Cannot hear dial tone on WE Model 500CD

[Rotorman]

Thanks so much, Victor & TelePlay for getting info posted so quickly.  So glad I came to this forum. 

[MaximRecoil]

Contact cleaner is seldom useful in telephony. The SWHK contacts, and the contacts on most relays and keys, are designed to be self-cleaning. They have what is know as "follow" a concept that allows contacts to wipe as the make, so that dirt does not build up on them. Without that concept, the entire System would have fallen apart quickly, if you consider that there are a gazillion contacts in a CO, and another gazillion contacts in all the phones out there.

I disagree with your first sentence. Phones that aren't used very often or have been in storage for a long time, can develop problems due to dirty/oxidized leaf switch contacts. For example, I have a 554 that made a staticky sound through the receiver when pulling down or releasing the hook. Spraying the set of leaf switches connected to the hook with contact cleaner fixed that instantly. Also, I have a 500 that usually didn't shunt the receiver when dialing. Spraying the shunt leaf switch in the dialing mechanism with contact cleaner fixed that instantly. Both of those phones are normally in storage. I take them out from time to time to clean the dust off them and test their functionality.

Also, the contacts in modular plugs and jacks can oxidize too, given that those are normally just plugged in and left plugged in for long periods of time. Unlike spade terminals clamped down tightly in screw terminals (as in the connections to the network), modular connections are not airtight. When oxygen can reach the contacts, oxidation can happen.