I have quite a few 400 type KTUs as backup to my 1A2 system. Each KTU is bubble wrapped, and stored horizontal (as they would be installed). They are kept in an air conditioned area. I have found the same leaky green goo from a small percentage over the years, and it is easily removable with no apparent damage to the KTU. While I have other KTUs (e.g. Manual Intercom, Power Failure, Tie line, etc), the 400 D is the only one I have found the green leakage on.
Both this an one other ancient thread regarding “
green goo” leaking on
WECo 400D circuit boards questioning whether it is toxic or not.
At the time (1971-72), it was well known since it was causing major problems with 1A2 key system line cards (400D) as well as other circuit packs used in some PBXs in the Bell System.
Bell Labs performed an in depth investigation that revealed major problems with the silicon based potting compounds (“
green goo”). Hopefully I will be able to figure out how to attach a jpeg of a page from a 1972 engineering bulletin, since it will explain further regarding some of the problems associated with this material.
[img]
https://drive.google.com/file/d/1ivmMCbwL6xHN_oUWI2C5c2qeq7c04XPY/view?usp=sharing[/img]
