Dreaded foam.

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You've likely heard mention of   "The Dreaded Foam" from time to time.  Many people have asked - What is it?!?  Our explanation usually is pretty brief but in reality this dreaded foam is quite dreadful!

Before we elaborate on specifics let us explain the pitfalls of decaying foam.  
Over time the Petroleum based foam deteriorates and transforms into a caustic tar-sludge like substance. If you are not familiar with the word caustic its definition is "capable of burning, corroding, or destroying" in the case of foam inside an instrument it can burn, corrode or destroy wires, jacketing, plastic surfaces, sliders, switches, circuit board traces and so on. Generally this foam was used to isolate and protect electromechanical parts like pots, faders, switches etc from dust & debris- Except that nobody knew that in 30-40 years time it would become a major headache!

Hammond Organ used foam starting mid 60's straight into the 1970's as an isolator for resistance wires inside the manuals (keys). Keep in mind that each resistance wire is hair thin and each key has 9 wires. Multiply 9x61 keys and you have 549 chances for the foam chew thru a resistance wire and eliminate a tone in your Hammond. The foam removal process is tedious. With the back panel removed from the manuals you can see sludge like substances adhered onto the outer layer of resistance wires and the phenolic grid which holds the resistance wires in place. 
Take a look at the pictures below!

 

 

 

Note: black sludgey substance adhered onto the resistance wire and comb.


Tedious cleaning process!


While de-foaming its important to remove all loose bits.


Decaying foam.

The foam is back again surprise!!!  Moog used similar foam in early 80's synth's such as the Opus 3, Rogue & Liberation.
From a conceptual standpoint foam was great solution as a barrier to keep dirt, debris and what not from getting inside but little did anyone know!   Take a look at the before and after pictures below. Cleaning of this Opus 3 board required 3 hours to complete, that excludes necessary trace and fader repairs.


Opus 3 main circuit board. The foam has chewed on plated surfaces and bonded with most of the flat
surfaces in addition to making its way into the faders effecting their functionality...


More foam!

After: Foam removed!! All the faders, pots and switches required internal cleaning, flushing
and lubrication. The board itself was gone over with solvents to remove all residue. The process
required most of an afternoon to complete. You can see how this foam chews plated surfaces note the rusty
looking edges on most of the metal surfaces...