How to clean relay contacts?

[Andrey]

Hello All,

I am dealing with a bunch of relays that have burnt out contacts: Mechanics
works fine but contacts measure 3 - 15 Ohms between them instead of zero. I
opened several - the contact pads turned dark gray, almost black. It is not
coal, still looks like metal surface. The dark surface is very thin, several
passes of sandpaper clean it and relay works fine after that.

I wonder if there is a way to clean the contacts without opening relays (the
relays are sealed, opening destroys them)

Appreciate any wisdom

Andrey

PS: the relays are used to switch RF power at 2 - 30 MHz

 

[Rheilly Phoull]

"Andrey" <a8421@intergate.bc.ca> wrote in message
news:1103cq0615ejj66@corp.supernews.com...

Hello All,

I am dealing with a bunch of relays that have burnt out contacts:
Mechanics
works fine but contacts measure 3 - 15 Ohms between them instead of zero.
I
opened several - the contact pads turned dark gray, almost black. It is
not
coal, still looks like metal surface. The dark surface is very thin,
several
passes of sandpaper clean it and relay works fine after that.

I wonder if there is a way to clean the contacts without opening relays
(the
relays are sealed, opening destroys them)

Appreciate any wisdom

Andrey

PS: the relays are used to switch RF power at 2 - 30 MHz

Could also be oxidisation if they dont have some 'wetting' current which is
not easy clean off without physically touching them. Are they located in
good conditions ?

--
Regards ..... Rheilly Phoull

 

[Guy Macon]

Tim Wescott wrote:

If the system is designed to switch with power on then it'll take a
special relay to not break down under that treatment; I don't even know
if such a thing exists at all.

Indeed it does.

http://relays.tycoelectronics.com/kilovac/hvintro/vacuum.stm
http://relays.tycoelectronics.com/kilovac/power/default.stm

 

[John Woodgate]

I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog
DOTyou.knowwhat> wrote (in <70h601pbv39oqtmb0pnbgqm53gnkt73v90@4ax.com&gt
about 'How to clean relay contacts?', on Fri, 4 Feb 2005:

Some of us distinguish between the two based on the construction.

What are the constructional differences? I have relays that look like
small contactors. Or....
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Keith Williams]

In article <42030620.825D5A5B@att.net>, NoSpam@att.net says...

Tim Wescott wrote:
(snip)
If the system is designed to switch with power on then it'll take a
special relay to not break down under that treatment; I don't even know
if such a thing exists at all.
(snip)
Tim Wescott


Oh sure; ever hear of "contactor"? That's a 25-cent word for "relay
with whacking great contacts".

A "contactor" is a "relay" that has contacts that you won't want to get
body part between. ;-)

--
Keith

 

[Rich Grise]

On Fri, 04 Feb 2005 10:36:17 +0000, John Woodgate wrote:

I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog
DOTyou.knowwhat> wrote (in <70h601pbv39oqtmb0pnbgqm53gnkt73v90@4ax.com&gt
about 'How to clean relay contacts?', on Fri, 4 Feb 2005:

Some of us distinguish between the two based on the construction.

What are the constructional differences? I have relays that look like
small contactors. Or....

I've seen contactors with a separate "start" contact, that then use one of
their own contacts to hold them closed - that way if there's a short power
outage, you have to restart all of the motors in the factory by hand.

Presumably, it prevents equipment damaging itself, like if the controller
is resetting or it's some process that if it's interrupted, has to be
reinitialized and restarted, that sort of thing.

Thanks,
Rcih