[sdiy] There is no fun analogue chips anymore!

[Barry Klein]

Many designers don't realize that effective capacitance drops often 50% with DC across multilayer type ceramics - and this varies between manufacturers and voltage ratings.
I hadn't come across any that got worse over time though.  Any background on this - a particular vendor?

Barry


-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Gordon JC Pearce
Sent: Thursday, June 28, 2012 12:26 PM
To: sdiy diy
Subject: Re: [sdiy] There is no fun analogue chips anymore!

On 28/06/12 20:16, Pete Hartman wrote:
> So I have displayed my ignorance publicly again :-)
>
> Thanks for the pointers.  Glad to see it's not as complicated as I had 
> thought from some long past exposure to things like "flowing solder 
> with a toaster oven".
>
> Pete

http://www.gjcp.net/~gordonjcp/capacitor.jpg

That was taken with a cheapy USB microscope.  It's an 0.1μF ceramic capacitor in a Kenwood HT, part of the mic preamp, and like all little ceramic caps prone to going leaky if there's a DC voltage across them - like, uh, the preamp bias voltage.  The replacement in the picture was hand-soldered, cleaned up with some flux cleaner, and you'd hardly tell it had been touched.  I used a fairly pointy soldering iron tip and some tweezers that I'd reshaped a little to be better at picking up tiny grain-of-sugar components.  I didn't use the USB microscope because it is too "laggy" to update.

Now, I don't need glasses, but I'm 38 and I can tell my eyesight isn't as sharp as it was ten years ago ;-)

It's not that hard...

--
Gordonjcp MM0YEQ


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