Does anyone know what the benefits / drawbacks of different relay contact compositions are, specifically gold over silver vs gold over silver palladium?
The context is a SPDT relay used for channel switching in the preamp of a Marshall head. The relay sits between between 12AX7 stages. The original part has gold over silver palladium contacts, but is impossible to find from Marshall or anywhere else (it was discontinued decades ago). What I have been able to find is a model from the same series identical in every specification except that it has gold over silver contacts.
A search online tells me that gold over silver palladium has better resistance to oxidation and sulfidation than gold over silver, but I have no idea if those are likely to be a practical issue in this application. I have no way to know if Marshall specified the contact composition for a reason or just used what was available.
It's appealing to use the one I've found since I know it will drop in to the amp mechanically and electronically without any adjustment whatsoever. If the composition difference is unlikely to make a practical difference then it saves finding a different relay which may require an adapter board or tweaks to the surrounding driver circuitry.
The context is a SPDT relay used for channel switching in the preamp of a Marshall head. The relay sits between between 12AX7 stages. The original part has gold over silver palladium contacts, but is impossible to find from Marshall or anywhere else (it was discontinued decades ago). What I have been able to find is a model from the same series identical in every specification except that it has gold over silver contacts.
A search online tells me that gold over silver palladium has better resistance to oxidation and sulfidation than gold over silver, but I have no idea if those are likely to be a practical issue in this application. I have no way to know if Marshall specified the contact composition for a reason or just used what was available.
It's appealing to use the one I've found since I know it will drop in to the amp mechanically and electronically without any adjustment whatsoever. If the composition difference is unlikely to make a practical difference then it saves finding a different relay which may require an adapter board or tweaks to the surrounding driver circuitry.
Some references in my dropbox for a short period of time: https://www.dropbox.com/scl/fo/vabr..._5QQFfAs?rlkey=sw351au633hed51ek4xsl0sbs&dl=0
Thanks Mark! Some of this may test my high school-level math and physics education but I will give it a go!
Just buy a mil grade hermetically sealed relay with the same mounting style and coil voltage / contact layout.
Or if it is simply on-off action, a solid state relay may work. YMMV...
Researching the contact details is not useful, you have a limited number of relay makers, and your choice of suppliers for a small quantity is limited.
Military grade relays are built to a higher standard, and the layouts stay the same for decades, unlike the frequent changes in consumer equipment, where a washing machine control circuit goes unobtanium within 5 years.
A useful source may be sellers selling old military surplus stock. And those may be as old as the amp, so good chance the materials used are nearly original.
Just check the frequency of switching specified, if at all, and get the highest rating available for long life, the price differences are nominal for different contact ratings in the same build style.
The reputed names in tiny signal relays are a very small group, Omron, Panasonic, O/E/N (French technology, made in India), and a few others.
Just select the unit available, it is now a limited selection, and many models are EOL, or about to go obsolete.
I had a hard time finding tiny Omron signal relays, those are like 20 x 15 mm, finally found them on RS India for about $3.50, got 20 instead of 8, they were not in stock at Mouser, element 14 and others even in the USA.
They are an essential item for my friend's offset printing machine, it has many, one gone means machine down.
So I would order a few extra, and check the landed at door cost.
No ties to any names above, as usual.
Or if it is simply on-off action, a solid state relay may work. YMMV...
Researching the contact details is not useful, you have a limited number of relay makers, and your choice of suppliers for a small quantity is limited.
Military grade relays are built to a higher standard, and the layouts stay the same for decades, unlike the frequent changes in consumer equipment, where a washing machine control circuit goes unobtanium within 5 years.
A useful source may be sellers selling old military surplus stock. And those may be as old as the amp, so good chance the materials used are nearly original.
Just check the frequency of switching specified, if at all, and get the highest rating available for long life, the price differences are nominal for different contact ratings in the same build style.
The reputed names in tiny signal relays are a very small group, Omron, Panasonic, O/E/N (French technology, made in India), and a few others.
Just select the unit available, it is now a limited selection, and many models are EOL, or about to go obsolete.
I had a hard time finding tiny Omron signal relays, those are like 20 x 15 mm, finally found them on RS India for about $3.50, got 20 instead of 8, they were not in stock at Mouser, element 14 and others even in the USA.
They are an essential item for my friend's offset printing machine, it has many, one gone means machine down.
So I would order a few extra, and check the landed at door cost.
No ties to any names above, as usual.