How easy it it to ruin caps?

[deezymailmail]

I'm having the hardest time getting my Thing Modulator to work and burning up the caps is the only thing I can think of.  I feel like I've quadruple checked everything, resoldered everything multiple times, and still no luck.  I socketed the IC, so I wouldn't burn it up.  I know electros have +/- orientation, I did that right.  Once I finish my layout on DIY Layout Creator, I'll post it for review.  Has anybody built one of these?  It's from Tim Escobedo.

[earthtonesaudio]

Technically, polarized caps should never be reversed biased, even by signal.  However, most of us have used them for AC coupling for myriads of projects without trouble, so to me it sound like you have a wiring error, a bad IC, or a bad batch of caps.

[Cliff Schecht]

Technically, polarized caps should never be reversed biased, even by signal.  However, most of us have used them for AC coupling for myriads of projects without trouble, so to me it sound like you have a wiring error, a bad IC, or a bad batch of caps.

Electrtolytics can handle the short burst of negative bias from AC signals without problems. It's when you give them a DC voltage without any current limiting that they go "POP!".

[Wales]

Haven't built one of these but I find that I burn out the caps that connect to the wires going to a pot or something cause I do my off board wiring last and you pretty much have to solder those caps twice if the cap and wire are right next to each other on the board. (holy run on sentence Wales) I have since learned about a heat sink, you can clip it on the cap and it will absorb the heat rather than the cap absorbing the heat.

Its not like a heat sink in a computer or car amplifier, but its just a clip on pair of tweezers.

Maybe you already know this, but I would check caps that are close wires.

[biggy boy]

Its not like a heat sink in a computer or car amplifier, but its just a clip on pair of tweezers.

Maybe you already know this, but I would check caps that are close wires.

Roach clips used to keep the caps from being burned up.
as apposed to roach clips being used to keep your fingers from being burnt up.

[deezymailmail]

Alright, thanks guys.  I've rebuilt this thing in several ways and it just won't work, so I'm guessing it's the caps.  Either that, or I just don't fully understand grounding.  I feel like that's my only other weakness.  My first real build didn't pan out as well as I had hoped 

[R.G.]

Electrtolytics can handle the short burst of negative bias from AC signals without problems. It's when you give them a DC voltage without any current limiting that they go "POP!".

Actually, that should read "Electrtolytics can handle the short burst of negative bias from AC signals without an immediately obvious problem."

Persistent reversing with signal can still cause cumulative degradation. It depends on how much current flows in the reverse direction. Oxide "ungrowth" is just about proportional to current. Course, it tends to grow back when it's properly polarized, as long as the electrolyte in the cap can support the reaction. These days, the oxide forming bath is not the same as the sealed in electrolyte. They've become specialized.

But no, they're unlikely to "pop". They just go leaky and low capacitance.

[WLS]

... I have since learned about a heat sink, you can clip it on the cap and it will absorb the heat rather than the cap absorbing the heat...

I maybe wrong but I never really worried about too much heat in relationship to capacitors and resistors. The ones I clip to disapate heat are the diodes and rectifiiers. They seam to be the most sensitive.



Bill

[Cliff Schecht]

Electrtolytics can handle the short burst of negative bias from AC signals without problems. It's when you give them a DC voltage without any current limiting that they go "POP!".

Actually, that should read "Electrtolytics can handle the short burst of negative bias from AC signals without an immediately obvious problem."

Persistent reversing with signal can still cause cumulative degradation. It depends on how much current flows in the reverse direction. Oxide "ungrowth" is just about proportional to current. Course, it tends to grow back when it's properly polarized, as long as the electrolyte in the cap can support the reaction. These days, the oxide forming bath is not the same as the sealed in electrolyte. They've become specialized.

But no, they're unlikely to "pop". They just go leaky and low capacitance.

You're definitely right about elecrolytics being effected over time by negative biasing. The big deal in this case is how hard you are reverse biasing the device and for how long. Low peak-to-peak are typically very low power however and hence low current, so these won't do much damage. It's the constant DC reverse bias that really makes things all sticky and gooey .