3com Officeconnect 10/100 8 Port Hub

[willawake]

Some of my hubs and switches are hissing (Sort of air sound not screaming). Since they are fanless I was curious. Opened one up and saw :



The two caps in the foreground are Gloria 6.3V 1500mf which appear to have swelling at the top and some slight discharge. :cry:

The caps in the background are GAE LESR 50V 1000mf. The small caps are Wendel 47mf 16V. Those appear to be fine.

Apart from the visual indications and the hissing sound the hubs are operating fine. I have 4 of these units grrrrr, purchased Feb 2000. Probably will get 1 24 port professional switch instead as it is time for more upgrading (will have to do some rewiring though). Any recommendations?

[willawake]

Here is a link I found to similar problems with what looks like an older model of 3com hub. Having read the article I noted strange collision problems also on one of my hubs but not regular at all.

http://www.feistworks.com/ben/3comfix/

[kc8adu]

get out the soldering iron and replace those caps.
many smps units hiss/fizz when the caps are bad.
change them before it gets worse.

[mercyground]

My hp 10/100 8port died a similar death but i couldn't see any bad caps in it. Got seriously hot thou. Phoned HP and they RMA'd it for me. gotta love lifetime warrenties.

[willawake]

mercyground : I had some intel inbusiness hubs previously also. They started making a terrible fan sound due to a cheap small fan on one of the chips and then the external power supplies just went dead one by one. Got one power supply out of the junk pile recently and opened it but it had nice rubycon caps and no signs of cap failure anyway. It is a pity these critical items have problems like this. A lifetime warranty with HP..nice......but havent seen one of those here recently.

kc8adu : thanx for the info about the smps units. I am learning a lot from this forum. I am looking at a cisco 2950 24 port switch, time to stop buying soho products and I can really use some of the admin features. Will repair the hubs later and store them for backup units.

[willawake]

Finally I recapped with Panasonic FC. No more Gloria caps on this item.



works as well, nice.....

[gg1978]

Did recapping get rid of the "hissing"?? Looks like you have a pair of switchmode vreg's there, one is +3.3V, the other is -5V. Sometimes switchmode vregs have a "hiss" to them, usually in the inductors. Maybe that's what you were hearing?? Failing caps can certainly result in funny noises too.

[willawake]

Yeah the hissing is gone. I did some testing but I am getting some collisions, I dont remember it being like that. I will do some more because it may be due to NIC configurations. I dont have the same setups anymore. Like if i run it with intel pro1000mt cards it gets constant collisions but still transfers the data fine.

But if i connect to it with a 3com 100mb card and connect it to the network via a cisco switch i get minor but repeated collisions. Can send a large zip file back and forth with no corruption.

Thought i did a good job with the soldering though. I will try another (have 4 units to do) and see what happens.

[willawake]

turns out that it was a nic configuration issue or something, got it working fine now.

[willawake]

done 3 now and all working all these days in production fine. buying some time while i do the cabling to the new cisco 24 ports and also can be installed as backup system in case there is some problem with the cisco. Thank you badcaps.net.