Badcaps Forums

Badcaps Forums (https://www.badcaps.net/forum/index.php)
-   Troubleshooting Power Supplies and Power Supply Design (https://www.badcaps.net/forum/forumdisplay.php?f=32)
-   -   Cisco pix 506 fw psu (https://www.badcaps.net/forum/showthread.php?t=50205)

Shodan486 11-09-2015 10:31 AM

Cisco pix 506 fw psu
 
3 Attachment(s)
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 :D ), 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 11-09-2015 12:26 PM

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 11-10-2015 09:06 AM

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 11-10-2015 09:55 AM

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 11-10-2015 02:13 PM

Re: Cisco pix 506 fw psu
 
What's the original cap?

Shodan486 11-10-2015 03:17 PM

Re: Cisco pix 506 fw psu
 
25V 47uf Rubycon, which should be one of the best. Looking for a spare one now...

stj 11-10-2015 03:24 PM

Re: Cisco pix 506 fw psu
 
what series of rubycon?

Shodan486 11-10-2015 03:36 PM

Re: Cisco pix 506 fw psu
 
''YXF'' , those should be low impendance @ 105C

stj 11-10-2015 03:46 PM

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 11-10-2015 09:25 PM

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 11-10-2015 10:03 PM

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 11-12-2015 08:52 AM

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 11-12-2015 09:52 AM

Re: Cisco pix 506 fw psu
 
capacitor lifespan is directly related to heat because the liquid in it can dry out or crystalise.

Behemot 11-12-2015 09:58 AM

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 11-12-2015 10:39 AM

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 :D . 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 11-12-2015 10:43 AM

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 12-04-2015 02:54 PM

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 12-04-2015 04:33 PM

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 12-04-2015 05:08 PM

Re: Cisco pix 506 fw psu
 
Measured it outta circuit - no problems at all, a slightly increased impendance only.

Behemot 12-13-2015 04:51 AM

Re: Cisco pix 506 fw psu
 
Quote:

Originally Posted by Shodan486 (Post 606460)
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 :D . 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.


All times are GMT -6. The time now is 07:04 AM.

Powered by vBulletin ®
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.