You must be one of only a few people who are capable of this kind of repair! Very interesting and informative video my friend! One thing I did not understand was why did you measure resistance between ground and +15 V ? I am not an electrical engineer but I do get my share of electrical diagnosis in automotive field. Thanks for your comment and if you don't mind get back to me about the Ohm measurement. I would like to know. 5* Barna
@gavincurtis : No no! I never got a notice that you replied! And with youtube changing, I can't even tell how long ago you replied. On the subject though that is interesting,and I never would have thought about things operating in the other direction of polarity ( if I get that right ). All the best! Barna
you say there are 61 transducers for the keyboard, one for each key....are those just the aftertouch transducers? it looks like there are 2 of those little bumps per key. Is one for the initial velocity sensing and the other for aftertouch, bringing the total to 122?
Wow, lots of desoldering. I'd have been tempted to make a new circuit board. Probably more expensive but my desoldering skills aint so good, I'd have been worried about damaging the board.
@music01234567 Noooo.... many people can repair these as yourself. In the car you have metal chassis and +12V battery or alternator output. In this musical instrument (it's a sexy one), the metal chassis has the earth potential voltage threshold with above and below electrical potential. That means you will have systems operating above and below the ground. To make the old chips work, they provided 8.5 volts and -6.5 volts. My memory is bad, but the 8.5 volt transistors shorted....?
+antigen4 Honestly, I probably over-did it, but no harm as those power rails are shared by 35 more circuit boards upstairs in the synthesizer. The circuitry of this key coder state machine is literally clocked by key strokes, so it has very low transitional state noise. Perhaps this is why they never had caps in the first place by the original engineers in a perfectly health CS-80. But to ensure stability, the .1 (or .01) capacitors between VSS and VDD of each IC should be there and is what I installed. To offset the other possibly ailing bulk filter caps, I wanted a bit more decoupling than necessary.
The Dollar Guy okay thanks for that then... I'd just never seen anyone use such large value caps for the purpose. Still learning the ropes really and have a CS50 i'm thinking of 'cleaning up' so I thought I'd try to see what i could learn from the insides of 'big brother'...
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WOW Way ahead of it's time!!!! that's why it's worth getting restored!
Thanks for posting this!!!
You must be one of only a few people who are capable of this kind of repair! Very interesting and
informative video my friend! One thing I did not understand was why did you measure resistance between ground and +15 V ? I am not an electrical engineer but I do get my share of electrical diagnosis in automotive field. Thanks for your comment and if you don't mind get back to me about the Ohm measurement. I would like to know.
5*
Barna
@gavincurtis : No no! I never got a notice that you replied! And with youtube
changing, I can't even tell how long ago you replied.
On the subject though that is interesting,and I never would have thought about
things operating in the other direction of polarity ( if I get that right ).
All the best!
Barna
Always drop IC sockets in when you can!
In the future when digging up a CS80, they'll conclude the machine was too advanced for its time and therefore was made by Aliens.
you say there are 61 transducers for the keyboard, one for each key....are those just the aftertouch transducers? it looks like there are 2 of those little bumps per key. Is one for the initial velocity sensing and the other for aftertouch, bringing the total to 122?
Wow, lots of desoldering. I'd have been tempted to make a new circuit board. Probably more expensive but my desoldering skills aint so good, I'd have been worried about damaging the board.
@music01234567
Noooo.... many people can repair these as yourself.
In the car you have metal chassis and +12V battery or alternator output.
In this musical instrument (it's a sexy one), the metal chassis has the earth potential voltage threshold with above and below electrical potential.
That means you will have systems operating above and below the ground. To make the old chips work, they provided 8.5 volts and -6.5 volts.
My memory is bad, but the 8.5 volt transistors shorted....?
can i ask why you're using such a huge value for a decoupling cap (100 µF) instead of something like a 10or 22µF?
+antigen4 Honestly, I probably over-did it, but no harm as those power rails are shared by 35 more circuit boards upstairs in the synthesizer. The circuitry of this key coder state machine is literally clocked by key strokes, so it has very low transitional state noise. Perhaps this is why they never had caps in the first place by the original engineers in a perfectly health CS-80. But to ensure stability, the .1 (or .01) capacitors between VSS and VDD of each IC should be there and is what I installed. To offset the other possibly ailing bulk filter caps, I wanted a bit more decoupling than necessary.
The Dollar Guy okay thanks for that then... I'd just never seen anyone use such large value caps for the purpose. Still learning the ropes really and have a CS50 i'm thinking of 'cleaning up' so I thought I'd try to see what i could learn from the insides of 'big brother'...
@music01234567
My response was not mocking you.