Need help with an HP 3312A Function Gen'

Discussion in 'General Electronics Chat' started by Gazucha, Sep 12, 2013.

  1. Gazucha

    Thread Starter New Member

    Jan 28, 2012
    Hi all,
    recently aquired an HP/Agilent 3312A which had been somewhat neglected. It had apparently sat unused for some 7 years!

    Anyways, apart from some mild corrosion around a very few solder joints and 3 missing control knobs, it was complete and in fair condition, so was cleaned - inside and out - before being switched on.

    Unfortunately the main generator output (Vp-p) and Sync output give no waveforms at all. There appears an adjustable DC voltage from the Vp-p (if I remember correctly, up to 12v) but no sine, square nor triangle waves. The output impedance test came back fine too.
    On the second channel (Modulation) we do have all wave varieties but only into low Khz.

    This leaves me thinking main channel frequency generation failure.

    So before I spend hours to get my head inside this unit, does anyone know where the frequency originates in a 3312A? Or can give a heads-up to possible fault location?

    The Service specs can be found here...

    I should add that a few of the blood-red, mica caps have become slightly blackened.

    Pictures galore can be provided if required.

    Any help would be great and well appreciated.
  2. gootee

    Senior Member

    Apr 24, 2007
    Start at page 4-1 of the manual from the link you posted. It is explained, there.

    Then look at section VII (7). See Figure 7-1. The integrator and comparator (triangle generator) are in the upper section. Then see Figure 7-2 for their actual circuits.
  3. RichardO

    Late Member

    May 4, 2013
    One other condition that can prevent the output signal from changing is the trigger/gate function. Try turning the trigger phase knob to the "free run" position.