[time-nuts] HP ET2702 5 MHz distribution amplifier

Daun Yeagley daun at yeagley.net
Thu Jun 30 21:56:31 EDT 2005

Hi Bob

The "ET" designation was generally used for production test, special demo boxes,
or other similar uses.  My guess is that it was an "in house" unit, and using
what was called the "next bench syndrome" may have indeed been the inspiration
for the regular production amps.


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
Behalf Of Bob Voelker
Sent: Thursday, June 30, 2005 4:15 PM
To: time-nuts at febo.com
Cc: pickypicky101 at yahoo.com
Subject: [time-nuts] HP ET2702 5 MHz distribution amplifier

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

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

   -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

   -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

Thanks for any info,


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