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I can tell you that 327A is the nomenclature for the actual reed relay component and the 72K is the date/period of manufacture (1972 was the year).
Upon reviewing other cards of similar design, I found some of a later date of manufacture where this reed relay was marked 327L, so I'd guess that the Delta was meant to signify that the relay's part number was actually 327D.
There are no potted components on these cards except for whatever "mystery" component may reside within this reed relay. Since they were marked "Contents under pressure-do not open", most people took heed to this warning and never bothered to experiment.
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From the description, it really seems like the "green goo" might indeed be a potting compound that liquifies, as WE apparently went to some efforts in later revisions to remove the compound. According to the docs the contacts are dry and sealed. Since it's a reed relay, typically the contacts are sealed in glass.
In case the above link describing the relay goes stale, I'm retyping what it states (not responsible for errors):
Code
.............................................................................................
: AUGUST 31, 1979 | NO. 327 TYPE RELAYS | :
: | (Card No. 2) | :
: ___________________|__________________________________________________|__________________ :
: :
: No. 327A, F & G: Non-adjustable relays consisting of No. 237E dry sealed contacts :
: housed within a double winding coil contained in a metal case. :
: Arranged for mounting on a printed wiring board. :
: The two reeds in the sealed contact will make contact (operate) and release :
: when either winding of the coil is energized, at the values specified. :
: :
: No. 327B, C, D, E, M & N: Similar to No. 327A except each is equipped with one winding :
: and four terminals. :
: :
: No. 327H: Same as No. 327A except potting compound is eliminated. :
: Not approved for general use. Approval must be obtained from the Apparatus :
: Applications group. :
: :
: No. 327J: Same as No. 327C except potting compound eliminated. :
: Not approved for general use. Approval must be obtained from the Apparatus :
: Applications group. :
: :
: No. 327K: Similar to No. 327G except has a trifilar winding with the third winding :
: shorted internally for low AC impedance. :
: Contain No. 237H dry sealed contacts. :
: :
: No. 327L: Similar to No. 327F except contain No. 237H dry sealed contacts. :
: :
: No. 327P & R: Similar to No. 327B except have minimum board to relay clearance :
: of 0.55 inch, a height above board of 0.68 inch, and an overall height :
: of 0.82 inch; instead of 0.02 inch, 0.064 inch and 0.78 inch, respectively. :
: :
: Property of the Western Electric Company, Incorporated Printed in U.S.A :
: :
:............................................................................................
Last edited by Greg Ercolano; 12/13/2204:38 PM. Reason: Changed link to be "clickable"
Followup: for the laffs (and for the Gipper), I decided to desolder a 327A / _72K from one of my 400D line cards.
This seemed to have the exact same type (327A) and same year (First quarter 1972, if I remember the WE dashed date codes correctly) relay as has been reported here and elsewhere. My 400D did not have the leaking problem.
But once I started de-soldering it (would not recommend, lol) apparently the heat caused the green goo to start squirting out of all 4 corners of the relay, as this sequence of photos shows:
Yep, there's yer problem. I love the sticky gooey detail in that second photo. As I wrote on Phil's 1A2 facebook group, it's like dissecting a frog with taffy for blood.
One thing I haven't figured out is why my goo is a light green. Everything I've seen so far, the goo is typically a dark green, similar to the dark green solder mask on the 400D card, which by the way also turns into sticky goo when heated.
Anyway, thought you all would be interested -- I did it so you don't have to. Would not recommend trying to repair these particular relays by de-soldering, unless you're prepared for a sticky, stinky gooey mess. Yuck!
Looks like the folks at the Connections Museum up in Seattle have also run into the green goo problem with most of their No. 5 crossbar switch's 316-type removable potted relays. Some interesting details in the video about those, the trouble the goo causes for unprotected relays beneath them, and their goo cleanup effort:
Connections Museum: Emergency Repair in the No. 5 Crossbar
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.
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]
I wonder if you get some 4" diameter heat shrink tubing. And make it short enough not to cover the handle and pins of the KTU. If that would help to prevent the green goo leaking onto any equipment. .
![[Linked Image from seriss.com]](https://www.seriss.com/people/erco/tmp/400D-desolder--327A--72K.jpg)
![[Linked Image from seriss.com]](https://www.seriss.com/people/erco/tmp/400D-linecard-green-goo--desoldered-L-relay--type--327A--72K.jpg)