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One thing to test is can your filter self oscillate with the res right up
the resonance feedback is all on chip with the 2044 so if it can do that your chip is bad.
A digital multi meter wont really cut it re testing the correct tool to use is an Oscilloscope.
If you don have one of those....
try bellow methods at your own risk.
Many might disagree with me her and I would like to say be very careful while working this way but I often find that if no oscilloscope is available that simply testing the signal path with a wire attached to the tip of an audio jack will tell you allot.
it is a rather gorilla method and you need steady hands to work this way as if you touch or short out something you shouldn't it could cost you allot more than a SSM 2044.
Audio comes in to pin 1 of the 2044. if you follow this trace from pin one to the first resistor leg it meets you can hold your wire there and see if you here anything
I would recommend having your monopoly arps running in poly mode so you don't have to hit the keys your self.
Also remember that the signal level at this point will be quite different from the final output stage. most likely allot higher so start with the level of your gear quite low to safe guard your speakers and amp.
you should here un-filtered VCOs.
pin 3 is the audio out. test here with the same method. if your chip were working you would here something if not your chip is dead. I suspect the chip is dead anyway. with a dead chip you would still here a slight noise of the final amp envelope open and close when monitoring at high volume as this stage comes after the filter.
remember though 2044s are cheap to get comped to allot of SSM chips so its really worth getting a few installing a socket and swapping out the old one rather than poking around and causing more damage.
--- On
Fri, 28/5/10, chad imes
<likeandrot@yahoo. com>
wrote:
From: chad imes <likeandrot@yahoo. com>
Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!
To: korg_mono-poly@ yahoogroups. com
Date: Friday, 28 May, 2010, 0:21
thanks Alan and Florian!
I'll take pictures of the PCB so you can see.
One point I'm still not clear on is how I might test the output of the SSM 2044 and the 2033s. Can that be done with a DMM or in another easy cheap way
thank you very very much!!!
chad
From:
Alan Dicker <alanmdicker@
yahoo.co
. uk>
To:
korg_mono-poly@ yahoogroups. com
Sent:
Thu, May 27, 2010 11:09:43 PM
Subject:
Re: [korg_mono-poly] ...and all of the sudden, no sound!
|
got any pictures
it may be that the pads have carodid to the piont wher the metirial don;t conduct properley or it might be just that the surface is to uneaven to give good contact over the the pad. testing the curcuit by simply holding a wier over the connection in place of the rubber pad might help you determin of the pads non conductive any more but as Florain said it may be the associated diode thats faild. those diodes are very cheap parts to get.
I take it the board and rubber contacts have all been cleaned in the past
--- On
Thu, 27/5/10, chad imes
<likeandrot@yahoo. com>
wrote:
From: chad imes <likeandrot@yahoo. com>
Subject: Re: [korg_mono-poly] ...and all of the sudden, no sound!
To: korg_mono-poly@ yahoogroups. com
Date: Thursday, 27 May, 2010, 13:18
it's the PCB that's corroded somehow -like the previous owner spilt a soft drink on it or something
Soooo, is it possible to check these things using a DMM
0_o That's all I got.
thanks again,
chad
From:
Florian Anwander <fanwander@mnet-
online.de
>
To:
korg_mono-poly@ yahoogroups. com
Sent:
Thu, May 27, 2010 8:39:38 PM
Subject:
Re: [korg_mono-poly] ...and all of the sudden, no sound!
Hi Alan
> From your description it sounds like you filter chip SSM2044 may have
> gone.
first he should check whether there is a signal at pin 1 (input) of the
SSM2044
Also it is worth checking the four ICs 2033 at pin 8, 3 and 12 whether
there is a signal.
> mean it seems that the rubber contact has corroded or the PCB contact
> You night find the rubber strips on ebay. same type as in the polysix
> and another few keyboards. as for finding a complete keyboard PCB that
> might be more tricky.
check also
http://www.oldcrows.net/~oldcrow/synth/korg/polysix/keyclean.html
If the contacts don't work ever, then maybe also some of the diodes in
the keyboard matrix might have died.
Florian
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