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Cleaning relays

James

James

Lord of the Erg\o/s
I think it is time to fettle my vintage Pioneer M-22. I noticed some minor drop-outs or fading from time to time on the right channel. It's not the preamp or sources, as the issue has not come up when I swap in a different power amp. I suspect it is the right channel relay, which is listed on the service manual as ASR-026. Not surprisingly, there are no replacements available from anywhere, and certainly not NOS items. It looks a lot like this example.

IMG_2169-551x551.JPG

Before I dive in, I thought I'd check if these can be opened up and the contacts cleaned with cleaner?

James
 
There may well be, but I'd like to preserve the originality of parts if possible.
 
These are excellent for cleaning relay contacts. They are effectively very slightly abrasive paper strips lightly loaded with cleaning/lubricant. You simply slide them between a closed contact and gently work them back and forward. They are much less abrasive than diamond spatulas and don’t take the tension out of the sprung contact mounting arms which can happen if you bend them back too far or for too long to clean the contacts. They were recommended to me by a relay manufacturer (very expensive multi-pole industrial relays used in gas turbine controls).

They won’t dress or shape badly pitted contacts but they are excellent at lifting light arcing and oxidisation with minimal damage to the contact surface.

https://uk.rs-online.com/web/p/electronics-cleaners/1015564/?sra=pstk
 
With care and attention you can normally get the plastic cover off (one above looks to have 1 lift tab on each side) - then easy to clean with a piece of emery paper and wash with alcohol
 
James said:
I'm not sure I understand what you mean.
Click to expand...
Power relays depend on a wetting current to keep the contact faces clean. Too much "dry" switching with no current flowing and the surface gets oxidised.
Switch a power resistor to a lowish supply voltage eg 5V at about 1A can blast the oxide off. This would need a 4R7 resistor on 5V or 10R off 12V
 
I remember the techs working on open switch contacts and relays in video games at my university.

The abrasive they used (push in, pull out) was ...

... photo copier paper.

You don't want to use "real" abrasives on plated contacts, since you WILL remove the plating.

BugBear
 
I used to work on juke boxes pin tables both electromechanical and electronic and I usually prised the cover off the relay and filed the contacts with a magneto file.

Signal relays it was often just dirt so a rub with paper soaked in contact cleaner would work.


Pete
 
If the contact surfaces are just dirty, alcohol or contact cleaner should work.
If they are corroded or with a rough surface, not much to do with it and better interchange with an Omron as mentioned earlier.
 
Thanks for all helpful suggestions, especially about cleaning the contact surfaces with care. I certainly don't want to make the problem worse.

My first challenge is opening them up, so I will dive in next weekend.
 
James said:
Thanks for all helpful suggestions, especially about cleaning the contact surfaces with care. I certainly don't want to make the problem worse.

My first challenge is opening them up, so I will dive in next weekend.
Click to expand...
Yeh, the transparent plastic casing seems to be old/yellowished so better be careful.
You may heat it up a little bit with a hair dryer before prying it, it may become a bit more flexible.
 
Gervais Cote said:
Yeh, the transparent plastic casing seems to be old/yellowished so better be careful.
You may heat it up a little bit with a hair dryer before prying it, it may become a bit more flexible.
Click to expand...
This is the reason, why I suggest cleaning electrically, no need to open the plastic, which will be brittle by now.
 
davidsrsb said:
Power relays depend on a wetting current to keep the contact faces clean. Too much "dry" switching with no current flowing and the surface gets oxidised.
Switch a power resistor to a lowish supply voltage eg 5V at about 1A can blast the oxide off. This would need a 4R7 resistor on 5V or 10R off 12V
Click to expand...
How long does this need to be activated to clean the contact? How can I be certain that a less that perfect contact won't be made worse with arcing?
 
It is the opening and closing that cleans the contact. So open and close tens of times.
Arcing is to be avoided, which is why you use a resistor load and keep the voltage down.
If the contacts are so chewed up that the relay gets worse, it is beyond repair.
 
The Revox A77 has three similar relays that need cleaning from time to time
Use a fine, wide flat tool to gently prise those retaining covers off.
There is a rocker spring on the top of them and if you remove the spring the rocker contacts can be withdrawn for better access for cleaning.
I use a fibre pen and deoxit to clean the contacts
IF you cant withdraw the rocker assay I just use card paper soaked in deoxit then flush with Isopropanol

IMG_3911 by Alan Towell, on Flickr

IMG_3871 by Alan Towell, on Flickr

IMG_3867 by Alan Towell, on Flickr

Alan
 
Johnjo said:
These are excellent for cleaning relay contacts. They are effectively very slightly abrasive paper strips lightly loaded with cleaning/lubricant. You simply slide them between a closed contact and gently work them back and forward. They are much less abrasive than diamond spatulas and don’t take the tension out of the sprung contact mounting arms which can happen if you bend them back too far or for too long to clean the contacts. They were recommended to me by a relay manufacturer (very expensive multi-pole industrial relays used in gas turbine controls).

They won’t dress or shape badly pitted contacts but they are excellent at lifting light arcing and oxidisation with minimal damage to the contact surface.

https://uk.rs-online.com/web/p/electronics-cleaners/1015564/?sra=pstk
Click to expand...

/\ This
 
A piece of thin stiff card dipped in IPA and then carefully inserted between the contacts and moved back and forth will clean the contacts nicely. You can then repeat the exercise with a new bit of card with either contact cleaning fluid or a thin smear of silicone grease. Personally don't like MS4 but found RS Components Silicone grease to be excellent for this job. Use to use by the ton on TV turret tuner discs/biscuits.

John
 
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