I have found an EKOsynth 15 that's available for a pretty nice price, with one catch - the main DCO board is missing.
It was probably cannabilised by someone who had a nicer looking unit whose own board died (this particular example has a few blemishes and some slider knobs missing. I can live with that).
It's a cosmically stupid idea to rebuild the main board, right? I would have help from professors in my college - they'd probably laugh and shake their heads at me in a sort of, "what has he done now," sort of way, but they would help nonetheless xD.
The schematic and layout can be found here on synthxl. The main thing I'm concerned about are the mystery ICs that don't give me anything back when I search them online. They probably have something to do with the 'Digital' part in DCO. If they're irreplaceable and/or preprogrammed in some way, I'm snookered. If not, the rest is just mainly just some transistors and OTAs - moog stuff through and through, basically. Nothing that hasn't been D.I.Y.'d before.
So - what do y'all think? 😆😀
Thanks in advance for any help!
It was probably cannabilised by someone who had a nicer looking unit whose own board died (this particular example has a few blemishes and some slider knobs missing. I can live with that).
It's a cosmically stupid idea to rebuild the main board, right? I would have help from professors in my college - they'd probably laugh and shake their heads at me in a sort of, "what has he done now," sort of way, but they would help nonetheless xD.
The schematic and layout can be found here on synthxl. The main thing I'm concerned about are the mystery ICs that don't give me anything back when I search them online. They probably have something to do with the 'Digital' part in DCO. If they're irreplaceable and/or preprogrammed in some way, I'm snookered. If not, the rest is just mainly just some transistors and OTAs - moog stuff through and through, basically. Nothing that hasn't been D.I.Y.'d before.
So - what do y'all think? 😆😀
Thanks in advance for any help!
Well, it would be a big project, but not impossible. There are several ways to go about this that mostly depend on the intended use of the synth. You have a 45 year old synth with a missing circuit board. I have never seen one of these, so I don't know what it actually looks like inside.
If you want to restore it to original condition, you will need to find another board or make an exact duplicate of the missing board. Either way someone with the skill set to lay out and make, or have made, that board. This assumes that all the 45+ year old parts can be found. It looks like the board plugs into some kind of card edge connector, so the connection points need to be designed into the board.
If you just want to make it work so that you can use it, you would still need to create a circuit board, perf board build, or other method of duplicating the original circuitry, and a method of connecting it into the rest of the synth without causing damage to a 45 year old device in unknown condition. This could be done by removing the original connector and substituting something else, or direct connection from the original wiring to a newly designed board. The original wire in something that old may be quite brittle. Now you need someone who has repaired vintage stuff before, and someone who could lay out a new board.
Both of these routes require finding sources for all of the 45 year old chips. This may NOT be the hardest part. All of the chips that start with the number 4 are generic CMOS logic chips made by Motorola and RCA in the 70's. I worked for Motorola for 45 years and built synths in my spare time, so I recognized the numbers. The original Motorola numbering system put a MC1 in front of the 4000 number and some letters after it. The original RCA numbering system used CD in front of the 4000 number with different letters after it. So, IC1, the 4046B is a Motorola MC14046B or an RCA CD4046B. Neither Motorola or RCA are still in the IC manufacturing business today. Fortunately, these chips were such a big hit that they are still being made today by Texas Instruments and others. Finding them is easy. Open up Mouser Electronics's web side and select Semiconductors / Integrated Circuits. Then insert CD4046 or which ever one of the 4000 and 4500 series chips you are looking for, then choose through hole, unless you choose to do an SMD board for size reduction.
This leaves a few other chips. The SAA1005 is a divider chain designed especially for electronic organs and synths. They are not currently made, but can occasionally be found on the surplus market or some synth builder sites. You could also use a chain of 7 flip flops to perform the same function. My string ensemble clone used a single CMOS chip that had 7 flip flops in a chain that worked. Vaguely I remember the number CD4024, but I may be wrong. It's been a long time ago.
The Chip marked S50242 is a top octave generator chip made by Mostek who went out of business long ago. Their number was MK50242 There were three different versions of this chip with the MK50240 being the most common. it differs from the MK50242 only in pin configuration. Either would work here but the 50240 would require a minor board layout change.
The old CA3080 chip went extinct years ago, but has recently been reissued by Alfa RPAR in Latvia. It's now the AS3080 and available from the synth builder sites like Synthcube and Cabin Tech Global.
The 74LS221 and LM348 are both common chips.
The third possibility would be to use an Arduino or compatible board (I prefer the TEENSY) to emulate all of this, but you would need someone versed in software coding.
Note that the DCO board does generate the raw music wave form, but it has other functions. The keyboard used in this synth is a matrix design. The matrix is scanned by the logic on the lower right of the schematic. The upper right is the master clock for the top octave generator (chip P) the played note is selected by chips N, O and H, while the actual VCO is buried inside Chip A. Chips CD and B select the octave. The lower left of the schematic is voicing, and the upper left is the LFO.
If you want to restore it to original condition, you will need to find another board or make an exact duplicate of the missing board. Either way someone with the skill set to lay out and make, or have made, that board. This assumes that all the 45+ year old parts can be found. It looks like the board plugs into some kind of card edge connector, so the connection points need to be designed into the board.
If you just want to make it work so that you can use it, you would still need to create a circuit board, perf board build, or other method of duplicating the original circuitry, and a method of connecting it into the rest of the synth without causing damage to a 45 year old device in unknown condition. This could be done by removing the original connector and substituting something else, or direct connection from the original wiring to a newly designed board. The original wire in something that old may be quite brittle. Now you need someone who has repaired vintage stuff before, and someone who could lay out a new board.
Both of these routes require finding sources for all of the 45 year old chips. This may NOT be the hardest part. All of the chips that start with the number 4 are generic CMOS logic chips made by Motorola and RCA in the 70's. I worked for Motorola for 45 years and built synths in my spare time, so I recognized the numbers. The original Motorola numbering system put a MC1 in front of the 4000 number and some letters after it. The original RCA numbering system used CD in front of the 4000 number with different letters after it. So, IC1, the 4046B is a Motorola MC14046B or an RCA CD4046B. Neither Motorola or RCA are still in the IC manufacturing business today. Fortunately, these chips were such a big hit that they are still being made today by Texas Instruments and others. Finding them is easy. Open up Mouser Electronics's web side and select Semiconductors / Integrated Circuits. Then insert CD4046 or which ever one of the 4000 and 4500 series chips you are looking for, then choose through hole, unless you choose to do an SMD board for size reduction.
This leaves a few other chips. The SAA1005 is a divider chain designed especially for electronic organs and synths. They are not currently made, but can occasionally be found on the surplus market or some synth builder sites. You could also use a chain of 7 flip flops to perform the same function. My string ensemble clone used a single CMOS chip that had 7 flip flops in a chain that worked. Vaguely I remember the number CD4024, but I may be wrong. It's been a long time ago.
The Chip marked S50242 is a top octave generator chip made by Mostek who went out of business long ago. Their number was MK50242 There were three different versions of this chip with the MK50240 being the most common. it differs from the MK50242 only in pin configuration. Either would work here but the 50240 would require a minor board layout change.
The old CA3080 chip went extinct years ago, but has recently been reissued by Alfa RPAR in Latvia. It's now the AS3080 and available from the synth builder sites like Synthcube and Cabin Tech Global.
The 74LS221 and LM348 are both common chips.
The third possibility would be to use an Arduino or compatible board (I prefer the TEENSY) to emulate all of this, but you would need someone versed in software coding.
Note that the DCO board does generate the raw music wave form, but it has other functions. The keyboard used in this synth is a matrix design. The matrix is scanned by the logic on the lower right of the schematic. The upper right is the master clock for the top octave generator (chip P) the played note is selected by chips N, O and H, while the actual VCO is buried inside Chip A. Chips CD and B select the octave. The lower left of the schematic is voicing, and the upper left is the LFO.
Wow, that is a truly incredible amount of information! I think that tells me what I need to know in order to take a crack at this! Thanks so much for your input 👍
Thanks so much for your help and knowledge. I'll of course be posting on this board if I get it working.
Regards.
From what I can see, the original connector is just a strip of metallic pins with with wires soldered to discrete points on individual boards. This results in a truly horrendous amount of wire!
Thanks so much for your help and knowledge. I'll of course be posting on this board if I get it working.
Regards.
I have some CA3080 in my stock. The others I have none, I tossed over 10 keyboards, from the seventies up to 2000, some years ago. Repairing them costs more then a new one. So no luck for the other parts. Let me know where to send them. If you pay the postal service it's ok. You can PM me but let me know via the forum.
That's very true. I do only need one, however, and I would feel bad for depleting someone's stock of them when I don't have to haha.
I was thinking that as well. The schematic includes both front and back traces, I think, based on the colour code.
Yeah, the artwork is all standard practice that someone skilled in the craft can duplicate.
The layout of all these old pcbs were done by hand. No computer anything.
Of course, the scale must be set correctly. Fortunately the resolution of the file is very good.
If you're actually going to make all this effort, not having a number of spares would be rather foolish.
The layout of all these old pcbs were done by hand. No computer anything.
Of course, the scale must be set correctly. Fortunately the resolution of the file is very good.
If you're actually going to make all this effort, not having a number of spares would be rather foolish.
There are two packages for the CA3080 and more than one vendor, though in the 70's they were probably made in the old RCA facility. There are CA3080 chips in a round metal can with wire leads, and in a plastic 8 pin DIP. In theory they should all have the same die inside. I bought a used first gen whiteface ARP Odyssey cheap, from a guy who had sent it back to ARP two or three times for the same complaint. It had an ever increasing level of background hiss that grew louder with every minute that it was on. It was still in the shipping case where it had recently been back to ARP. The owner had bought a MiniMoog which he took back to college leaving his parents to sell the ARP.
It worked good for a while, but within a few months became noisy so I opened it up. It was obvious that the round metal can CA3080 had been changed, probably more than once since there was minor PCB damage in that area and no obvious repair work anywhere else in the unit. Wanting to fix it quickly, I swapped the noisy CA3080 in the VCA with an unknown chip in the sample and hold circuit. The synth worked again but became noisy within a few weeks. Digi Key was a small time operation in the 70's catering mostly to hobbyists and small scale computer builders. They only had 8 pin DIP CA3080s so I bought a few and sky wired two of them into the Odyssey. It worked flawlessly until I was stupid enough to sell the Odyssey, the ARP "Little Brother" SEM, and an early vintage Univox Mini Korg way too cheap in the digital 90's when I was rocking a DW8000.
The RCA chip division merged with Intersil and both were later acquired by Harris so you can find round metal can CA3080's with all three brands on them. I have seen other brands on the 8 pin DIP but don't remember which ones, nor do I know if the CA3080 was ever made in SMD. Why did the round metal chips fail in the Odyssey, but the 8 pin dips survive? I don't know. I have not used the new production AS3080, but Alfa RPARs other reissue synth chips do work good.
It worked good for a while, but within a few months became noisy so I opened it up. It was obvious that the round metal can CA3080 had been changed, probably more than once since there was minor PCB damage in that area and no obvious repair work anywhere else in the unit. Wanting to fix it quickly, I swapped the noisy CA3080 in the VCA with an unknown chip in the sample and hold circuit. The synth worked again but became noisy within a few weeks. Digi Key was a small time operation in the 70's catering mostly to hobbyists and small scale computer builders. They only had 8 pin DIP CA3080s so I bought a few and sky wired two of them into the Odyssey. It worked flawlessly until I was stupid enough to sell the Odyssey, the ARP "Little Brother" SEM, and an early vintage Univox Mini Korg way too cheap in the digital 90's when I was rocking a DW8000.
The RCA chip division merged with Intersil and both were later acquired by Harris so you can find round metal can CA3080's with all three brands on them. I have seen other brands on the 8 pin DIP but don't remember which ones, nor do I know if the CA3080 was ever made in SMD. Why did the round metal chips fail in the Odyssey, but the 8 pin dips survive? I don't know. I have not used the new production AS3080, but Alfa RPARs other reissue synth chips do work good.
With due respect, the possible odds against it are huge.
First the need for a perfect PCB clone, which is "doable" of course, but WHO will?
Kudos to your Professors and no doubt they will try to help, but in general most (all?) PCB designers nowadays start with a schematic which then is more or less automatically turned into a PCB artwork.
This requires having all part "footprints" available.
Not a given, at all, for old stuff and even less on proprietary ICs.
The alternative is to print large size, (and I mean newspaper size or almost) board layer images (guess top and bottom) , tape them to the wall, and have somebody to lay them out by hand, "as if" he was using black crepe tape on mylar {70s 80s state of the art method), only on screen instead of "on a table".
Which is how the original was made.
Again, "doable" ... but will somebody have the expertise and free time for that?
Maybe a retired or close to retiring "greybeard" could, just for "good old times" sake 😄
First the need for a perfect PCB clone, which is "doable" of course, but WHO will?
Kudos to your Professors and no doubt they will try to help, but in general most (all?) PCB designers nowadays start with a schematic which then is more or less automatically turned into a PCB artwork.
This requires having all part "footprints" available.
Not a given, at all, for old stuff and even less on proprietary ICs.
The alternative is to print large size, (and I mean newspaper size or almost) board layer images (guess top and bottom) , tape them to the wall, and have somebody to lay them out by hand, "as if" he was using black crepe tape on mylar {70s 80s state of the art method), only on screen instead of "on a table".
Which is how the original was made.
Again, "doable" ... but will somebody have the expertise and free time for that?
Maybe a retired or close to retiring "greybeard" could, just for "good old times" sake 😄
If I were doing this, I would enlarge the pdf artwork to exactly the right size, print it out,
and use a light table to lay it out with tape. That stuff may be still made, and is on ebay as NOS.
There also may also be a way to do this with software. but the two layers are superimposed in one image,
which could cause a problem.
and use a light table to lay it out with tape. That stuff may be still made, and is on ebay as NOS.
There also may also be a way to do this with software. but the two layers are superimposed in one image,
which could cause a problem.
Last edited:
Some software packages such as Sprint but doubtless a few others, allow importing a graphic image (BMP gif JPG) and placing it on its own unconnected layer, precisely for this use, you "tape" pads and tracks over it by hand.
End result is not a formal PCB file, as in no Gerbers, drill guides, etc. so you can not send those to China but black on white artwork , one per layer, is perfect for silkscreening, laser toner transfer or photosensitive boards at home.
In fact, if using a CAD package output, it might guide a CNC engraver to make "direct" milled PCBs.
Or since it is not a standard PCB file but "a drawing" you may also use Corel Draw or similar.
Again, it is "doable", only it takes extra time.
End result is not a formal PCB file, as in no Gerbers, drill guides, etc. so you can not send those to China but black on white artwork , one per layer, is perfect for silkscreening, laser toner transfer or photosensitive boards at home.
In fact, if using a CAD package output, it might guide a CNC engraver to make "direct" milled PCBs.
Or since it is not a standard PCB file but "a drawing" you may also use Corel Draw or similar.
Again, it is "doable", only it takes extra time.