Ensoniq SD1 issue

Discussions about anything analog, digital, MIDI, synth technology, techniques, theories and more.
Rasputin
Senior Member
Senior Member
Posts: 810
Joined: Thu Jul 21, 2016 4:52 am

Re: Ensoniq SD1 issue

Post by Rasputin » Tue Mar 28, 2017 3:01 pm

madtheory wrote:It's highly unlikely, I think, that external MIDI input gets routed through the keyboard control circuitry. That's for converting mechanical movement in the Ensoniq's keyboard into control signal. MIDI already has the AT encoded.

Looking back at your original description of the issue, it looks like the actual pressure sensors are working fine, but the behaviour with the pedal would suggest some kind of bad ground or inconsistent loading or interaction of CV signals on the analogue side, or maybe at whatever point those signals are mixed, or multi-plexed (don't know if they are or not). So I'd look at everything before the ADC (I assume there is one taking in keyboard and pedal voltages) input.
Correct. MIDI gets decoded by the UART and then sent directly to the CPU. I believe the Ion doesn't have aftertouch at all, so I agree with the conclusion that it is a problem local to the SD-1's KPC board.

As far as things likely to blow, Q1 and Q2 on the KPC PCB are the most vulnerable items dealing directly with the footswitches prior to them being read by the main keyboard handling processor [Motorola 68HC11A1P] which--as could be guessed--also handles the final steps of keyboard processing before passing the CPU tidy packages of footswitch, keypad, and keyboard data.

KPC BOARD OPERATION

Motorola 68HC11A1P is the main brain in the keyboard processing board:

Port A selects which group of music keys are currently to be scanned and also reads in the state of the footswitches
Port B is addressing (exclusively)
Port C is address/data lines which gets data to/from the EPROM and KPC chip
Port D is serial transfer to/from the mainboard and the display/keypad PCBs

74LS373 is a latching IC that demultiplexes Port C of 68HC11 into separate data and address streams.

The EPROM (27C256) contains the instructions for the operation of 68HC11.

The KPC CHIP [U3] handles the reading of the actual music keyboard:

F0~F3 are output lines coming from the keyboard, to be decoded by the KPC chip and the result is forwarded to the 68HC11; the result of F0~F3 is dependant upon which keys are currently being driven by 68HC11 Port A (CS0~CS3).

68HC11 processes both the display/keypad button and music key data and then sends it to the mainboard as serial data.

As far as the actual inductance functionality goes, this thread explains the theory of operation:
http://electronics.stackexchange.com/qu ... d-function

alfadawg01
Junior Member
Junior Member
Posts: 107
Joined: Thu Jun 30, 2005 7:14 pm
Gear: Ensoniq SD1, Alesis Ion, iPad2 (running Animoog, Galileo Organ, iM1, iWavestation, Mellotronics M3000HD, & ThumbJam), Roland VR-09b.
Band: The Journey Worship Band
Location: St. Louis, Missouri, USA
Contact:

Re: Ensoniq SD1 issue

Post by alfadawg01 » Tue Mar 28, 2017 8:50 pm

Rasputin wrote:Just as a heads-up, unless you sourced the 68HC11A1P directly from another Ensoniq (such as a chip pull from Syntaur, etc.) then you'll likely have a completely non-working keyboard when you swap out the chip. The 68HC11 has 512 bytes of on-chip EEPROM which can (and, in this case, needs to) be programmed with custom code.
The 68HC11A1P I ordered arrived yesterday and was installed. No change in the SD1's behavior and it works fine otherwise. The chip was not sourced from another Ensoniq.
Rasputin wrote:Out of curiosity, does the behavior change if you go into MASTER and change TOUCH to HARD4?
The behavior is consistent with each touch setting.

alfadawg01
Junior Member
Junior Member
Posts: 107
Joined: Thu Jun 30, 2005 7:14 pm
Gear: Ensoniq SD1, Alesis Ion, iPad2 (running Animoog, Galileo Organ, iM1, iWavestation, Mellotronics M3000HD, & ThumbJam), Roland VR-09b.
Band: The Journey Worship Band
Location: St. Louis, Missouri, USA
Contact:

Re: Ensoniq SD1 issue

Post by alfadawg01 » Tue Mar 28, 2017 8:52 pm

madtheory wrote:So in addition to Rasputin's suggested test- are you 100% certain that AT is working on your Ion?.
The Ion's keyboard does not transmit AT.

Post Reply