identify this cap?

[cmbrow@wm.edu]

Hi, Folks,

First post here from a very long-time lurker and learner.

I'm upgrading the power supply for a Lampucera DAC mod, but I'm having trouble identifying the value of a cap in the power supply. There're six of them, and they come between the 1500uF 25v input capacitors (3) and the regulator ICs and between the the regulators and the 3300uF 35v output capacitors on the PS. I assuming that they're smoothing caps of some sort. The part number is 100-1826-0040, of which I assume only the 1826-0040 is relevant. Can any one tell me what these actually are. I've included a link to a similar PS. The chip in question is the green one at C11 on the board on the left.

TinyURL.com - shorten that long URL into a tiny URL

Don't know what I'd do without this site. It's been an inspiration and a challenge for the past few years.

TIA!

Chandos

[cmbrow@wm.edu]

OK,

After about a lifetime's worth of searching the web, I know that this is an Ero/Vishay series capacitor, possibly obsolete. What I can't determine from either the Vishay or the Ero data sheets are its values.

Does anyone know or can anyone make an educated guess?

Cheers!

CHandos

[Juergen Knoop]

have a closer look. The capacity value should be printed on it somewhere. Maybe as 0,1 J or 3,3n J on the top. Read this as 100n resp. 3.3n.

[!]

You might as well leave them alone, there's no real upgrade for them. Exact value isn't very important, just that replacements fit in the space /hole-spacing, are rated for high enough voltage. They're probably somewhere between 0.01uF and 1.0uF. Vishay MKT 370 might be equivalent. http://www.vishay.com/doc?28108

The better upgrade would be replacing the bridge rectifier with soft recovery diodes and replacing the regulator ICs with something higher performing. Both of these options may not fit on the PCB.

Also, you might want a different username if that's your email address.

[thaumaturge]

Based on proximity to the regulators, I'd say they were 0.1 - 1.0 uF local bypass caps. No need to update them as they aren't the type to dry out with age as an electrolytic probably would. If you still feel compelled to replace them, take a look at a spec sheet for the regulators and see what the mfg recomends for local bypass filtering. Personally I like to run both a 0.1 and a 1.0 uf right next to both sides of 3 pin regulators.
Doc

[benb]

If you really want to know, unsolder it (since you want to replace it anyway) and measure it. There are multimeters available with a reasonably accurate capacitance measuring function for around $20 USD.

It might or might NOT be good to replace older electrolytics with more modern, lower ESR ones - Bob Pease wrote in the book "Troubleshooting Analog Circuits" that some National regulator was designed to have a typical (for back then) electrolytic on its output, and that putting a ceramic or something else with a lower ESR may make it unstable.

[cmbrow@wm.edu]

Many thanks, all, for the very helpful suggestions! I've decided to leave them in place. I can't see any especially advantageous upgrade path, especially given potential complications. I'm simply going to replace the electrolytics and leave it at that.


Cheers!

Chandos