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Proper LSI values on Kas Board-Sharing project

 


Hello CS80 users,

Probably as most CS80 owners, i am aware that the most critical parts in the beast are the 2 main LSI's (YM26600&Ym26700), as their failure could quickly become problematic, since they are Yamaha proprietary and for this reason, hard to find/replace.And because they are the brain of the system, i guess it's important to rely on them in first place, before doing any other work/check further in the synth.
That's why i decided to check mine, and for this purpose i focused on the values that i should expect on their respective 40pins.For this i collected infos from the CS Series servicing guide, CS80 service manual, and CS80 tuning&adjustment procedure, but unfortunately without concluding to a definitive and complete list of 'proper values'.Of course i also completed that list with some tangible results collected from my own CS80, but i prefered to leave a question mark in those places where my own CS80 results seemed hazardous.

Maybe some of you could advice me in the process? My intend is to create ultimately a visual map of the LSI's of the most important boards, starting with the KAS for now.The idea is to share all results in this forum for everybody's convenience, so any help is welcome!

So, this is what i could find (question marks stand for unknown values, and in parenthesis are my own CS80 values, filling missing infos from the manuals):

1) LSI YM26600:
-VSS (Pin#1)= +8.5v
-Master Clock (Pin#2)= 94Khz (~5khz)
-SC (Pin#3)= 1/9 of 94Khz= 10.8Khz
-SC8 (Pin#4)= 1/8 of 10.4Khz= 1.35 Khz
-IC (Pin#5)= ?
-VDD (Pin#6)= -6.5v
-Note terminals (Pin#7-19)= ?
-U1-U5 (Pin #20-25) = ?
-N1-N4 (Pin #25-28) = ?
-B1-B3 (Pin #29-31)= ?
-K01-K08 (Pin #32-39)= +8.5v/-6.5v (Note off/Note on)
-MODE (Pin #40)= -6.5v/+8.5v (8 sounds/7 sounds)

2) LSI YM26700:
-VSS (Pin#1)= +8.5v
-SC8 (Pin#2)= 1.35 Khz (=Pin#4 YM26600)
-PORT (Pin#3)= -6.5v/+8.5v (PN3-VR2 short/long)
-PC (Pin#4)= ?
-N1-N4 (Pin#5-8)= ?
-B1-B3 (Pin#9-11)= ?
-Pin#12= 10.4Khz
[-Pin#13=125mv
-Pin#14= 250mv
-Pin#15= 500mv
-Pin#16= 1v
-Pin#17= 2v
-Pin#18= 4V
-Pin#19-30 (C0/C5)=190mv/1.97v-202mv/2.1v-214mv/2.22v-227mv/2.35v-240mv/2.49v-255m/2.64v-270mv/2.80v-286mv/2.97v-303mv/3.14v-321mv/3.33v-340mv/3.53v-361mv/3.75v]
-Pin#31-38= ?
-pin#39= -6.5v
-Pin#40= 94Khz

Thank you for your help!
 

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? There is a complete analysis of the custom chips in the Yamaha CS Servicing Guide.? I used this book to work out IG series equivalent circuits a dozen or so years back.? It covers the YM parts too.? There was a pdf of it up somewhere....yeah, here:



Crow
/**/

On 3/1/2015 7:17 PM, gearfire01@... [yamahacs80] wrote:


Hello CS80 users,

Probably as most CS80 owners, i am aware that the most critical parts in the beast are the 2 main LSI's (YM26600&Ym26700), as their failure could quickly become problematic, since they are Yamaha proprietary and for this reason, hard to find/replace.And because they are the brain of the system, i guess it's important to rely on them in first place, before doing any other work/check further in the synth.
 

What is your objective here?? I've had a few of them fail on me.? The most common symptom of failure is the top octave not responding.?

-Mike
http://borishelectronics.com
 

Thank you Crow, actually i did mention that one in my sources for collecting infos, but indeed i didnt go thru all the detailed explanations about the LSI's functions...It is true that i opted for a quicker approach like just listing values, but surely it's a bit more complex than just that.
Gonna go into it deeper tonight, and collect more infos for sure that way :-)

About those IG series circuits, did you manage to get what you hoped for?

best
 

Hello Mike,

Actually i've been reading about -6.5v/+8.5v (1/0) process almost everywhere in the manuals, and precisely this is what pushed me to really check the KAS LSI's, ?when i realized my TR1-TR8 didnt follow those values (I have more -4v/+6v).
So, i checked the?26600 and 26700, and there again i couldnt find -6.5v/+8.5v values everywhere, instead
i got a few confusing values here and there:

YM26600
- Note terminals (Pins 7-19)= +2.3v(Note on) / -3.8v(Note off)
- U1-U5 (Pins 20-24)= +2.5v(Note on) / +8.4v(Note off)
- N1-N4 and B1-B3: Inconstant results...Probably need to read more about LSI functions first to get the logic
?-All other values seem to be ok

YM26700
-CH1 (Pin 38)= 1v (stuck from lowest C to highest C)
-N1-N4 and B1-B3: Inconstant results...same as above
?-All other values seem to be ok

KAS Board?
TR1-TR8= -4.3v(Note on)?/ 5.5v(Note off)
TR9= -3.7v

At least, the top octave (i guess U5) is responding something ;)

Great if it inspires you something to start with! :-)

Thank for the help,

Luca

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