Is there a reasonable way to measure surface mount cap values, in-circuit?

[Praying_V]

I was tracing out a schematic of *something*, but the tiny surface mount caps aren't labeled in any way... Is it hopeless?  There's about 20 such caps.  PS, I don't have a signal generator. 

[grapefruit]

You have to remove them. Personally, if I were tracing a PCB I wouldn't worry about the value of the caps. Once you've got the schematic drawn you should be able to figure out what value the caps should be. If you're doubtful on some just remove and measure those ones...

Stew.

[Praying_V]

There are two particular filters that I want to know the values in.  Unfortunately its not my pedal, so I really shouldn't go desoldering things...  Oh well!

[Ice-9]

Hi, What is the pedal in question , maybe someone here has a schematic for it or a link to it.

[Praying_V]

I'm pretty sure there's no schematic, its a pretty new pedal...  I don't think we can discuss things like that here.

[grapefruit]

You could still "suck it and see".

I had to repair a bassballs before the schematic was available on the Internet. IIRC power had been hooked up reverse polarity. Among the blown bits was an electro cap that there was no way of getting the value of. I traced the circuit and drew the schematic, guessed a value for the cap (envelope filter smoothing cap) and tweaked it until it worked best. Years later when I came across the schematic it had the same value I selected!!

You might learn more that way too


Cheers,
Stew.

[ayayay!]

http://www.advancedevices.com/products_tw.htm

[puretube]

Keyword: "In Situ"...

[R.G.]

I'm pretty sure there's no schematic, its a pretty new pedal...  I don't think we can discuss things like that here.

Hey, here's a thought. Did you ever think about where network schematics come from?

[Praying_V]

Network schematics?

[petemoore]

  People reverse engineer, I've seen it done from just post pictured of top and bottom of board.
  Your parts seem aweful small and hard to work with I think.
  Not sure what the goal is.
  Short answer: No.
  Long answer is still probably no [not in circuit with perfect reliability...I assume here...], but they should block DC and you can tell if that's happening..usually or always.

[Processaurus]

odd, desperate idea, if you aren't going to desolder the caps and measure them (not really that bad, and the simplest approach...), you could alternatively build the circuit and sub in caps until you got the same capacitance measured on each cap in-circuit on the breadboard as the ones in the pedal circuit.

[slacker]

I'm pretty sure there's no schematic, its a pretty new pedal...  I don't think we can discuss things like that here.

We can discuss whatever we like, if you tell us what pedal it is someone might be able to hook you up with a schematic. You're not allowed to post schematics for a very small number of manufacturers pedals as explained here anything else is fair game 

[Praying_V]

Its an MXR El Grande Bass Fuzz.  Its nothing worth cloning, but I'm just curious about the values they've chosen to adapt a fuzz for bass use.

[Harold]

Its an MXR El Grande Bass Fuzz.  Its nothing worth cloning, but I'm just curious about the values they've chosen to adapt a fuzz for bass use.

Any luck with tracing the El Grande yet? Or have you given up on it?

As usual, the MXR products are way overpriced here in the Netherlands, so I'd like to clone and thoroughly test one before buying it...

[earthtonesaudio]

This:

http://www.advancedevices.com/products_tw.htm

Can do this:

Keyword: "In Situ"...

...but it's quite expensive.