sundance-communications.com Forums More-Phone & VoIP Systems 1A2 and Comkey Telephones & Systems 760A Loudspeaker

Hi,

What was the 760A loudspeaker used for?

I just scored one for 9 bucks on e-pay that some nincompoop had screwed a four prong plug onto its side. I am going to remove the plug and attempt to fill the holes with chemically melted ground up plastic from a the shattered shell of a green 500. I will first try acetone, and if that does not work, I will try using hot toluene. Failing that, I might (in a high flow fume hood in a chemistry research lab) try using ether in a steam tank... that should melt any plastic. I will see if this works, and if it is at all successful, I will post pics about it.

Joe

PS I just got a line on a Klienschmidt reperf! In negotiations for it right now. More to come.

It is just a basic amplified speaker that will deliver whatever you send to it via the tip/ring pair to allow others in the room to hear both sides of the conversation. They can't talk back, though. They offered many purposes, but the most common was to just connect the tip/ring to the handset receiver terminals inside of a phone.

The black/yellow pair requires 13.6VAC to power the amplifier.

Well, my 760A speaker has arrived. Some of you might have seen it on e-pay. It was (is) filthy. The good news is that the butchery done to it was a lot less obnoxious than I thought that it would be. Before I go on, here is the silly thing before I did anything to it.









It was not obvious on the e-pay description that there was a stub of the original wire left. I had wrongly assumed that there had been a hole drilled underneath the four prong plug that had been screwed onto the side of the unit to pass the connecting wires through. Thankfully I was wrong, and there were only two very small little holes where the sheet metal screws had been driven through the plastic. Unfortunately, the force on the plastic from said sheet metal screws has deformed the plastic somewhat.

Any way, here is an image of the unit after I removed the plug.





Notice the discoloration of the plastic shell. I am guessing that this is due to very long term exposure to either sunlight or flourescent light as well as environmental grundge (in this case, I believe it was a mix of smoke and auto shop grease.

After this, I took the shell off of the unit. It seems that this unit was either orignially not an amplified unit, or that at some time in its life, someone removed the amplifier. There are two extra tiny threaded screw holes in the base of the unit where a printed circuit card could have been mounted. However, the green wire stub that is attached to the speaker only has two wires in it... red and green. This makes me think that this was originally built or installed as a passive speaker with the amplification done in another piece of equipment.

Here are a couple of shots of the inside of the unit.





Since the screw holes are so small, rather than making a chemically soften mush of green plastic to attempt to fill the holes, I took tiny shards of green plastic from the shattered shell of an old 500 set and carefully jammed into the screw holes. I stuffed as much into the holes as I could using a pair of tweezers. Then I liberally applied drops of cyanoacrylic glue to the holes and shards in an attempt to weld the shards to the plastic shell. This technique worked in the past for me when I repaired a cracked keyset shell. I am letting the speaker shell sit over night to let the glue and plastic harden, then I will if necessary, take some green plastic dust, mix with more cyanoacrylic and cover any little voids that might be left.

Then I will start the restoration of the shell with a vigourous cleaning via the dishwasher, then the usual sanding/polishing process. (the unit is deeply scratched.)

I will have more photos tomorrow evening. In the mean time, does anyone know where I might find a green two wire cable for this thing?

Also, can anyone tell me if the aluminum grile is supposed to be a matt finish or is it supposed to be shiny?

Thanks again!

Joe

Joe, this may actually be a talkback speaker for an intercom. Measure the DC resistance of the speaker coil. 4-16 ohms probably no. 40-50 ohms probably yes.

It is the speaker part of a 3A or 3B speakerphone set. It is not a Spokesman® or the ITT clone, the Orator®.

The Spokesman (model 107A or B) has an amplifier inside and a 4- or 6-conductor cord. It has a volume control on the front faceplate.

ITT also made a two-way talk-back system that used a similar-looking item, the Call Announcer®. It used the same form factor but had an additional switch on the roof, and an LED busy lamp.

Call Announcer

It homed in on a special dial-selective intercom unit in the 76A KSU.

The faceplate is matte finish. A CORD (not cable) in -51 can be located easily. You can use one that has more than 2 conductors, of course. Now you need to find the 666 transmitter and the 55B control unit. Good Luck!

Arthur, you didn't waste that hold time staring off into space. You cheated and read the manuals!

@ Lightninghorse,

I did measure the resistance across the little speaker and it was right around 20 Ohms. I could hear the speaker crackle a little bit when I touched the probes to the speaker terminals.

As far as the shell, surgery went well last night. Here is a photo of the unit the next day after stuffing the holes and welding with cyanoacrylic glue.



After hardening over night, this evening, I started to smooth out the holes. Don't laugh, but I used a diamond nail file. Yes, one of those cheap give-a-ways that are given as part of 'gift packages' to women when they attend conferences.



No, I am not a woman who goes to conferences, but my wife is, and she has dozens of those things. I snagged a couple, and put in my 'phone shell restoration box'. They are really perfect for this use, as the carrier metal is aluminium, and thus are quite flexible. Swiss needle files and diamond files are not nearly so flexible, so a lot of damage can be done to the surrounding plastic.

Here is a shot of the unit after I smoothed down the filled holes.



The plastic was not quite fully hardened yet, so I took the shell and placed it in a box along with a small saucer of water and placed that on top of my TTY powersupply that I turned on. (Cyanoacrylic has to have humidity to activate and cure. The TTY powersupply gets nice and (as I call it) "kitty sleeping" warm. (The resident felines love to nap on top of it when it is turned on.)

Tomorrow, if the plastic is fully hardened, it will be baptized by dishwasher, and I will then start the polishing process. (I do use the dishwasher quite a lot in my phone endeavors, so I am thinking about installing one in my future 'phone barn' this summer.

More to come!

Joe

Joe-

The 760 is the speaker part of the WECO 3 series speakerphone. There's nothing else that went in that box, just the speaker. I don't know what you'd use it for without the rest of the unit.

Sam

Hi Sam,

I was really just testing some ideas that I had on repairing plastic shells. I picked it up for a sawbuck thinking that if I screw it up, it would be no great loss.

As Arthur noted, I am looking around for the rest of the set, but I suspect that once this little project is finished, that the unit will sit on a display shelf with other green phones. The WECO series three components are hard to come by.

One last question (well two actually)...

Was there originally a cork bottom on the unit, and if so, would it be considered cheating to cut out a new bottom from some cork gasket material? Second, Arthur referred to "...a cord in -51..." Does the -51 denote the color?

Thanks as always,

Joe

Update on the 760A shell...

I have finally completed the polishing of this thing. I wound up spending more time on it than any nasty old 500 shell that I have cleaned up. I have never seen a piece of plastic so discolored so deeply, and so beat up as well.

Took over eight hours of careful hand sanding (in order not to round the edges or destroy the 'Western Electric' logo.

But, after careful sanding and hand polishing, it is nice and shiny. The two holes that had been where the socket had been 'attached' are smooth and glossy as well, but there is just a bit of color difference between the shell and the patches. Its not perfect, (nor am I :rolleyes: ), but I am quite happy with the outcome. Tomorrow after work, I will clean the metal base, reattach the speaker to said base and re-assemble the unit (sans cord until I can find one).

I will post photos either tomorrow or monday.

Joe