No time to read your long composition. Your problem can be fixed as below stated.
It is normal for the relay 4 contact points to have oxides after 5-6 use.
Steps:
No need to replace it.
Just open the circled 2 latches
You will find 4 contacts points
There are some oxides on them.
Use a sand paper to remove the oxide and test the
conductivity of 4 points by a digital meter (zero ohm)
when press the sliver plane.
cover the relay again
see pm to see inside structure of the relay.
The long essay and photos was written and taken by me.
There are some oxides on them.
Use a sand paper to remove the oxide and test the
conductivity of 4 points by a digital meter (zero ohm)
Speaker relay contacts should never look blackened from electrical damage - the power levels simply aren't there (unless it's a big PA amp and stack), and they should be closing with zero voltage / current flowing (or you'd get a very loud pop). That's the problem, no wetting current when closing.
The most likely reason for blackening is oxidation of pure silver or silver alloy contacts. This is much more likely if there is any Sulphur content in the air, but will eventually happen, regardless, unless the atmospheric humidity is zero.
As mentioned, using sandpaper on relay contacts is terrible advice, which hasn't be relevant for decades! It has no place other than maybe old car ignition solid tungsten 'points'. Certainly nowhere that plated or flashed relays are used. Even on solid contact material, that sort of contact abrasion greatly reduces the area of the closing contacts, seriously reducing their current capacity and encouraging welding.
As floobydust said, you should never use anything more abrasive than ordinary paper, preferably soaked in IPA or contact cleaner.
What makes you think it is the rely? Make sure there is no dry solder joint on any of the pins first. If that does not help, interchange with the relay from the "good" channel. If the fault shifts with the so called "bad" relay, you can say it is bad. If not, you will have to check other possibilities.
As mentioned, using sandpaper on relay contacts is terrible advice, which hasn't be relevant for decades! It has no place other than maybe old car ignition solid tungsten 'points'. Certainly nowhere that plated or flashed relays are used. Even on solid contact material, that sort of contact abrasion greatly reduces the area of the closing contacts, seriously reducing their current capacity and encouraging welding.
As floobydust said, you should never use anything more abrasive than ordinary paper, preferably soaked in IPA or contact cleaner.
Speaker relay contacts should never look blackened from electrical damage - the power levels simply aren't there (unless it's a big PA amp and stack), and they should be closing with zero voltage / current flowing (or you'd get a very loud pop). That's the problem, no wetting current when closing.
And the result is unreliable trash.QuoteThere are some oxides on them.More likely that contacts are damaged by arcing and you remove contact material to make it less bad.
Speaker relay contacts should never look blackened from electrical damage - the power levels simply aren't there (unless it's a big PA amp and stack), and they should be closing with zero voltage / current flowing (or you'd get a very loud pop). That's the problem, no wetting current when closing.You will not get a pop, since there is only AC voltage when relay activates. For pop to happen you need DC.
And the result is unreliable trash.QuoteThere are some oxides on them.More likely that contacts are damaged by arcing and you remove contact material to make it less bad.
Here's another thought: the original relay contacts are gold plated. Gold does not tarnish, correct? So if this is occurring wouldn't that mean the gold plating is wore off and any repair to the relay would be short-lived?
And the result is unreliable trash.QuoteThere are some oxides on them.More likely that contacts are damaged by arcing and you remove contact material to make it less bad.
Here's another thought: the original relay contacts are gold plated. Gold does not tarnish, correct? So if this is occurring wouldn't that mean the gold plating is wore off and any repair to the relay would be short-lived?
Here's another thought: the original relay contacts are gold plated. Gold does not tarnish, correct? So if this is occurring wouldn't that mean the gold plating is wore off and any repair to the relay would be short-lived?
No time to see other. Only answer you!!
Gold plating??? Are you insane??!! only 12HKD. (see photo)
Why black in color?
See chemical reactions (photo)
Is cleaning these contacts a long term solution?
Of course , Not. Even you buy a new one, same
consquence happens after 5-6 year. Why due to N2
and spark. You can avoid it by making relay fully filled with
inert as, Neon only.
Or is it likely to need it again in a year? For the price I don't mind replacing because getting the PCB out is a bit of a job.
After 5-6 year, same consequence occurs due to
chemical reactions (see photo). Just try it by removing
the Cu(II)O from 4 contacts by a sand paper. Your amp
will work well within 5 years.
Just replaced on of these last weekend. I mostly see them fail on the rear channels. If you crank them up they will work again, but they will soon fail again. Sometimes bad relays even make the amp sound distorted. Relays do seem to fail al lot after 10-20 years, especially when you don't drive it that hard. Even on expensive stereo amps, I replaced a lot of them. I try to use good brand relays, especially with gold plated contacts. Most of the time they aren't that much more expensive. If you want to know if it's the relay, one way is to shutdown and startup the amp (or disable and enable the speakers, or mute them if your amp switches the relays on these settings) , and listen if the sound comes back when the relays click on again. If the sound does come back, even for a very short while the relay is probable shot.
On the last repair I tried sending some current trough them, about 1-2amps DC. I wanted to try this because the amp is old and cheap and wasn't worth trowing any money at. After this "repair" the relays measured perfect, but 3 months later the same relay failed again. Luckily I still had some of the same relays left from another amp. Just replace it, only "fix" it with sandpaper if you can't wait for new ones to arrive.
Or is it likely to need it again in a year? For the price I don't mind replacing because getting the PCB out is a bit of a job.
After 5-6 year, same consequence occurs due to
chemical reactions (see photo). Just try it by removing
the Cu(II)O from 4 contacts by a sand paper. Your amp
will work well within 5 years.
I wonder if a sealed silver alloy contact relay (like the TE part I quote above) would be ok. Maybe if I turn up the volume occasionally and make that relay cycle to burn off whatever forms on there!
EDIT: just looked through Digikey and while I'd want a "signal relay", they are rated for less than the 3A the original is. So that leaves "power relays" and none have gold clad contacts.
A 2A signal relay with the correct basic parameters has the wrong footprint. Might have to do the silver contact route.
Just for reference, no relays use bare copper contacts these days. Attacking the contacts with sandpaper is just that!
Silver contacts can be very good (lowest resistance), but do need a wiping action to keep them clean at low currents. Some relays achieve a degree of flex and wiping action. Sealed silver contact relays are better but I wouldn't guarantee that they will be reliable for signal switching (unless they are spec'd to do it).
Having been through a fair deal of audio amp repairs that at least partly involved old output relays, I'd agree to say that defective ones are almost the non-sealed silver contact ones.
Cleaning them with contact cleaner impregnated paper will usually restore them for years.
If you want longer life than the original go for gold or sealed.