[sdiy] Ensoniq ESQ-1 Serving Questions

[Rainer Buchty]

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