[sdiy] ENSONIQ keyboard woes

[Nathan M. Reeves]

so to test the diodes, i dont have to close the switches?

tom mentioned that when we was workin' the polysix diodes he flipped  
it upside down to have the keys pressed then tested....

i guess they can be tested with or without the switch closed?

after leaving the unit on all night and looking at it this morning I  
see (well, feel) that U6 is fairly warm to the touch, though this  
might be normal behavior...

ok i will check the diodes again, also i found out you can lift the  
end of the ribbon cable to expose the terminal leads on them so i  
guess i can check each for continuity....phew

thanks for all the advice if anything its a valuable learning lesson!

cheers

nate

On Jan 22, 2009, at 9:15 AM, cheater cheater wrote:

> Hi Nate,
> *don't* go reseating uC's! you can fry them just like that, by
> touching them, even indirectly. Leave this up to an experienced
> tech... unless you put no value in your item, then feel free to fry it
> :P
>
> Shouldn't a diode (meaning: its terminals) read open in (at least) one
> direction even if it's in a circuit?
> What is the point of holding the keys down?
>
>> How do I read through the archives again? 08^)
> http://img178.imageshack.us/my.php?image=sdiyfw4.jpg
> 8-)
>
> HTH
> D.
>
> On Wed, Jan 21, 2009 at 9:43 PM, Nathan M. Reeves  
> <djservs at comcast.net> wrote:
>> yes it seems like a long shot for the diode check.....
>>
>> i remember the korg polysix thing vaguely....
>>
>> fortunately my DMM has a diode/continuity check built into it
>>
>> its says to:
>>
>> 1. Remove all power from the circuit under test and discharge all  
>> caps.
>> 2. Set to proper selection on switch, looks like a little diode icon.
>> 3. Connect test leads to device you want to check.
>> 4. Reverse test leads and note second reading.
>>
>> If one reading shows a value and the other is over-range (0.F  
>> appears) the
>> device is good.  If 0.F appears during both readings, the device is  
>> open. If
>> both values are very small or zero, the device is shorted.
>>
>> I did this and got 0.F for both readings.... though I am not sure  
>> if the
>> diode I was testing had the key pressed (maybe i will tape all keys  
>> down
>> while i do this...)
>>
>> Tom Wiltshire says
>>
>> "You can buzz them through with a multimeter continuity checker,  
>> assuming it
>> uses enough voltage to overcome the diode drop. Sometimes they  
>> don't. This
>> is why
>>
>> they also include a "diode test" setting on the multimeter. Still,  
>> I've
>> found it easier with an audible clue.
>>
>> I tested a Polysix keyboard by taking it out of the instrument and  
>> lying it
>> down upside down. This meant I could get to the PCB and connector,  
>> but more
>> importantly
>>
>> meant all the keys were pressed down so I could test the diodes. To  
>> avoid
>> the multimeter problem I just mentioned, I tested it with a 9V  
>> battery and a
>> buzzer."
>>
>> what type of buzzer, just one from a PC will do?  i have PLENTY of  
>> those lol
>>
>> so it looks like if its not the diodes, keyboard contacts, nor the  
>> ribbon
>> connector than its most likely the MCU
>>
>> i rather not pull the other MCU i have out of the working one.....
>>
>> Are these obscure and rare  (read expensive) to find?
>>
>> 8^(
>>
>> how do you check the ribbon cable for continuity?
>>
>> What ended up being the problem with your Polysix Tom?  Did you  
>> resolve it?
>>
>> How do I read through the archives again? 08^)
>>
>> Cheers,
>>
>> Nate
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