LS-685/U Crystal Loudspeaker
NSN: 5965-01-295-1125© Brooke Clarke 2013
This military speaker is designed to be light weight. It has a plastic case instead of the normal cast metal case and a crystal speaker element instead of a classical coil and magnet type speaker (typically with an audio transformer).
Back of speaker
Front of speaker
Close up of front of speaker
Connector Markings
Opened Connector
A normal U-229 type plug has 3 pins in the metal
housing w/ 120 deg spacing, but the OCS66 shown
above has 4. The extra pin is shown at the top center in the photo.
The LS-454/U speaker that was used with the VRC-12 series VHF low band radios used pins A (ground) and E (non standard) as does this speaker. The common pins for an earphone or low power speaker are A and B (see U229 Pin Out web page).
The connector that looks similar to the common U-229 is in fact a PCI OCS66 that seems to be designed to NOT mate with common NATO audio connectors.
The speaker driver seems to be made up of a sandwich of three layers: metallic cloth for one terminal, the piezo material in the center and another layer of metallic cloth.
The speaker cone is a very stiff and light weight material, maybe some type of fabric that's been stiffened, like fiberglass or phenolic.
Maybe it's the Model # MP-1103 (pdf version) speaker element?
Questions
I got two of these and they are both dead.They are alive, but need a new connector in order to test.
If you have a working speaker:
TM-11-5820-890-10-8 SINCGARS Ground Combat Net Radio ICOM Manual
1) what DC resistance do you see across the terminals?
ans: The Fluke 87 DMM shows rising resistance, i.e. a capacitor
2) what happens if you scrape a wire connecting a 1.5 Volt Alkaline cell to the speaker terminals?
ans: At first contact there is a click, but further contacts produce no sound.
Reversing the polarity causes one click, but no more with the same polarity.
3) What equipment does the PCI OCS66 connector mate with?
ans: C11561 SINCGARS Full Size Remote
says:
This is the only loudspeaker that can be used with the RCU speaker connector.
Military Audio Accessories
Audio Connectors
U-229 Pin Out
U-229 Audio Accessories
VIC-1 Vehicle Inter Communication
VRC-12 series radios
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page created June 19, 2013
