Replacing old high-voltage electrolytic capacitor

[pol098]

Re: It's not just electrolytics that can go bad...

Thread revival for Googlers: re X2 mains-rated film capacitors losing capacitance there's an extremely interesting article at
[url]http://www.rutronik.com/index.php?id=1384&tx_ttnews%5Btt_news%5D=4259&cHash=783ebdb0d70d16e07f3464919ce30c1c[/url]
C-stability in X2 capacitors. I won't quote the entire article, but essentially it is as surmised on this site, repeated local flashovers which gradually reduce the area of metallisation. This is by design, a fault condition merely causes a tiny change in capacitance...

[pol098]

Re: It's not just electrolytics that can go bad...

In this and a previous thread
[url]https://www.badcaps.net/forum/showthread.php?t=18923&highlight=x-class[/url]
there's discussion of X-class and other capacitors losing capacitance, and a comment that it's rarely noticed as they're basically for EMI compliance and nobody notices (or cares).

They can be used for more critical purposes. I have a thermostat remote control (Digistat SCR) which failed; I discovered that a 680nF X-class capacitor losing capacitance is the prime culprit, with lots of these...

[pol098]

An interesting link on restoring, replacing, or repairing high-voltage capacitors in old equipment, e.g. multi-section 450V. Covers safe re-forming of existing capacitors, various replacement ideas, how to replace capacitor without changing the appearance of collectable equipment. If you pay, you could even get a capacitor rebuilt within the original can, until the one and only expert died.

[url]http://www.nmr.mgh.harvard.edu/~reese/electrolytics/[/url]https://An interesting link on resto...n 450V. Covers

[pol098]

Re: Capacitors and audio distortion

A note of caution: the work I'm citing, new to me, is 20 years old. The problems with, in particular, metallised film capacitors, varied from unit to unit, and were not characteristic of the type of construction; the best were very low-distortion. One would hope that manufacturers would have taken this on board, and that the method of connecting leads, or whatever other cause there was, has long been rectified, and distortion no longer a problem. On the other hand, you'd expect them to have got electrolytics right by now... It would be interesting...

[pol098]

Re: Capacitors and audio distortion

By the way, if anyone's interested the series of articles describe in great detail the design and construction of a 1kHz sinewave generator with distortion better than 1ppm (0.0001%). Circuit diagrams and PCBs for the generator and an associated very sharp notch filter included. Not a project for a spare evening, but perfectly feasible.

[pol098]

Re: Capacitors and audio distortion

"How did polycarbonate and polysulfone do?"
AFAIR polycarbonate did well, as did Polyphenylene Sulphide, if that's the same.

Some more from the article, which will answer some questions:

If you read the article (recommended), abbreviations much used are
Polyphenylene Sulphide - PPS
Polypropylene film - PP
Polyethylene Terephthalate - PET; metallised PET are discussed extensively
Polystyrene - PS

Foil/film capacitors that make their connections via extended...

[pol098]

Re: Capacitors and audio distortion

"... about audio signal coupling capacitors, not in other areas of amp circuits like the power supply."

Yes, for audio circuits not PSUs.

"Nothing new to discuss really..."

Not new as such in a 1992 article... But there are things there that surprised me. I had assumed that all wound capacitors were essentially equivalent; the article reported that film capacitors were a lot worse than other types, and also varied very much even within the same batch, with some having very low distortion,...

[pol098]

Bad capacitors in audio

I don't know if this is considered on topic - this site is called badcaps, but is mainly about electrolytic capacitors causing malfunction in power circuits due to high ESR. I didn't find any references to "Bateman", or any likely hits with "distortion", so maybe this has not been discussed, or is so familiar to everyone that it's never discussed.

In audio circuits capacitors of all sorts can produce distortion. Ceramic capacitors, as a class, have a particularly bad reputation, but this seems to be largely mythical. I don't...

[pol098]

Re: Cleaning Motherboards - ATTN SMOKERS!!

Interesting and long-running thread. I have a comment about the sheer time it takes things with nooks and crevices to dry naturally. A cordless DECT phone got dropped in dirty water, with battery in. I removed the battery and immersed it in tap water (all that was to hand), then took the back off without any further disassembly and soaked it in water that had been boiled and left to cool (to precipitate out the temporary hardness salts at least). I don't remember if I then used deionised water (it was a long time ago). I left it to dry...

[pol098]

Re: Dell Inspiron 1501 Win7 no toolbar preview or tooltips



That sounds reasonable. My suggestion involves the slightly mystical, but not totally impossible, concept of a conventional memory location whose contents remain stable when switched off, but are cleared when all power is removed - memory which is not formally non-volatile, but actually acts as battery-backed RAM....

[pol098]

Re: Dell Inspiron 1501 Win7 no toolbar preview or tooltips



Thanks for suggestions. I don't think the EC interaction is something I can sensibly check experimentally, but it makes sense; I think my speculation of a memory location that doesn't get reset is also conceivable (PCs used to have system information stored in RAM locations from, I think, 0x400, though I don't remember the details). BTW, over many years I have sometimes had problems with computers, and other electronic gear, which persisted across a restart, but cleared if the device was left unpowered for...

[pol098]

Re: Dell Inspiron 1501 Win7 no toolbar preview or tooltips



Thanks for considering this, there's been no useful discussion elsewhere of what happens. As you say, utilities not installed. But even if they were, NO software that runs at startup (or possible malware) makes sense of this to me. The problem persists even if the machine is switched off fully then switched on again (without removing battery), but goes away if machine is removed from power. These two actions should produce the same result.

I'd think it was my imagination, expect that there...

[pol098]

This is a very weird problem and workaround I'd like to find some explanation for. The workaround I'm using is OK, I'm not seeking a workaround but understanding (a proper, permanent, solution would be nice). It's probably not a capacitor problem as such. Dell Inspiron 1501 laptop, latest (last) BIOS. AMD Turion CPU. Windows 7/32 not officially supported but works fine in all other ways.

Under Win7/32 the machine is set up to display a preview of open programs by hovering over the toolbar icon. This is actually essential, as right-clicking the preview is the only way to access some...

[pol098]

Re: Asus



CPUs do, some or all chipsets do, but most motherboards don't. It's got to be supported by CPU, chipset, motherboard, and BIOS. I looked into it a fair bit recently, there was one Gigabyte motherboard, a whole lot of Asuses, and possibly one or more Biostars that even Biostar doesn't mention on their website. So for me it was Hobson's choice, never mind the capacitors, keep the data safe (I have suffered file corruption from bad memory, though very long ago, much more reliable now). BTW, going even further off-topic briefly, I saw some comments that 4GB...

[pol098]

Re: Asus

Hope this isn't too delayed a resurrection...

While not relevant to capacitors, there's one data-reliability issue which Asus are tops at. If you're as paranoid about data as I am and want ECC (error-correcting) RAM at non-server price, you're pretty much obliged to use an Asus motherboard and AMD processor. Nearly all Asuses, and nearly no others, fully support ECC (RAM websites often says they don't, and I've had a lot of correspondence correcting this, which they agree with and then ignore; the less expensive Intel boards and chipsets don't support ECC)....

[pol098]

Re: The Recapping FAQ

Long ago, before hearing of the idea of using a stainless steel sharp to clear the hole of solder, I worked out that a pointed wooden toothpick (or cocktail stick) would do the job as solder doesn't stick. It works fine, and I often still use it.

[pol098]

Re: Hello. Possible 8KNXP problem

Thanks for the comment. Frankly I wouldn't call 2003 capacitors which may be dying in 2011 victims of whatever plagues there may have been when they were made, but well-enduring veterans. Aluminium electrolytics often have a design lifetime of about 5,000 hours (~ 1 year), and this machine ran full-time until I implemented Wake on LAN a few years ago. Rather than replace the capacitors, which may or may not be the cause, I'm inclined to update motherboard, processor, and RAM. Thought I might just try buying an exact replacement motherboard for a...

[pol098]

Just joined, see I'm asked to post at least one message ASAP, this is it. Hello everyone.

No real questions. The reason I came here: I have an 8-year-old Gigabyte GA-8KNXP (rev 1) running off an 8-year old PSU that came with a case. Never given any trouble until recently. It's not a terribly slow machine for my purposes despite its age (2400MHz hypertheading Northwood, 4GB ECC RAM); mainly used as RAID file server with WinXP (patched to support software mirroring). A couple of weeks ago it began not to start when switched on from cold; never started first time, but eventually started...