Bozak CMA10-2, Stereo 10 channel mixer
An early Bozak stereo mixer with discrete electronics, Sealed Allen Bradley Pots, and transformer coupled mic preamps. Restored to full operating condition.
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Bozak CMA 10-2 stereo mixer. 10 input channels, 9 have removable Bozak octal plug in transformers for the mic inputs, #10 is a direct coupled unbalanced input. There are 2 XLR outputs, both unbalanced with Pin 3 hot, a stereo TRS output, and RCA tape outputs. The input preamps are discrete cards using pairs of Motorola 6521 transistors. The output cards use RCA 40406, 07 and 08 transistors.
Additional photos of the reconstruction available upon request.
Each channel can be assigned to the left, right or both outputs, there is no balance control, phantom power or channel EQ.
A slide switch on each channel selects between a fixed EQ (lo cut filter) for either Speech or Music (flat response).
There’s an internal oscillator that feeds channel one, and can be used for setting up levels downstream. The Meters work fine, but there are no calibration controls for the meters or the output levels.
There are bass and treble controls for the Left and Right output channels.
All of the controls are Allen Bradley (AB) hot sealed pots, Type J, one of the highest quality controls available anywhere, anytime.
The condition of this mixer was pretty poor when we started work on it. Several channels were dead, the oscillator wasn’t working, there was no Right buss output, and the case was covered with old tape and label residue, grime, ink stains, scratches and missing hardware.
Summary of repairs:
- complete degreasing, cleaning and Cramolin treatment of all unsealed pots, switches, contacts and jacks
- Install new grounded power cord
- Replaced 5 primary electrolytic caps in power supplies
- Replaced coupling caps on several input preamps
- Repair output amplifier
- Replace missing CH10 attenuator switch
- Correct short to Right channel output buss on Ch10 assign switch
- Install gold plated Switchcraft A3Fs on all inputs
- Install new RCA jacks (tape outputs)
- Deoxed, polished Main output A3Ms connectors and Monitor output
- Install polyethylene pcb and transformer retainers.