The Pari XT0 and Attack Organs

Photos and text by .

The following is a slightly edited version of a post to the Hammond Forum on July 2, 2005 :

Pictures of an Attack

The Pari Attack model was a really refined model compared to the older XT0. The layout of the electronics is really nice, and there was a very nice general layout of the whole unit which facilitates service. Due to the modular design, I would guess that the manufacturing process was not necessarily done at just one location, rather the different parts could be made elsewhere and put together in an assembly location.

  • The tonewheel-drum The “tone-wheel-drum”. The pins — up to eight for each drum — are the pickups, the coils are underneath close to the tone-wheels. The magnet is positioned on the side of the retainer for the pickups — it is the dark part visible in the photo — a steel plate is glued to the opposite side of the magnet, apparently to give a more uniform field. The white connector goes to the filter-board, which is mounted separately.
  • The generator drive pulley The pulley for the drive belt (a long O-ring.) The generator is driven from a Papst-motor.
  • The scanner drive pulley Pulley for the scanner. The scanner pulley is hidden behind the aluminum cover. The scanner detects the outputs from the phase-shift line (located elsewhere in the enclosure.) Note the use of a printed circuit board (PCB) (at far end of the scanner in the photo, with cut-off wiring.) The shaft of the scanner picked up the signal, and a carbon-ring surrounding the shaft conducted the scanned signal back into the scanner-amplification circuit, which is a bit different than the “normal” amplification circuit.
  • Broken generator drive gear The misery of the PARI. The rest of the generator is silent.
  • The whole generator, bottom view The whole generator, bottom view.
  • Drawbars The draw-bar section.
  • Pedal control tablets The pedal control tablets.
  • Percussion control tablets The percussion control tablets. Note the choice of three harmonics for percussion.
  • Vibrato control tablets The vibrato control tablets.
  • Volume & Brilliance tablets The volume and brilliance control tabs.
  • Drawbar section The draw-bar section. The draw-bars operate as voltage-dividers, built up with fixed resistors in steps corresponding to the figures on the draw-bars (While Hammond used a more expensive solution (resulting in lower noise) with tapped transformers from the M series and up, the cheaper Hammonds, L100 and P100, used the resistive divider solution, like the Pari.)
  • An overview of the electronics An overview of the whole electronics.