps help too. The idea with all of this is to avoid long skinny lines. Short and fat is better. You could definitely pack stuff in tighter than you have if you utilize bottom and top for traces/pours. This will help you keep your routes short. It also helps some times to sketch what you think the component placement should be on a piece of paper (while looking at the schematic). A rough sketch done before hand is a lot easier to modify than a half routed layout.

A few extra thoughts:
-Keep spacing between routes at or greater than .010". This is a conservative rating, as it has been a PCB industry standard for more than 10 years now.
-Keep copper .020" away from edges.

 

[Samuel Groner]

Perhaps I wasn't clear in my statement about the importance of the schematic--at least I can't read a bit in the one you showed. The schematic you copied from the datasheet is actually nicely drawn, it's just not the one you used to make the PCB which makes it pretty pointless to show.

The 330 ohm resistors are at the wrong place and it should be only one.

I would not join input and output pin 1--actually for the output you just need one pin if you don't want a (impedance) balanced output.

Noninverting input of the servo goes to audio ground not chassis ground. As I said, the chassis ground is just used for the RFI protection, nothing else.

Samuel

 

[3nity]

Samuel thanks for your advices. The last schematic i redrawn from the data sheet too. You're right cuz i had 2 different schematics maybe on the first layout...

Now take a deep breath....

Things to Fix:

330R you meant near to the 47uF before the Phantom Switch??

Disconnect Pin 1 of output.

Non inverting Input to Audio Ground instead of chassis??? help here please.

 

[Samuel Groner]

Sorry for my somewhat short comments, too much other work to do!

330R you meant near to the 47uF before the Phantom Switch?

As R103 (top left) in monte_generoso_r1.pdf. Note the grounding of the RFI protection caps C101 and C102 as well.

Noninverting input to audio ground instead of chassis?

Well, you asked that:

IC2 OPA137 pin 3 goes to ground or chassis?

Samuel

 

[3nity]

Allright!
Here i go again on my own........(singing)

This is the final schematic ( i think).
As stated in the first post the Pad/Phase/Phantom are Gobeetwen boards. So the 330R is on that board.



Now Revisioned Layout. note that the Red ltraces (top side) are just there to show you this but they will be wires. i see i made an error on C8 theres no pad for wire.

Updated schems:

Am i near a good completion??

 

[Samuel Groner]

I'd still suggest to clean up the schematic, as shown I can't read it without getting mad and you won't be able to design a good PCB. Use net labels for ground and supplies instead of direct connections. Signal flow is from left (inputs) to right (output) and top (positive supply) to bottom (negative supply). In addition to this I feel like it would be a cool idea to arrange the part numbers and values such that one is actually able to read them :wink: . R1 and R2 should get removed and I suggest to put R5 after R6.

What is R7 for? If it's meant to be an impedance balanced output as suggested by me it needs to go to pin 3 of the output, not pin 2...

You may want to orientate the diodes and polarised caps the same way on the PCB in order to aid visual inspection (ever seen an exploding lytic?).

If not already done, check that paper: PCBDesignTutorialRevA.pdf.

Samuel

 

[mwkeene]

Agreed. Inputs on left, outputs on right. Put your ground buss in the middle of the schematic. Put your +Vdc at the top, put -Vdc at the bottom. Should be much easier to understand, and thus lay out when looking at it that way. Think of it as current flowing down the page from a higher potential to a lower potential.
-Mike

 

[3nity]

Alright then...Back to work!!!
First thing: rearrange the schematics.

 

[3nity]

Again New Schematic Up.

Tell me what to change :sad: :wink:

 

[3nity]

does it makes sense now?

 

[Ptownkid]

How did you add jumper pads and connections on the board without them being present in the schematic?

 

[3nity]

well you choose them on the layout, even decide size diameter hole. jumpers were made by selecting the top layer traces. of course the layout will remain unconnected, like he does not recognize it. i don't know why.