Some interesting vintage (or antique?) Altec modules

[rkc7]

I got these off of Ebay because they looked interesting and were cheap... so anyone want to have a go at what these were for or can be used for?

Altec 453B Amplifier (x2)
Altec 455 BX Amplifier
Altec 533A Power Supply (x2)

http://photobucket.com/albums/a272/s...ier%20modules/

They're marked as power supply and amplifier, which they go together, but I haven't dared plugging the thing in. For one, both power cords are looking a little frayed and one of the supplies is missing the ground prong. Second, these things look OLD, who knows if any of the caps dried up or what not.

Anyway, check out the pics.... they look like some really old solid-state amplifiers and the only transistors I can see are GE 2N191G and GE 2N188A, which I looked up and are listed as low power bipolar junction transistors, both PNP and the 188 good for 180mW and the 191 good for 75mW. Could these just be old radio amps?

[Hornlover]

They look like EQ modules. Altec, and others back then, used to make custom equalizers. They plugged into a rack that would hold up to eight or so modules, each tuned to a certain frequency. They were set and forget, used to voice a loudspeaker system for a given venue. I remember seeing a picture of an assembly once some time ago. This is my best guess.

[LAJ]

The Altec 453B amplifier is a piece of telephone equipment. It is a repeater amplifier capable of about 36 dB of gain. It dates from 1972. It is a one way type repeater amplifier. It uses 2 PNP transistors and operates off 24V DC. It takes an 11 pin octal style connector. The response is about 3500 Hz (VF=voice frequencies) but this can been changed with component changes. It has balanced inputs and outputs.
Repeater amplifiers are very common in telephone systems. And it depends on if its a 4W system (office to office trunks) or 2W systems (customer lines). The telephone company learned early on how far you could go before you need to amplify it. I have heard that some repeater amplifiers were located in manholes but I don't know how they kept the water out.
I have a schematic if you need it.

[LAJ]

Not many people know this but Bell was into all kinds of services.
There was an L5 system which was coaxial and used RF amplifiers much like todays cable TV systems. It carried voice channels and RF video. I believe it was last used to provide video services to schools.
And then there was the A3a system. It was a baseband video service to TV stations. It used 2 wire shielded coax (124 ohm twinax). Before the TV networks went to satellite, network video arrived to the TV station via microwave or twinax from the local Bell office. In many cases the TV stations were only a few miles from the Bell office. So it was cheaper to twinax it to the station rather than microwave it. The video feed had to be equalized at the station to make it flat.
Of course, all this has been replaced with fiber optics. And they probably do more data than voice these days.

[awnobles]

I have some wired as mic preamps. I recapped them and they sound good but no bass. I would welcome any input on modding to lower high-pass frequency. The germanium transistors and the transformers sound good. I can't figure out the circuit so I stopped there. The schematic would really help. awnobles@ev1.net

[musika]

Thanks to LAJ for the good info on the 453b line repeater amp. I've purchased a few of these and would like to modify them for either line amps to add to the monitor or line outputs to my A&H MOD2 console. Does anyone know the mods needed? I've followed the circuit using the spec sheets, but I'm puzzled on how to mod for full frequency. The specs say 200-6K for original frequency response. Any ideas?

[LAJ]

[IMG]e:\453_back[/IMG]