Vintage Synth Repair

Replace the contact strips, they are the same as any Fatar keybed.  Fatar only made the keybed assembly.  


Modern keyboards use a X/Y matrix or row and column matrix, as do computer keyboards.    The diodes are there to isolate keys of the same row from keys of another column.  An open diode (D2) would cause no note on for that key or full velocity (D1) depending on whether D1 or D2 was open. 


If either diode for that key was shorted, you  would have no problem with that key. But if any key in that row or multiples of eight were down with the one with the shorted diode key down, then you would have a problem.  


Example: If C4 has a shorted diode then if E3 or G#4 were key down too, you would have no isolation between the data lines of the  key scan circuit.  So all two key combinations that work correctly and do not contain the suspect key would be good and any combination including the key with the suspect shorted diode would exhibit the problem. 

Another example of keys sharing a row: D1, A#1, F#2, D3, A#3, F#4, D5, etc. Or count up or down 1-8, then repeat.


A word about using an Alesis contacts circuit board(made by FATAR too) in another manufactures keyboard that appears to used the same circuit board, the diodes are reversed.  




>________________________________
> From: brian dampier <brianmann01@...>
>To: "vintagesynthrepair@yahoogroups.com" <vintagesynthrepair@yahoogroups.com> 
>Sent: Wednesday, June 27, 2012 10:00 AM
>Subject: Re: [vintagesynthrepair] Re: Alesis QS8  Note E 2 loses volume after 1 to 3 presses.
> 
>
>  
>Hey Fran, 
>The first thought when I bought it was to reset it and I have done that a couple of times. I should mentioned that. But thanks for the input.( BTW I did not realize the mod wheel should be rotated to zero. Thanks again.) 
>
>
>From: narfman96 <narfman96@...>
>To: vintagesynthrepair@yahoogroups.com 
>Sent: Wednesday, June 27, 2012 12:19 PM
>Subject: [vintagesynthrepair] Re: Alesis QS8  Note E 2 loses volume after 1 to 3 presses.
> 
>
>  
>Another quick thing to try is reset your QS. I have seen them do really weird things. You would swear (literally) that the synth was toast and the reset would solve it.
>
>1. Turn the power off.
>2. Make sure the Mod Wheel is all the way down, otherwise the zero position of the wheel will be incorrect.
>3. Hold down the 0 and 3 buttons while turning the power on.
>The unit will come on showing Program 01 with * in the display and no program name. This is the Program Mode edit buffer. It is a good place to start creating a program from scratch because all the parameters are set to their default settings. Re-initializing will also reset all global parameters. Re-initializing will not change any of the Mix or Programs in the unit.
>
>Good luck, Fran
>
>--- In mailto:vintagesynthrepair%40yahoogroups.com, brian dampier <brianmann01@...> wrote:
>>
>> Nope, no stuck notes but the diode sounds like a place to look. Thanks for the input. 
>> 
>> 
>> 
>> ________________________________
>>  From: jammie <jammie.emma@...>
>> To: mailto:vintagesynthrepair%40yahoogroups.com 
>> Sent: Wednesday, June 27, 2012 10:54 AM
>> Subject: Re: [vintagesynthrepair] Alesis QS8  Note E 2 loses volume after 1 to 3 presses.
>> 
>> 
>> 
>> Â  
>> 
>> 
>> bad diode for that key on the contact board is the 
>> only surgestion i can give 
>> Â  
>> as you are not having this problem on any other key 
>> Â  
>> do you also get stuck notes when pressing this 
>> key 
>> Â  
>> never heard a qs-8 doing it 
>> Â  
>> but have had this happen on esq1 mirage sq1 
>> Â  
>> emu emax 1/2 
>> ----- Original Message ----- 
>> >From: brianmann01 
>> >To: mailto:vintagesynthrepair%40yahoogroups.com 
>> >Sent: Wednesday, June 27, 2012 2:46  PM 
>> >Subject: [vintagesynthrepair] Alesis QS8  Note E 2 loses volume after 1 to 3 presses. 
>> >
>> >Â  
>> >Hi Everyone, 
>> >Its an ALesis QS-8 weighted keys. ( I think Fatar is the 
>>   maker). It works perfect except that E2 will lose volume after being played 1 
>>   to 3 times after power up. The condition will repeat each time I power down 
>>   and back up. The problem also affects the MIDI modules. 
>> >What I have done 
>>   thus far
>> >1. Removed the contact boards and cleaned the carbon impregnated 
>>   contacts on the double bubble strip
>> >2. cleaned the contact points on the 
>>   board. 
>> >3. Cursed a lot after trying this 3 times. 
>> >
>> >It seems like 
>>   its a voltage drop.I am not sure as I am not as electronically savvy as I like 
>>   to think. No one anywhere has posted a similiar problem that I can find. 
>> >There are 2 contact PC boards. The entire unit is in pristine condition 
>>   and there is no evidence of damage. 
>> >
>> >It drives me nuts as its exactly 
>>   right 1 to 3 plays and than it drops no other keys have this problem. Your 
>>   input about my output is appreciated. Thanks. Brian 
>> >
>> >
>>
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