Tog Sw. - "Alarms - "Alert On" & "Attack On"
Knob - "Mic 1/Radio"
Knob - Mic 2/Tape/Phone"
Tog sw - Power On/Off"
Top: as is
U229 "Mic 2/Tape"
2 Terminals "Field Phone"
"Hi & Gnd""
4 Term "1, 2, 3, 4"
This is a Public Adress set that is designed to be carried on a solider's back and then used on the ground. It has a build in back pack frame and support legs. Made by Fourdee Inc. for the Marine corps. The major components are:
- AM-6482/UIA-10(V) Amplifier, Audio Frequency
- LS-608/UIQ-10(V) Loudspeaker Permanent Magnet
This is a 19" long horn type speaker that has been triple folded so it's physical length is about 9".
- MT-4537/UIQ-10(V) Mounting Plate Assembly - holds sp[raker onto pack frame
- ???? Pack Frame & Stand
- CY-??? battery Box
- ???? Control Unit
LS-608 Speaker Driver BlownThe LS-608 speaker tested DC open. It should read a reasonably low DC resistance if the voice coil is OK. Upon opening up the driver there is a spot on the voice coil that's black and in the center you can see a wire has melted. See photo above.
If you are going to attempt a repair the first thing to do is use solder wick to remove all the solder around the two 1/4" spade connectors so that after the 4 bolts are removed from the cover plate it can be lifted up free of the two internal wires.
If you take apart the LS-608 DO NOT loosen or do anything with the bolt that's in the center of the back. The purpose of that bolt is to allow the magnet to be removed once the bolt is removed by inserting a screwdriver or other tool through the hole to knock loose the magnet. Once the magnet is dislodged from the glue holding it to the driver housing it's impossible to get it centered in the housing without special tooling. Centering is needed to make the gap for the voice coil to move.
After the 4 bolts are removed use a screw driver to slightly seperate the cover plate from the housing. There is a rubber gasket at the joint and you should force it to be on one side or the other consistantly all the way around. Also there is a rubber type sealant between the cover and the housing that will need to be cut with a knife in order to get the cover seperated from the housing.
These are not really repairable, although you might be able to repair a blown coil.
I now think the failure was that the magnet came loose from it's glue killing the voice Coil and trapping it.
I'm looking for a replacement driver. The mthreads going to the horn have an O.D. of 1.36" and they have a pitch of 18 TPI.
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