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Bank and Wave tables can be selected either by a pulse on the appropriate input, or by pushing one of the front panel switches. The currently selected Bank and Wave are displayed by two single digit led displays. The displays used are a HP type, 5082 7340, which accept binary as inputs and include all driving circuitry onboard. A local distributor dumped the last of his stock of these devices some time in the early eighties, so I imagine they might be hard to buy now. The examples I have were picked up second hand, here and there over the last decade. Some I used while similar, were not identical, bearing the code 1990 0330.
Also of interest are the way the switches have been done. They look like membrane switches in that there is no visible cutout on the front panel for them, rather just an area marked on the artwork. The "tactile" switches themselves were salvaged from a VCR, and have been mounted on a PCB in such a way that they protrude through the
This was never intended to be any more than a project for my own synthesizer. I didn't even advertise the spare boards for sale, but due to popular demand, I sold the spares from the first batch, then had more runs made each with some changes. There are now three versions of this board in circulation.
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=== Notes ===
* In line with the four lowest address lines of the ROM on Version 1 and CGS02 boards, there is provision to place a dip switch. Four tracks will need to be cut, and pull-up resistors (4k7) soldered to the address lines of the ROM. The theory is that disconnecting these address lines, and thus reducing the resolution, creates a somewhat more "grungy" sound. I have never tried it. It was placed there after reading [[Kevin Lightner]] did the same thing. Some builders have done so and liked it, complaining when it was removed from the version 2 boards.
* One 100n decoupling capacitor is mounted directly under the ROM. It can either be placed under the socket, if a socket that leaves enough space is used, or soldered onto the back of the PCB. I used a tubular capacitor salvaged off some old computer equipment.
* Unlike most of my other modules, this one does not have the ferrite beads. If you wish to use them, you will need to mount them off-board.
* Three voltages are needed for this module: +15V, -15V and 5V. The +5V will have a significant load on it, up to 500ma* depending on the ROM used, though most likely in the 150 to 200ma range. It is probably a good idea to use a separate 5V supply, rather than hanging a regulator off the 15V rail. Both methods will work, but running the 5V rail off the 15V rail will needlessly load your 15V rail, messing it up for other modules. *Some very old ROMs were real current guzzlers.
== Parts list ==
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