[sdiy] ENSONIQ keyboard woes

[cheater cheater]

Nathan:
diodes have leads coming out of them ('legs'). They go out of the
diode and into two holes in the PCB. They are the ones you should be
checking.
If the diode shows up as open both ways, scrape the legs down slightly
to make sure your DMM probes are touching the actual conductor, and
not the layer of metal oxide on those leads.

Cheers
D.

On Thu, Jan 22, 2009 at 3:52 PM, Nathan M. Reeves <djservs at comcast.net> wrote:
> so i should clean the leads on the IC socket or on the ones that the
> keyboard ribbon cable connects to?
> or both?
> cheers
> nate
>
>
> On Jan 21, 2009, at 9:34 PM, Bob Weigel wrote:
>
>> Just glancing...sometimes leads have persistent oxides on them Nathan.   I
>> seldom see dioes actually go totally open but it can happen I guess.
>> Just.. be sure to scrape down leads before you assume that it's really open
>> so you are getting good contact.
>>
>> And some meters have built in buzzers to indicate continuity he probably
>> meant. -Bob
>>
>> Nathan M. Reeves 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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>>>
>>>
>
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