[time-nuts] HP ET2702 5 MHz distribution amplifier

[Bob Voelker]

Does anyone have any information, specs, or
history of the HP ET 2702 5 MHz distribution
amplifier?

I suspect that it is a very rare unit,
based on the "ET" model number prefix.
Could it be the predecessor of the
HP 5087A distribution amplifier?

I have neither the HP 5087A nor its
manual, so here are notes on my
ET 2702 for comparison:

   -One 5 MHz input and ten 5 MHz outputs,
    all on rear panel.
    
   -Front panel has 13 labeled holes for
    inserting a screwdriver to adjust the
    gain of each of the 13 amplifier 
    modules inside.
    
   -Front panel pushbutton power switch has 
    a guard to prevent accidental shut-off.
    
   -Cabinet almost same size as HP 5087A, 
    except for being 5 inches high.
    
   -Traditional 1960's HP blue color scheme
    for cabinet.
    
   -Serial number plate on rear does not
    use the usual HP 1960's or 1970's-on  
    format.  The number suggests 1968.
    
   -Components inside are date-coded 1968.
   
   -Inside, there are 13 unmarked, seemingly
    identical, fully-shielded amplifier
    modules of roughly 4 x 2 x 2 inches in
    size.
    
   -Architecture consists of the output of
    the first amplifier driving the parallel-
    connected inputs of two following 
    amplifiers, and these amplifiers in turn 
    each drives five amplifiers, providing 
    ten outputs that go to the rear panel.
    
   -Each fully-shielded amplifier module has
    two parallel-connected SMB input jacks,
    one BNC output jack, and one gain-adjust
    potentiometer.
    
   -Each amplifier module contains two
    cascaded 2N708 NPN BJT common-emitter
    amplifiers with the collector of the
    second stage loaded with a tuned-primary
    transformer.  The transformer's secondary
    is untuned.
    
   -The PCB inside the amplifier module is
    labeled "05060-6023", suggesting that it
    might be related to the HP 5060A cesium
    standard.
    
Thanks for any info,

Bob

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