The higher value caps were available and are used in other places in the keyboard, so cost and size were not an issue. Engineering team probably determined they didn't need larger values. They are most likely correct. The DC voltage rails are critical on this board for the hold amplifiers to be absolutely stable. So I opted for larger value capacitors to give a little extra headroom. The DC rails are shared by many other systems.
@cumesoftware They fit quite well actually. In the video the new pot pins look much farther apart, but the body of the pots fit flush against the board. No modifications to the board.
@Andrij09 Hi. Most of them are Mylar on that board. The large green sample and hold units, I couldn't determine if Mylar or Polypropylene. Most of the green capacitors like that from the 70-80's were Mylar. Regardless, they have been replaced with high precision Polypropylene units that are designed for pulse and sample and hold application. On the KAS board, a mylar had drifted value of about 35%. Keyscan oscillator was 60 Khz, supposed to be 95-100Khz. Replace with polyprop and at 97Khz
Stability should be a working synth. I am replacing rotted capacitors in the power supply and in all digital timing and pulse generator circuits which need to be stable (as intended). The etheric magic of this machine is from the 16 independent oscillators that will NOT be modified. But temperature and transport stability will be improved. My CS80 will not become a digital brick as some seem to think.
The 3rd and 4th octave were mute on the keyboard after I made a stupid mistake. Lowered the upper voice card rack with the power still on and shorted +15V into the keyboard detector switches. All of the key switches go into the 26600! I removed the 26600 and the 26700 to breadboard them separately so I could verify if they were okay. I was so very lucky. I put the sockets there to avoid stressing the IC's again. Normally you do not need sockets. The 26600 is apparently a very rugged LSI.
@ezquimal Next video where I rebuild the KAS board I get the lower 2 octaves working and I play. Editing that video but editing computer failed. Video will be here soon.
@gavincurtis Hi Gavin, I've a CS60 which is working pretty well except for one problem. It's stuck on Sustain II mode even when the switch is moved to sustain I. (ie, the note stealing is permanently on). Apart from the switch itself which I think is fine, could you suggest what else can be checked to see why it's stuck in Sustain II mode?
@cumesoftware Hi, Thanks for posting. The parts are extremely high quality. But manufacturing processes and materials of today surpass that of nearly 40 years ago... making more precise and reliable components. Worst part of the CS-80 are the single turn carbon trimmers. If Yamaha used multiturn pots, nobody could afford this keyboard. Digital tuning is also very difficult as this is an extremely complex analog synthesizer. Been working on microprocessor digital tuning retrofit. but damn.
1:03 with a ancient prize like that I would do MY BEST to match replacement components. No just Hope on a lark. They Have Values for a reason! I guess.
How common is it for mylar caps to drift out of spec? I recently replaced most of the electrolytics in my Roland Jupiter-4 and I'm wondering if maybe the mylar caps should be tackled next.
there is only one sample and hold board on this synth? is it used just for the noise generator? the cs-80 doesn't have a random LFO like the Jupiter8 does it?
Nice work, but it looks to me not logical to replace the trimmer pots by measuring there values.They look good quality to me ( ceramic ? ) and are sealed, but most important they are calibrated at the default values of the older components, witch you are replacing.So I always recalibrate them. .
These are indeed ceramic substrate trimmers. About 50 or so of this type. The remaining 500 or so trimmers in the keyboard are carbon and most are off by 30-40+% . That is a 100K trimmer will read as little as 65K to over 130K. But these ceramics are dead on. BUT.... they are difficult to get the calibration offset for the op amp dead on and a part of me felt guilt replacing an existing high quality part which was perfectly stable once tweaked in. Going to a quality sealed multi-turn made calibrating offset very easy so I made the decision to replace them. Pre-adjusting as I did in the video just ensures the keyboard remains playable as is, but really do require a final calibration as assuredly they needed it beforehand. Since I was replacing all trimmers in the entire keyboard with multi-turn, I replaced these. Even with multi-turn, some calibrations are still very sensitive in other parts of the keyboard, but remain stable unlike the carbon trimmer "humidity sensors" as I like to call them. Now the older components such as the metal can precision op amps in this sample and hold board and other parts of the synth, I do not change them as I have never encountered a bad one and they are "aged" aka stable and do not suffer from issues as the old 4000 series chips. The sample and hold capacitor I use has much less leakage vs the original and within 2% vs a much wider tolerance of the originals which I believe is 10%. One thing that amazes me, the 5% carbon Japanese made carbon film resistors..... ALL within 1%... more like 0.5%. Amazing quality. However, they are using carbon composition resistors for 3.3M, 4.7M and 10 meg-ohm in the keyboard; in critical areas that are off by up to 40%! Very critical ones that set filter crossover are usually way off. The 10M resistors that are trimmed with 100K pots in the mixer sections of the tremolo/chorus stereo effects board typically read 14 or more megohms. Way out of specification which is probably why tremolo/chorus system sounds so unsuitably bad on many CS-80s today.
Yes, but I saw you not making the adjustments, so I was wondering.It surprise me that the carbon resister good be way off there value,that's a point to look at.Hope to see more vids of the restoration of this beast, keep up the good work!
@hartleytransform Hey there, I'm working on a CS60 at the moment and it intermittently has the same problem. I'll debug and if you send me a message i will reply with the detail.
The higher value caps were available and are used in other places in the keyboard, so cost and size were not an issue. Engineering team probably determined they didn't need larger values. They are most likely correct.
The DC voltage rails are critical on this board for the hold amplifiers to be absolutely stable. So I opted for larger value capacitors to give a little extra headroom. The DC rails are shared by many other systems.
@cumesoftware They fit quite well actually. In the video the new pot pins look much farther apart, but the body of the pots fit flush against the board. No modifications to the board.
Thanks.
It partially works (whenever it wanted to), which is why it is being restored. In the KAS video, you will get to hear it.
@Andrij09 Hi. Most of them are Mylar on that board. The large green sample and hold units, I couldn't determine if Mylar or Polypropylene. Most of the green capacitors like that from the 70-80's were Mylar.
Regardless, they have been replaced with high precision Polypropylene units that are designed for pulse and sample and hold application.
On the KAS board, a mylar had drifted value of about 35%. Keyscan oscillator was 60 Khz, supposed to be 95-100Khz. Replace with polyprop and at 97Khz
Nice move installing sockets for the chips when you can.......if it ever comes back to you. easy to test and diagnose chip faults.
Stability should be a working synth. I am replacing rotted capacitors in the power supply and in all digital timing and pulse generator circuits which need to be stable (as intended).
The etheric magic of this machine is from the 16 independent oscillators that will NOT be modified. But temperature and transport stability will be improved. My CS80 will not become a digital brick as some seem to think.
Thank you so much for all of this wonderful info! Did part 7 get misplaced some where? I'm trying to find it. I see part 8. ;-)
Another great video! I really look forward to each one and they are very educational for me. Keep them coming!
@fourbarposer And just in case, all removed parts are organized/saved in order to put everything back to before.
The 3rd and 4th octave were mute on the keyboard after I made a stupid mistake. Lowered the upper voice card rack with the power still on and shorted +15V into the keyboard detector switches. All of the key switches go into the 26600! I removed the 26600 and the 26700 to breadboard them separately so I could verify if they were okay. I was so very lucky. I put the sockets there to avoid stressing the IC's again. Normally you do not need sockets. The 26600 is apparently a very rugged LSI.
ottimo
@ezquimal Next video where I rebuild the KAS board I get the lower 2 octaves working and I play.
Editing that video but editing computer failed. Video will be here soon.
I tell you though. I wouldn't mind replacing components ALL DAY!!!! I think it's cool!!!
Hi.I want more vids...do you have more?
You are great
@gavincurtis Hi Gavin, I've a CS60 which is working pretty well except for one problem. It's stuck on Sustain II mode even when the switch is moved to sustain I. (ie, the note stealing is permanently on). Apart from the switch itself which I think is fine, could you suggest what else can be checked to see why it's stuck in Sustain II mode?
@ezquimal video of me playing is now on youtube.
because it blew fuses and couldn't be played until one final IC on the KAS board was replaced.
@aidabab
It's called a vacuum desoldering tool.
when can see a video with you playing this instruments?
were the higher uF caps not available back in the 80s when these were being built? Is that why they did not use them, or was it just a money issue?
@cumesoftware
Hi, Thanks for posting. The parts are extremely high quality. But manufacturing processes and materials of today surpass that of nearly 40 years ago... making more precise and reliable components.
Worst part of the CS-80 are the single turn carbon trimmers. If Yamaha used multiturn pots, nobody could afford this keyboard.
Digital tuning is also very difficult as this is an extremely complex analog synthesizer. Been working on microprocessor digital tuning retrofit. but damn.
1:03 with a ancient prize like that I would do MY BEST to match replacement components. No just Hope on a lark. They Have Values for a reason! I guess.
How common is it for mylar caps to drift out of spec? I recently replaced most of the electrolytics in my Roland Jupiter-4 and I'm wondering if maybe the mylar caps should be tackled next.
there is only one sample and hold board on this synth? is it used just for the noise generator? the cs-80 doesn't have a random LFO like the Jupiter8 does it?
Gavin, are there more instalments?? Or did you only make 6 videos in this series?
i saw on the PPG fan site that you are the only US dealer that can service a PPG Wave. How often do you fix those?
Nice work, but it looks to me not logical to replace the trimmer pots by measuring there values.They look good quality to me ( ceramic ? ) and are sealed, but most important they are calibrated at the default values of the older components, witch you are replacing.So I always recalibrate them. .
These are indeed ceramic substrate trimmers. About 50 or so of this type. The remaining 500 or so trimmers in the keyboard are carbon and most are off by 30-40+% . That is a 100K trimmer will read as little as 65K to over 130K. But these ceramics are dead on. BUT.... they are difficult to get the calibration offset for the op amp dead on and a part of me felt guilt replacing an existing high quality part which was perfectly stable once tweaked in. Going to a quality sealed multi-turn made calibrating offset very easy so I made the decision to replace them. Pre-adjusting as I did in the video just ensures the keyboard remains playable as is, but really do require a final calibration as assuredly they needed it beforehand. Since I was replacing all trimmers in the entire keyboard with multi-turn, I replaced these. Even with multi-turn, some calibrations are still very sensitive in other parts of the keyboard, but remain stable unlike the carbon trimmer "humidity sensors" as I like to call them. Now the older components such as the metal can precision op amps in this sample and hold board and other parts of the synth, I do not change them as I have never encountered a bad one and they are "aged" aka stable and do not suffer from issues as the old 4000 series chips. The sample and hold capacitor I use has much less leakage vs the original and within 2% vs a much wider tolerance of the originals which I believe is 10%. One thing that amazes me, the 5% carbon Japanese made carbon film resistors..... ALL within 1%... more like 0.5%. Amazing quality. However, they are using carbon composition resistors for 3.3M, 4.7M and 10 meg-ohm in the keyboard; in critical areas that are off by up to 40%! Very critical ones that set filter crossover are usually way off. The 10M resistors that are trimmed with 100K pots in the mixer sections of the tremolo/chorus stereo effects board typically read 14 or more megohms. Way out of specification which is probably why tremolo/chorus system sounds so unsuitably bad on many CS-80s today.
Yes, but I saw you not making the adjustments, so I was wondering.It surprise me that the carbon resister good be way off there value,that's a point to look at.Hope to see more vids of the restoration of this beast, keep up the good work!
@hartleytransform
Hey there,
I'm working on a CS60 at the moment and it intermittently has the same problem. I'll debug and if you send me a message i will reply with the detail.
@gavincurtis ..otherwise known as a 'solder sucker'