[sdiy] Ensoniq ESQ-1 Serving Questions

[Nate Reeves]

"The keyboard is scanned by U1, which is a mask-programmed 6502-variant.
They're used for the keypad in ESQ1s and the like, where they are
notorious for failing. Eep. Doesn't sound good, eh?"


Seems like the keyboard scanner IC is a known issue with some of  
ENSONIQ products...

does anyone have a 6503 IC for grabs to see if that is the problem?

Are they readily available? Cheap?

Cheers,

Nate


On Apr 16, 2009, at 6:44 PM, Rainer Buchty wrote:

> On Thu, 16 Apr 2009, Kyle Stephens wrote:
>
>> It still does not get past a screen telling me the name, make,  
>> model and OS, as it did before replacing the battery even (even  
>> with a low battery it's supposed to still function). No amount of  
>> button pushing or doing the system reset button combo press has any  
>> effect.
>
> When you remove the battery, does it go past the reset routine?
>
> Usually, the reset procedure is as follows: it is checked for some  
> "magic cookie" of 4 bytes, if that is found, then only the small  
> reset routine is executed (basically initializing the peripherals),  
> otherwise a full factory reset is performed including playing back  
> the factory preset sounds (not present with OS<3.5, with earlier  
> versions you end up with 40x BRASS1).
>
>> Might replacing the EPROMs solve my issues? I can't think of  
>> anything else.
>
> If you are pre-3.5, it's definitely worth an upgrade, even though  
> the no-boot problem should be unrelated.
>
>> Another quirk is a small set of keys are dead for the synth engine,  
>> but work with the MIDI according to Tim. The 3rd G# to the 4th D#  
>> are the offending keys. Tim reckoned one of the diodes in the  
>> scanning matrix are dead, but how would one go about checking that?
>
> That's a cluster of 8. From my experience with those machines, I  
> somewhat doubt that it's diode-related, but rather a defective  
> keyboard controller.
>
> The keyboard is organized in 8 rows of 8 columns. So if you select a  
> row (a cluster of 8 consecutive keys) with a diode tester, you  
> should see a connection to the 8 individual columns: for these you  
> have either the idle column or the pressed column.
>
>> I've the keyboard assembly in front of me now, and it's rather  
>> clever imo - there's two buss wires for measuring the attack time,  
>> as actuated by a small length of fine spring attached to each key,  
>> with the other end soldiered to the diode and so on.
>
> Have a look at
>
> 	http://www.buchty.net/ensoniq/files/esq1-tg/20.jpg
>
> for the schematics of the keyboard control logic.
>
> Rainer
>
>
>
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