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Altec 1592B Mixer Amplifier Rebuild, Pt. 1: Overwiew and Initial Disassembly

It's Altec week in The Dungeon.

Or should I say, Holy Anaheim!, what's that? (Anaheim, California was where they were made).

This is an Altec 1592B Mixer Amplifier - a 5-channel preamp/mixer. Sort of a super deluxe version of the 1589B I just worked on.

Five inputs with high/low gain switches for each. Plus a master output, high and low frequency controls and a bright switch. And a big VU meter and a monitor output.

It takes up three rack spaces.

If five inputs weren't enough, Altec sold a six-input mixer, the 1599A, that could be connected to the 1592B to give more inputs. In fact, the manual for the 1592B shows how to connect 5 of them with a 1592B to give 30 inputs!

What I'm wondering is how one keeps all these model numbers straight. Funny thing is, I'm actually starting to know which is which.

Anyway, as with the 1589A, I'm going to recap and upgrade this one so I can use it for recording.

This is the rear panel. Just like the 1589B, there are XLR inputs, sockets for the input transformers, and a terminal strip for outputs.

Note the two filter cans as well. I'll be replacing these.

One of the 5 input transformers (it came with 1588Bs) is not plugged in - that's the one I dissected in the last post.

The front panel drops down for servicing. I can't tell you how much I like this feature.

It does look a little overwhelming, but there are really three main sections: first, the chassis itself, which contains the input jacks, the sockets for the input transformers, the filter caps, and the front panel and its controls.

Second is the main PC board, which Altec refers to as the Power Amplifier board. This is the circuitry to amplify the input signals, pass them to the tone controls if selected, and then send them to the output transformer.

I've also highlighted the location of the two filter cap cans. They're riveted to the chassis, so I'll be drilling the rivets out.

The third section is the Tone Control board, mounted to the front panel. It also has a 1K tone oscillator built in!  So cool.

I'm working on the Power Amplifier board first.

There are two connectors to remove. Mine were really stuck on - I just gently but firmly wiggled back and forth and they came off.

Then four screws that hold the board to its standoffs on the chassis.

Three of mine came out easily.  One was recalcitrant.

Fortunately, the screws are accessible from underneath (actually from the rear panel). I sprayed a touch of PB Blaster penetrating oil onto the screw threads, and the screw came out easily.

Put the board into the amazing Aven Adjustable Circuit Board Holder and we're ready to go to work.

In front of the board you can see its schematic and layout. I marked it up so I'd know what to replace and with what component.

There's enough clearance in the chassis that I can bend the leads on the new radial style capacitors so they'll stand up. I gently bent them with some hemostats.

Here's that same cap installed on the board. Nice and tidy.

All of the electrolytics are done. Elna Silmic IIs for signal caps and Nichicon FGs for bypass.

Next I'll change out some of the resistors. Takman REY metal film for transistor collectors and Takman REX carbon film for signal resistors.

Here are the old electrolytics I removed. The blue ones in the middle are Mallory caps; I suspect they are original. The silver one is a Mallory also. The big one (1000uf/25v) and the two small caps have no name - they're just labelled "Made in Mexico."

Altec 1592B Rebuild Project
Part 1: Overview and Initial Dissassembly (This page)
Part 2: Power Amplifier/Main Board
Part 3: Tone Control Board
Part 4: Filter Capacitor Replacement
Part 5: Reassembly

 
 
 
 

Post a Comment 2 comments:

  • Monoteur said...
    November 23, 2016 at 2:34 PM
    Hello,
    i'm planning to mod the Altec to an mic preamp, but i can't find any schematics in the web. Do you have all the schematics? Can you maybe send it to me?
  • Yr Fthfl Blggr said...
    December 19, 2016 at 2:57 PM
    Manual is here:
    http://www.greatplainsaudio.com/vintage_altec/1592B_rackmixer_ALL_Part_1.pdf

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