Cisco pix 506 fw psu

[Shodan486]

Hey there !

Been a while since I visited this lovely site ! Hope everything's alright, saw some red notification up there, hope the admin & badcaps store ain't in no trouble !!!

So I wanted to start my cisco trainings and stuff, hooked up my FW mentioned above to the PSU, worked one day. Did the same thing the next day, nothing. Dead. Tried the spare one - worked.

Disassembled, investigated. The PSU looks OK, no burnt spots or parts. Providing the picture. There is one indication of a failure, fortunately. The place with caps and the regulator is ''ticking'' (not like a bomb ), producing the sound twice per second. I think it is the regulator, but that's why I'm writing in here - to ask you guys if I'm right. Providing pictures.

Appreciate the help in advance !

[stj]

Re: Cisco pix 506 fw psu

ticking is either a shorted output, or a bad startup capacitor.

change the small cap c4 next to the control chip

and check the diodes on the other side of the transformer

[Shodan486]

Re: Cisco pix 506 fw psu

Thanks for the advice !!

The diodes show 470 and 778 values on the diode test. The regulators (the ones attached to the heatsink) show values between 400 - 650 when you measure the leads, but one of them shows 600 on one leg and beeps (short) on the other leg - which to me (since I'm an total amateur) is not a good sound. But I believe that removing the parts and measuring them outside the circuit is more reliable, thus will remove them and measure.

Should I continue replacing the C4 cap if this has been discovered?

[stj]

Re: Cisco pix 506 fw psu

it will last longer if you do, even f it's not the problem.
make sure you use a low impedence one like a panasonic FC/M/R or a rubycon ZL for example

[Behemot]

Re: Cisco pix 506 fw psu

What's the original cap?

[Shodan486]

Re: Cisco pix 506 fw psu

25V 47uf Rubycon, which should be one of the best. Looking for a spare one now...

[stj]

Re: Cisco pix 506 fw psu

what series of rubycon?

[Shodan486]

Re: Cisco pix 506 fw psu

''YXF'' , those should be low impendance @ 105C

[stj]

Re: Cisco pix 506 fw psu

yxf is entry level low, and it's obsolyte - think the lowest you can buy now is yxg
so it's pretty old.

[Behemot]

Re: Cisco pix 506 fw psu

But it's oil electrolyte if I am not mistaken so it should really work for ages. If you have a meter, try measuring it, if not, well than it's worth trying to replace it…

[stj]

Re: Cisco pix 506 fw psu

yxf are good performers - specially in audio gear.
but they do fail if they are near heatsinks, i'v seen a few go.

[Shodan486]

Re: Cisco pix 506 fw psu

Why would they fail near heatsinks? Anyways, still haven't found a replacement one, I'm gonna hit the electro shop we have in the town tomorrow.

[stj]

Re: Cisco pix 506 fw psu

capacitor lifespan is directly related to heat because the liquid in it can dry out or crystalise.

[Behemot]

Re: Cisco pix 506 fw psu

More like chemically react and create compounds which are solid, not liquid. Drying may be the case of water-based electrolytes, but it is not like there is water floating inside, it's chemically bonded too.

[Shodan486]

Re: Cisco pix 506 fw psu

Sure it's the heat that usually kills the caps, but I thought that it would be something else since you said you've seen a few go . Nevermind and thanks anyways stj, because Behemot here stated an interesting fact : " Create compounds which are solind, not liquid " . Behemot can you elaborate, please?

Meanwhile I'm gonna dig through my junk board to see if I can find that cap, motherboards have similar ones near the audio chip usually.

[stj]

Re: Cisco pix 506 fw psu

i doubt a motherboard would have low esr near the audio chip.

you can probably use 100uf if it's easier to find.

[Shodan486]

Re: Cisco pix 506 fw psu

Replacing the mentioned capacitor did no help. I've acquired all the other capacitors as well, I'll try to replace them all.

[goodpsusearch]

Re: Cisco pix 506 fw psu

Never seen a failed YXF in my life. If you ask me they are as reliable as caps can get.

[Shodan486]

Re: Cisco pix 506 fw psu

Measured it outta circuit - no problems at all, a slightly increased impendance only.

[Behemot]

Re: Cisco pix 506 fw psu

Sure it's the heat that usually kills the caps, but I thought that it would be something else since you said you've seen a few go . Nevermind and thanks anyways stj, because Behemot here stated an interesting fact : " Create compounds which are solind, not liquid " . Behemot can you elaborate, please? .

For example salts and other compounds. The electrolyte and the foils react and loose their function. Capacitance descreases, ESR increases.