Ensoniq TS-10 repair

Field Notes

Keyboard Calibration Error

  • TS-10 and ASR-10 use essentially the same keybed 
  • Schematics for Upper and Lower boards from Tauntek - a godsend!
  • A healthy board initializes without error 
    • With no keys installed
    • With some keys installed

single_key_installed
 

This can be useful when troubleshooting - no need to completely install the keys just to test 

 I was also able to install a few of the keys and power up the synth, play those and ensure all is working and progress from there

  • When the "Keyboard Calibration Error" is displayed, keyboard scanning seems to operate normally - you can scope the HC238 components and U1,2,4 for scan frequencies:
    • U2 legs 18,19,20,21 show the L/C frequencies as described in the schematics above ("Lower")
    • U3 legs 2,3,4,5 are the A0..3 lines - controlling the 4 HC238 chips
  • When bared, make sure your hands are not near the keybed during initialization - even resting your finger on the board may produce a failed initialization
  • The measured frequencies on U2 legs 18-21 should be as close as possible to what's documented in the schematic - even a 2 Hz difference caused one keybed to sometimes fail initialization 
  • Note that U3 is packaged as a PLCC, the pin numbers differ from what's in the schematics 
 

 

Aftertouch problems 

I encountered a scenario where black keys responded to AT but white ones did not.
Apparently The "bushings" - little rubber pieces underneath each key, (in white on the above image) - have a "hard" and "soft" direction. Make sure to install them with the "soft" part facing up    
 

 Headphone Jack only one side

I was able to trace this to the motherboard: U63 is a programmable device which should provide 2X 29.7Mhz to the "Analog" board. this signal is used to demultiplex analog audio signal into L/R by controlling a couple of analog switches.
the architecture is:
DAC uses a TL702AC to convert the Main and Aux streams, keeping both L and R multiplexed. this is then sent to one analog switch per Main and one per Aux, demultiplexed and sent to analog output stages 
 

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