Reply To: Hammond Auto-vari 64 confirmed

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#8319
Anonymous
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Caution!
The power wire in the back goes directly to exposed solder joints besides the transformer, BEFORE they go into the transformer. This means that 220v is completely exposed – be careful.
I glued a piece of plastic on top of theese joints.

The service manual is extremely well written and explains allmost all circuits in detail, and combined with the fact that all connections in the machine are marked with their functions in plain english, makes the machine very easy to work with.

Installation of the Unipulse:

Very straightforward – simply cut the wires in the voiceboard connector and solder on the unipulse triggers and power. Then reinsert the connector. I attached the unipulse board to a piece of wood glued and screwed to the chassis.

Trig outputs 1-9 triggers the sounds, except brush and sandblock.

On the front of the Autovari I have installed 10 additional outputs from the Unipulse, so these can be used to trigger / synch other machines. Please note that the back panel is too thick to attach minijack outputs, The front panel is thin metal, and there is a lot of space for outputs and additional potmeters here.
Midi input installed on the back besides audio outputs.

Small corrections to the Tubbutech voice board trigger points:

Bassdrum trigger: differs from the drawing, has to be Bassdrum besides it (has a wire)
Brush has no wire in the connector, it will probably trigger if the trace is followed underneath the voice board, but I did not implement it. Strangely the Brush plays in the internal rhytems, although no visible wire is connected to it via the voiceboard main connector.
Modifications:

Low frequency output:

Seperate output for the low frequency content.
Main output contains both hugh and low content – the balance pot located on the back is moved to the front – from here the balance can be set to only high frequency content.
This way there are a seperate output for low and high content.

Pitch mods:

Easy and a must do!
I found the resistors by poking with alligator clips – the online scanned service manual is so low resolution, that the resistor numbers can not be read.

1: Bassdrum: Replace R4 with a 50k log pot
2: Snare drum low frequency: Replace R65 and R55 with a stereo 50k log pot
3: Conga: Replace R14 with a 50k log pot
4: Bongo. Replace R23 with a 50k log pot
5: Claves: R33 + R32 50k log Stereo pot (to obtain a wider pitch range)
6: Rimshot: Replace R40 with a 50k log pot
Cowbell: The cowbell consists of two seperate sounds:
7: Cowbell 1: Replace R50 with a 50k log pot.
8: Cowbell 2: Replace R58 with a 50k log pot.

Not implemented:

Sandblock CV trigger.
Brush trigger.
Decay mods.

Sync clock:

Not tested.