"Unapproved" input filtering

[momaka]

Re: "Unapproved" input filtering

However, I can't think of an instance where I've ever seen an X or Y cap fail before - even on cheap junk PSUs.

I saw a thread once on here about fixing up some old computer. Basically, as soon as the OP plugged it in, there was smoke and the PSU eithe blew a fuse or tripped his house breaker (this is all IIRC, so I'm not exactly too sure on the details). When he posted pictures, we noted that it was an X cap that overheated and burned itself to death right on the input. I also don't remember if that X cap was behind a fuse or not. It was a legit X cap nonetheless.

So yeah, while rare, it does happen. That mentioned, I need to update my grounding thread whenever I get my internet back (or whenever I go back in the library). I changed one of the 2-prong plugs in my rental place to a 3-pong and plugged in all of my gear. So far, all is okay .

I've found ASUS to be the picky ones.

So I guess the conclusion we can draw here is - stay away from ASUS and Intel/Foxconn motherboards. I'll take MSI and Gigabyte any day. Also, Jetway boards are really nice once you get rid of those Sacon/Evercon/GSC caps.

[ben7]

Re: "Unapproved" input filtering

I saw a thread once on here about fixing up some old computer. Basically, as soon as the OP plugged it in, there was smoke and the PSU eithe blew a fuse or tripped his house breaker (this is all IIRC, so I'm not exactly too sure on the details). When he posted pictures, we noted that it was an X cap that overheated and burned itself to death right on the input. I also don't remember if that X cap was behind a fuse or not. It was a legit X cap nonetheless.

Some old Rifa capacitors failed like this, causing smoke. They are found in some vintage comp's, I'm sure you could find an example with a quick google search... at least I think they are supposed to be X caps.

You're welcome! Just remember, at the end of the day, after you learn anything new, you're no longer a "noob."




There was a time when you could bond to a cold water pipe, since the incoming neutral of the drop was supposed to be tied to the CWP with the GEC, even if the receps were ungrounded. It was common for washing machines to include their own ground/bond wire and clamp for just this purpose.

....snip.....

Didn't you know power supplies can grow legs? Maybe a few will follow you home, where they'll be serviced properly...

Haha, I was thinking, hm, I should add some links to MH's stuff .... you beat me to it! xD
He has a great (kind of scary) article about a bad neutral connection...
http://www.mikeholt.com/mojonewsarch...d~20040506.php
(Yes, a long read, but well worth it IMHO)

And LOL at the power supply legs joke

I actually probably have some of these questionable Y caps sitting around, I wonder if I can get them to fail shorted using some high voltage, and also test some proper safety rated ones at the same voltage(s)

Edit: Ugh, just remembered, a while back I missed the opportunity to get a HIPOT tester....

[Pentium4]

Re: "Unapproved" input filtering

You're welcome! Just remember, at the end of the day, after you learn anything new, you're no longer a "noob."

Very true

To debunk "path of least resistance," here's a neat experiment. You'll need:

A plugstrip
A lamp & bulb- CFL, LED, or incandescent, anything from 4 to 100W.
Cord connected, high power appliance- vacuum cleaner, toaster, heater, etc.

Connect plugstrip to power and connect lamp. Lamp comes on, right? Okay, now plug the vacuum in and turn it on. Does electricity really take the path of least resistance? The answer should be obvious, as both the lamp (high resistance) and vacuum (low resistance) are now running at the same time, directly in parallel with each other.

Hope that was fun.

Definitely going to try that later

Use it to your advantage!

The ones who'll never learn? Let them break everything, then "amuse" yourself with their excuses of "Why you want so much to fix what I broke." They get uniblue and other trash on their computer, then think you, or your company's price is "unfair?" Walk away...

People amaze me sometimes! They get upset when their computer that's covered in dust, running 24/7 in a hot ambient temperature and never do routine maintenance, are outraged when something fails after 3 or 4 years. And when offered a recapped "refurbished" power supply for $40, or a "brand new" one for $59 (filled with chinese caps) 9 out of 10 times they'll take the new one, even after I explain to them what I did. Their response is usually "But it's been broken before!" Arrgghhh.

Oh sure, it'll be about how "I can't be w/o a computer," or "I haven't backed anything up," as if you should feel sorry. Well, you sure as hell didn't put uniBULL on there, did ya?

Yep, you sure know the game don't ya "I can't be down more than an hour, and I have a tight budget!" So since we're good with computers, we're automatically all knowing, all powerful beings that just wave our magic wands or use our black magic to immediately fix said problem?

Give yourself an easy way out- tell 'em to "get vistafied." Those round corners and "special interface" are perfect snares for "catching sheep."

Too funny, man!

Usually when customers are upset at our "24-48 hour turnaround" they'll "shop around" Seattle and then happily come running back when they find out our competition averages 1 week turn around

[c_hegge]

Re: "Unapproved" input filtering

And when offered a recapped "refurbished" power supply for $40, or a "brand new" one for $59 (filled with chinese caps) 9 out of 10 times they'll take the new one, even after I explain to them what I did. Their response is usually "But it's been broken before!" Arrgghhh.

Yup. In the minds of the computer-illiterate public (and even many so-called "techs"), there is absolutely no way in the world that any product which has seen any use could possibly be anywhere near as reliable or trustworthy as a brand new product - even if the used product is built far better in every way imaginable.

[momaka]

Re: "Unapproved" input filtering

Yup. In the minds of the computer-illiterate public (and even many so-called "techs"), there is absolutely no way in the world that any product which has seen any use could possibly be anywhere near as reliable or trustworthy as a brand new product

Yeah, whever I suggest someone buy some used peice of gear, they look at me as if I suggested to them to buy a used diaper.
Most people are like that, though, and it's just unavoidable with the way things are priced these days, where buying new costs almost the same as buying something old.

[goodpsusearch]

Re: "Unapproved" input filtering

Well, I usually get them to buy a used recapped, fan modded and fan oiled psu from me rather than a new Hantol 550W with fake ppfc that will be at any load out of spec :P

[kc8adu]

Re: "Unapproved" input filtering

the gold/yellow rifa tend to blow up and smoke grandly.
i rebuilt some old power one open frame power supplys a while back and one blew up during burn in.
stunk the whole shop up!

As for the whole unapproved filtering issue, I agree it's poor practice (and possibly even illegal in some countries) to use unapproved components. However, I can't think of an instance where I've ever seen an X or Y cap fail before - even on cheap junk PSUs.

[Guillermo]

Help

Hi i have a bestec ATC-300-12z power supply, and the power went off and then back on, and it blow the varistor, and i put in an other one and it dos not work. what should i do???

[Behemot]

Re: "Unapproved" input filtering

Maybe fuse blown as well. After that test with incandescent light bulb in series.

[Guillermo]

Re: "Unapproved" input filtering

Can you tell me the location of the fuse i cant find it i have looked over and over

[Behemot]

Re: "Unapproved" input filtering

Usually it is just right next where the AC wiring is connected to the PSU board…

[Guillermo]

Re: "Unapproved" input filtering

Thanks i found it and it works you have been very helpfull

[kaboom]

Re: "Unapproved" input filtering

the gold/yellow rifa tend to blow up and smoke grandly.
i rebuilt some old power one open frame power supplys a while back and one blew up during burn in.
stunk the whole shop up!

Like burning cookies/marshmellows.

Working on (finished actually) someone's Yamaha A-1060. These have the same triac modulated power transformer that Carver amps do, hence the same type of AC line filter.

The X cap either leaked real bad back around Christmas time- owner was ready to call fire dept after not being able to find source of the smell. This isn't always enough to blow the fuse; not even 1-2A, while the X cap explodes.

Unit was in a cabinet with cooling fans, which dispersed the smoke/smell. If not for them, there would've been an obvious smoke cloud which would've given it away. This unit still smelled after several months of sitting around. Had to wash main amp and input boards. Flux/dirt and electrolyte from old caps.

Those Rifas used their expoxy molding as the case, which cracked and let moisture in, destroying the cap.

I remember some older Apple PSUs "blew up" some years/threads ago on BCN. Exploding Rifas- how we've been spoiled with modern components.

[japlytic]

Re: "Unapproved" input filtering

Those Rifas used their expoxy molding as the case, which cracked and let moisture in, destroying the cap.

I remember some older Apple PSUs "blew up" some years/threads ago on BCN. Exploding Rifas- how we've been spoiled with modern components.

This also includes Miniprint units, made by Rifa and AEE (Australia).
The same goes for clear epoxy encapsulated units in my experience - an 80s GoldStar frequency counter (with a blown AC fuse) had a clear epoxy Rifa unit which failed, and in an AC power conditioner, a Wima clear epoxy unit failed and blew the fuse in the unit.
One other thing: in a powerline intercom unit from RadioShack I repaired for a client, it had bad Rifa X-class (again, clear epoxy) which coupled the RF to the AC mains.

[eccerr0r]

Re: "Unapproved" input filtering

Speaking about those RIFAs, supposedly there's a year they stopped being "bad"... or not?

Have to assume that any with a cracked case are bad and need replacement... I have a piece of 1988-1989 equipment that has a cracked RIFA so unless they used NOS, it was still an issue then?

[kaboom]

Re: "Unapproved" input filtering

Have to assume that any with a cracked case are bad and need replacement... I have a piece of 1988-1989 equipment that has a cracked RIFA so unless they used NOS, it was still an issue then?

No. They'll be bad after time, even if power was never applied.

That's almost as bad as audiophools selling used paper/wax caps on ebay, under the guise of "improving" the sound in old tube amps.

Those 6L6s will "sound" real good when DC from the previous stage biases the grid positive, and they redplate. The output (and power?) transformer will also "sound good" after a while- "sounds" like money!

You need a "cased" safety cap, something that does not use just the epoxy as the case. Got one of those Rifas for display purposes. Has the cracks but didn't blow up when I pulled it years ago. Makes an excellent "this is why we don't use these anymore" presentation- visual and immediate.

[stj]

Re: "Unapproved" input filtering

those rifa's were water-clear when new - once they yellow you should bin them.
i can probably get you several hundred boxed "new" ones from the 80's that are all yellowed and cracked if you want to "out" them to fools on ebay!

[eccerr0r]

Re: "Unapproved" input filtering

No. They'll be bad after time, even if power was never applied.

Of course, that's what I meant, NOS does not mean immunity from cracking. I don't know how much of, or if Tek had a whole stockpile of the bad RIFAs and kept using them, and if they did I should expect the same failures if they were used in 1980 even if RIFA changed formulations.

But I can't tell what code the RIFAs Tek used, as far as I can tell they were indeed from the batch of bad ones (is there a date code? Unfortunately I would have to pull the PSU to be able to look at it carefully, but it *is* cracked and I should replace it, regardless.). Again it would be nice to know when RIFA changed their formulation to one that won't crack.

There's them RIFAs



Bad RIFAs since early 1980s, why did Tek still use them in 1988?

[stj]

Re: "Unapproved" input filtering

it's not a bad batch, it's a bad design.

dont use the clear ones - simple as that.

boxed and potted only!

[eccerr0r]

Re: "Unapproved" input filtering

That would be a good rule of thumb I guess. But I thought RIFA was still making the clear pots, why would they still be making them if they are known bad? I'd imagine they should have fixed the problem else they would not still be in business... or perhaps these clear ones are NOS?

Let's buy clear RIFAs from Digikey!