ChromaTalk Archives: October 2010
- (no subject) (3 messages)
- Re: Rhodes Chroma on German Ebay
- Another Chroma recording! (8)
- CPS installed but with two malfunctioning keys :´( (8)
- Looking for a Rhodes Chroma (38)
- ARP Odyssey MIDI mod (12)
- Learn From My Mistakes (10)
- CC+ Set Split-39 (Scratch Patch) Quirk
- Motherboard woes-an update
- Chroma for sale in San Francisco Bay Area (8)
- Re: ChromaTalk Digest, Vol 19, Issue 32 (6)
- question on envelope min-max timing (2)
(no subject)
There were some problems with the list throughout September. I think they are now sorted out.
Chris Borman [21030194+] · Fri, 01 Oct 2010 11:18:03 -0400
Test?
Luca Sasdelli [21010226] · Fri, 01 Oct 2010 17:23:09 +0200
Lars Johansson [21030632] · Fri, 1 Oct 2010 19:49:34 +0200
Hahaha.
Re: Rhodes Chroma on German Ebay
Go to first message in thread, September 2010
Chris Ryan [21030691] · Sun, 10 Oct 2010 10:39:26 -0700
Sold for €2.268,00. "Fully functional;" included an EES MIDI interface.
Picture from the auction:
Another Chroma recording!
Chris Borman [21030194+] · Tue, 12 Oct 2010 21:02:37 -0400
Was trying to figure what keyboard could you possibly put a T8 on?!? The T8 is facing the audience. Then I searched for and found:
The August 1984 issue of DownBeat described Zawinul's keyboard arsenal at the time of Domino Theory. Zawinul's stage setup included seven keyboards: an Oberheim 8 Voice, an ARP Quadra, an E-Mu Emulator, a Rhodes Chroma, a Sequential Circuits Prophet 5, a Korg Vocoder with auxiliary keyboard, and a Prophet T-8. The T-8 was Zawinul's newest instrument, an eight-voice synthesizer with a touch-sensitive keyboard. "I have as much control as you can have," Zawinul said of the T-8. "It's velocity- and touch-sensitive so when you touch down, you can get your own vibrato; you can preprogram your vibrato and speed." In addition, Zawinul used a Linn LM-1 drum machine, a Sequential Circuits Polysequencer, and various harmonizers and digital delay units. [DB84]
WooHoo! - Zawinul solos on the Chroma right at 2:12. You can hear it unmistakably sequenced and solo'd on starting around 6:00 in Birdland.
Chris Smalt [21010280+] · Wed, 13 Oct 2010 16:59:42 +0200
Yeah, I saw that show (in Holland). It's where I first heard Birdland, and this is why I've never been able to get used to the original (non-swing) version. My decision to get my first Chroma (1985) was largely based on what Zawinul said about it in a Keyboard Magazine interview around that time.
Marais · Wed, 13 Oct 2010 11:42:04 -0400
Didnt' Zawinul also find a way through modulation or something to invert the keyboard on the Chroma ?
Jesper Ödemark [21010135] · Wed, 13 Oct 2010 17:34:06 +0200
It can easily be done. I accidentally did so while programming in the beginning. Weird indeed! :)
Dave Manley [21030547] · Wed, 13 Oct 2010 12:46:11 -0700
Zawinul was famous for having two 2600's with one keyboard inverted. I haven't heard that about the Chroma though.
John Leimseider [21030434++] · Wed, 13 Oct 2010 13:48:14 -0600
I worked on a couple of Chroma Expanders for Joe about 10 years ago. There were definitely a few "backwards" programs… I have the programs somewhere… There was also a program with a split with a symmetrical program, going up in both directions from the middle. To me they were interesting rather than usable for what I was doing musically…
Jeff Bova [21030407++] · Wed, 13 Oct 2010 12:57:58 -0700
It's been a while since I've had an instrument in front of me but if I recall , use the keyboard as a modulation source as applied to the oscillators using a negative setting. Use one of the modulation sources with the deepest available depth such as OSC Mod 3 will invert the keyboard pitch.
Chris Smalt [21010280+] · Wed, 13 Oct 2010 22:37:16 +0200
And less intense modulation of you want to go microtonal. I used this quite a bit for effect sounds (claps, thunder, a can of spray paint), where you want every sound to be a tiny bit different.
CPS installed but with two malfunctioning keys :´(
Jesper Ödemark [21010135] · Fri, 15 Oct 2010 15:26:21 +0200
Hi fellow chroma addicts,
21010135 underwent surgery today and is naked on my living room "table" (I write "table" 'cause I use the Chroma case as table even when not in synth surgery mode). Left to do is to adjust sensitivity and screw connections. I've encountered one problem though and need help to figure out if it's hardware problem or me... I get weird response on two keys (G and G# (key 47/48) just above middle C).
I haven't adjusted sensitivity or screw fittings yet, but all other keys respond well to the aftertouch except these two. I've reattached the connectors and also tried reprogramming to velocity response over the filter to check that the Chroma itself is OK (which it seems to be). What happens is that key 47 and 48 cannot get the aftertouch to respond. The filter is closed and sound very muffled if played normally. If I hit the keys really hard and quick I get a fully opened filter, but there is no way to open it halfway not to control it with the aftertouch.
Have I missed something crucial here or is it my usual luck, that parts of the CPS is broken? :(
Luca Sasdelli [21010226] · Fri, 15 Oct 2010 16:34:33 +0200
Hi jesper,
only two adjacent keys sounds like a CPS motherboard fault. Just not to leave anything left, I suggest to try in adjust the wooden bar using the two big vertical screws near the center of bar. Anyway, try to disassemble the wooden bar again and check its profile for any linearily issue: it must appear very linear.
Good luck!
Chris Borman [21030194+] · Sat, 16 Oct 2010 11:09:54 -0400
Good pressure operation on all other keys would indicate the sensor/damper bar positioning is correct. Check the position of the key weight and verify proper contact. Just compare with good keys. Other than that it is probably a faulty middle right FSR or right sensor board. Maybe an circuit trace open or short or the FSR is somehow goobered. I would expect a MUX board failure to likely take out sixteen keys at a time, not just two.
With power OFF, measure ohms between sensors 47/48 and pins 17/16 respectively of IC3 (4067, 3rd from the potentiometer) and the +5VA line (SV5 pin 4 or any of the two center pins of the Sensor connectors) - See .pdf attachment. Should be open with no pressure, approx 30K-40K ohms with full pressure. Just manually press the key while measuring. Next step would be to remove the CPS/Damper assembly and check again manually pressing the sensor. Just place tick marks at those key/sensor positions. (See Pic)
Start with these two suggestions. If you have proper contact and your getting a good reading, then I will send you a new MUX. If not that simple, then we'll take a more in-depth look at the actual 47/48 sensor.
Chris Borman [21030194+] · Sat, 16 Oct 2010 11:46:57 -0400
Oops! I circled pins 17/18. should be 16/17...
Jesper Ödemark [21010135] · Sat, 16 Oct 2010 18:12:10 +0200
Thanks Chris,
I'll follow the doctors advice asap. Will get back after that. Apart from this I can only send praise... Amazing to fiddle around with Vangelisesque pads when you have aftertouch at your fingertips. :D
Jesper Ödemark [21010135] · Sun, 17 Oct 2010 16:18:24 +0200
Hi list and Chris B in particular,
Good pressure operation on all other keys would indicate the sensor/damper bar positioning is correct. Check the position of the key weight and verify proper contact. Just compare with good keys. Other than that it is probably a faulty middle right FSR or right sensor board. Maybe an circuit trace open or short or the FSR is somehow goobered. I would expect a MUX board failure to likely take out sixteen keys at a time, not just two.
Everything OK this far...
With power OFF, measure ohms between sensors 47/48 and pins 17/16 respectively of IC3 (4067, 3rd from the potentiometer)
Good readings. Double checked values with other connectors based on the schematics. I measured as close to the sensors as possible (i e solder side -> IC legs).
and the +5VA line (SV5 pin 4 or any of the two center pins of the Sensor connectors) - See .pdf attachment. Should be open with no pressure, approx 30K-40K ohms with full pressure. Just manually press the key while measuring.Next step would be to remove the CPS/Damper assembly and check again manually pressing the sensor. Just place tick marks at those key/sensor positions. (See Pic)
Great on every key except 47 & 48. My digital volt meter was messy to read so I switched to my analogue (I knew this would make itself really useful one day!) and every keys measured displays a value 'round 38. Key 48 can be pushed to 6 or 7 KOhms. Key 47 up to 2 KOhms. This with full (i e aching finger) pressure.
Start with these two suggestions. If you have proper contact and your getting a good reading, then I will send you a new MUX. If not that simple, then we'll take a more in-depth look at the actual 47/48 sensor.
Does this mean it's the sensor itself then?
Chris Borman [21030194+] · Mon, 18 Oct 2010 19:40:17 -0400
Hi Jesper,
Zero OHMS without any pressure? Any readings less than 10K is probably a shorted PCB. The right sensor is a single PCB and two FSR arrays. 47/48 are the last two FSR's of the array. Note both the LEFT and RIGHT sensor PCB's are identical, one is just flipped over. Both the Top and Bottom FSR circuits are connected through the VIA and mux header, so a short can be on either side. Zero OHMS with no pressure indicate the circuit is fine, most likely some conductive particle stuck to the FSR
Just to be sure, isolate the MUX PCB from the FSR Sensor Array by carefully unpluging it, then again ohm out 47/48 to +5v.
A replacement MUX board would be the least expensive to send you. If it is truly the FSR sensor, I think it would be best to just replace the faulty Right sensor. That would require you to take a sharp xacto knife to cut through the felt right where the Left & Right FSR Sensors meet. Then carefully pry the right (faulty) sensor off the wood spacer. This leaves the remaining Left Sensor and complete wood spacer attached to your Damper bar.
I can send a replacement Right sensor complete with FELT. You would just need to position and reglue it to the wood spacer. I would use the MUX as the guide - On a flat surface, plug the MUX back into the Left Sensor/Spacer/Damper assembly. Lightly coat the right half of the wood spacer with non-conductive multipurpose adhesive (I use 3M Super 77 Spray) then carefully plug in the replacement sensor while aligning it with the wood spacer and press it all down until set.
Chris Borman [21030194+] · Mon, 18 Oct 2010 20:11:40 -0400
Actually, Zero ohms no pressure, 30k-40K ohms or full key pressure, but likely a lot lower reading using your finger because the actuation surface is much larger than the thin edge of the key weight. Besides damping, the felt layer actually increases the effective pressure area.
Looking for a Rhodes Chroma
Odysséas Tsakas-Grigoriadis [21010242] · Thu, 21 Oct 2010 10:34:31 +0000
Hello list,
I am relatively new to this mailling list, but a very enthusiastic future owner of Rhodes Chroma.
First, I would like to say a big thanks to Chris for creating and maintaining this site, a real work of love, stuffed with the best informations anyone can get for the specific synth! Also, I would like to tell everyone how useful they have been, by asking and answering questions about the Chroma. They've helped me a lot in the learning process!
What I would like to ask, is, if anyone has a Chroma for sale, or knows someone that have a Chroma for sale, I would really appreciate if they could contact me. I am looking for a Chroma in very good confition, if possible with the CC+ upgrade and new PSU. Aftertouch would be a dream! The price I am willing to pay is a max. of 2500euros, which will depend of course on the condition and upgrades present on the Chroma. I am located in Europe, Greece.
I wish to everyone a plaisant winter!
Jesper Ödemark [21010135] · Thu, 21 Oct 2010 14:14:08 +0200
Odysséas, it almost sounds like a polyphonic version of the Odyssey... i e, almost a Chroma! :D
We'll keep our eyes opened.
Patrik Gudmundsäter [21010240] · Thu, 21 Oct 2010 18:28:25 +0200
I have one i might sell, but not for 2.500 Euros. Just the costs to repair it were over 2.200 Euros.
Sandro Sfregola [21010294] · Thu, 21 Oct 2010 22:26:39 +0200
Your budget is low for even a non upgraded (no CC+, no SPSU), well working Chroma. I think that its current value in Europe is near 4000 euro. Another option would be to buy a broken one, then restoring it but remember that this can be very expensive.
Only my 10c.
Paul DeRocco [21030230] · Thu, 21 Oct 2010 14:20:09 -0700
...unless, that is, you're a good technician yourself, and can capitalize your own labor. The parts cost of repairing a Chroma is often modest, unless you're unlucky enough to need to buy some rare part, like a 7541 DAC, a TIL393 8-digit display, or a CEM3350 or 3360 chip.
Chris Ryan [21030691] · Thu, 21 Oct 2010 18:23:33 -0700
On 2010-10-21, at 1:26 PM, Sandro wrote:
Your budget is low for even a non upgraded (no CC+, no SPSU), well working Chroma. I think that its current value in Europe is near 4000 euro.
Check the price history for recent values.
Doug Terrebonne [21030114] · Thu, 21 Oct 2010 22:57:33 -0700
I have one i might sell,but not for 2.500Euros. Just the costs to repair it where over 2.200 Euros.
Jeez, who did you have do the repairs? What all was done?
Odysséas Tsakas-Grigoriadis [21010242] · Fri, 22 Oct 2010 07:00:56 +0000
Hi everyone and thanks for the replies.
The amount I said I am willing to give was based on the site's price list, and on anything I saw on the internet for six months now.
What I saw was that a Chroma could sell for 1800e until 2900 max. Never believed that the Chromas could get this high in Europe (well, yes if it was sold by RLmusic).
Again, maybe I'm wrong but, this is the price I thought was ok.
Jesper Ödemark [21010135] · Fri, 22 Oct 2010 09:45:22 +0200
Check the price history for recent values.
*ouch!*
I've totally missed Lars' story of the Gullspång flea market Chroma. 100 SEK, that equals a bloody flick ticket these days. Back then maybe two... :-o
I need to visit flea markets more frequently... ;)
Jesper Ödemark [21010135] · Fri, 22 Oct 2010 09:48:41 +0200
Jeez, who did you have do the repairs? What all was done?
They run a company. If you charge the price/hour tech style it easily get's expensive.
If you ask a pro to fit the CC+ or CPS or new PSU etc I bet you'll pay 200-300 USD at least.
Peter Forrest [21010096] · Fri, 22 Oct 2010 09:49:31 +0100
Welcome to probably the best single-product (ok dual product) website around, Odysséas! I don't think it's out of the question to find a Chroma for the sort of money you were suggesting, but you may have to be fairly quick or lucky. It's worth bearing in mind that many of those instruments on the price history list were not 100% working. And I'm not sure that anyone who has gone to the trouble of having all the latest available improvements fitted in their machine will let it go for that sort of price. But an unimproved Chroma in decent working and cosmetic condition should be around somewhere in Europe for that money - or in the USA for two-thirds that, which, after import costs to Greece, probably works out about the same.
Luca Sasdelli [21010226] · Fri, 22 Oct 2010 11:05:18 +0200
I agree with Peter. Indeed, the instrument is old, so many items could be faulty or simply out of spec, leaving a partially working (or easy to fail) instrument; on the other hand, I believe all new mods are quite easy to implement, so they can be evaluated at their native cost and fitted by the owner.
The really expensive part of the whole stuff is its restoration: I've just terminated a Chroma restore that, even in spare time, took my work from last april to the past month; not to mention the CEM chips purchase.
BTW: Heinz, any news about the C2? :) Would it use the CEM3396 or which else?
Jesper Ödemark [21010135] · Fri, 22 Oct 2010 11:11:02 +0200
I agree. With a bit of luck a european Chroma could end around 20000 euros and then you have to add whichever improvements you want yourself. The Chroma still has a bit shaky reputation so keep your fingers crossed.
And since Peter is so modest, don't forget to check the vemia auctions next month. There has been a few Chromas there over the years.
Peter Forrest [21010096] · Fri, 22 Oct 2010 11:10:52 +0100
Thanks Jesper!
Odysséas Tsakas-Grigoriadis [21010242] · Fri, 22 Oct 2010 11:13:15 +0000
Hello Peter, and thanks for your words. I'm already checking VEMIA, with the hope there will be a Chroma this time.
Patrik Gudmundsäter [21010240] · Fri, 22 Oct 2010 13:34:12 +0200
1.Bying a Chroma.To.Sandro.
Yes,you are 100% Right Sir! A broken one, if you find one is realisticly about 2.000 Euros or more. I can just see to all the hours spent to repair mine here and make it in 100% working order.
I haven't put together all Invoices from my tech yet, but it was over 2.000 Euros. He has fixed all the 8 voice cards, etc. MIDI works, SPSU is installed properly etc.
I think, it's better to buy one that works. It's not so easy to find someone capable to work on them anyhow. Not in Sweden/or anywhere else!
If you are a trained tech, then you might have a different situation, but you need to know how to handle a Oscilloscope, etc. Also the Rhodes Supersite was a great help to repair it with all the info. Thanks again for that!
Jesper Ödemark [21010135] · Fri, 22 Oct 2010 13:38:44 +0200
Patrik Gudmundsäter skrev 2010-10-22 13:34:
I think, it's better to buy one that works. It's not so easy to find someone capable to work on them anyhow. Not in Sweden/or anywhere else!
Just curious... who did the work on your unit? I have my "personal doctor" just kilometers away (in Lund) but am still interested to hear of others. Pro tech or skilled hobby tech?
Patrik Gudmundsäter [21010240] · Fri, 22 Oct 2010 13:47:32 +0200
Well,if you are not a tech.Buy a restored one.Not an object!It's a nightmare. Or keep on dreaming of that flea market.
Jesper Ödemark [21010135] · Fri, 22 Oct 2010 14:05:53 +0200
Patrik Gudmundsäter skrev 2010-10-22 13:47:
Well,if you are not a tech.Buy a restored one.Not an object!It's a nightmare. Or keep on dreaming of that flea market.
I never meant for you to get irritated if that is what you got. I was honestly interested in where your unit was served and I also remembered that you fixed one up to sell. Therefor I see you mainly as a seller and not a user.
I bought my Chroma on Ebay Germany. It was fully functional and I've replaced PSU, added CC+ and most recently CPS (though I await spare part from Chris). None of these additions are tech extravaganza.
Total cost including shipping etc is in the region of 1600 euros. Worth every penny and yes, one day something will break that I cannot fix myself, but this is true for all the Chromas (and other gear) out there (that they'll break, not that everyone will need an exterior tech to service them).
So, offer your at 4500 (or was it 4000) or simply accept the fact that there still are bargains to be had for those willing to wait. I think Chris has done a great job compiling the list of recent prices and it's a good guideline. Not for the "market value" but as a taste of possible prices out there. Both regarding bottom and top end of the list.
Jesper Ödemark [21010135] · Fri, 22 Oct 2010 14:06:55 +0200
Patrik Gudmundsäter skrev 2010-10-22 13:55:
Well,he is a Pro tech.He was in Charge of Luthmans tech department in the past.And Has repaierd instruments since the seventies., and has had his own shop,but now mostly work for me for the last 10 years.
He is specialized in reparing Organs,Leslies,Synthesizers, and other Music equippement.Malte is his name.
Thanks! :D
Heinz Weierhorst [21010276] · Fri, 22 Oct 2010 14:49:37 +0200
Hi Luca.
It's not me working on the C2. I just tried to make a replacement for the obsolete CEM3350 filter ship. It can be done with LM3700 Otas which works in simulation and in practise - but - you need a PNP array for control. That's where the trouble starts. Not only Analog Devices ceased production of quad PNP arrays and the only remaining producer is THAT Corporation, all controls i.e. freqency and resonance are inverted. If someone is interested I can show the schematic - may be there are better solutions. But I like the design of the CEM 3350 - it's so unique and does - in my opinion - a lot of the Chromas sound.
Luca Sasdelli [21010226] · Fri, 22 Oct 2010 15:34:41 +0200
Hi Heinz,
thanks for the details. I thought it was a sort of CEM3396-based redesign.
The question was just to understand the status of the VCF matter; the Chroma I've just restored had a failed 3350 and - luckily - a destroyed DVB had a working one to re-utilize, but in case there should be another one broken, it would be a real nightmare; therefore I was looking to other solutions to fix such as a failure. By hearing the Dave Smith Prophet '08 sound, I guess the 3396 could be a good choice, but it should need a complete redesign of DVB (and CMB!), probably by keeping the original charge-pump VCO combined with the "new" monolithic chip. Such as an hypotetic redesign could include a finer resonance control, but it's still a generic (and funny) idea.
Daniel Rickenbach [21010172] · Fri, 22 Oct 2010 15:49:35 +0200
Hi Heinz
I have found some Transistor Arrays PNP also made by intersil (google). I'm interested in the schematic. I'm not an electronic engineer, but it's only for interest. How do you "catched" the "inside" of the CEM3350, I found only block diagrams about this Chip?
Heinz Weierhorst [21010276] · Fri, 22 Oct 2010 16:09:00 +0200
Hi Daniel.
I know that array from Intersil, may be HFA 3128 or so. The trouble is it's only for voltages around 8V max - but the Chroma has 12V. Schematic will come soon.
Patrik Gudmundsäter [21010240] · Fri, 22 Oct 2010 17:10:39 +0200
No,some of it are not. But if you have to pay for a tech, like I did and make the thing work, it's not free. Don't know what the rates are in South Sweden, but here normally arround 600SEK for each hour. But still, now it works fine.
Jesper Ödemark [21010135] · Fri, 22 Oct 2010 17:30:12 +0200
Which... in the end, is all that matters. :)
Johnny Vintage [21010244] · Fri, 22 Oct 2010 18:03:22 +0200
I just (last month) sold 2 Chroma's.....first one: fully serviced with CC+, new PSU both org. manuals, org. dual pedals, org flightcase in almost mint condition € 3000,-
Second one: fully serviced with JL Cooper midi and new PSU in very good condition € 2650,-
Few weeks ago on ebay: [item #280567142916]
So they are stil available at reasonable prices, but i'm very sure they'll get more and more expensive in the future because they are awesome.
Odysséas Tsakas-Grigoriadis [21010242] · Fri, 22 Oct 2010 16:09:08 +0000
Come on Johnny, don't you have a spare one for me? :-)
Anyway, I have a friend who knows his way around with electronics (made some repairs on a faulty CS 80, which now works), who could help me "upgrade" my future Chroma. But one in full condition would of course be better.
Patrik Gudmundsäter [21010240] · Fri, 22 Oct 2010 18:26:13 +0200
They are, and you won't normally find one from your local Music store. They are not any New ones from Rhodes either :)
Few made, few left, and we try to keep them alive. Due to Internet, youtube etc. has prices on som Vintage gear gone up quite a lot in later years. Just look at Mini Moog, Wurl A200, Clavinets, Prophet 1 and 5, also 600. Yamaha CS80, etc but also some lesser models from Roland, SH1000, 2000, etc. Moog, Oberheim, etc even Farfisa, Elka, Siel, Acetone, Old drummachies etc. Also old Hammond organs. Particullary B3, C3, A100, RT3, D100, M3, M100. And Leslies like 122, 147, 145, 142, but also 770 series is more interesting.
These are some things Musicians are very interested in, but you normally don't see so often in the Music stores. I think that the interest for this kind of Vintage gear will just continue to increase. But it's a lot of work to keep them alive. Usually this sector is forgotten by the more finecultural people, but still its a great Music Cultural work we do every day!
Paul DeRocco [21030230] · Fri, 22 Oct 2010 10:20:33 -0700
From: HW
It's not me working on the C2. I just tried to make a replacement for the obsolete CEM3350 filter ship. It can be done with LM3700 Otas which works in simulation and in practise - but - you need a PNP array for control. That's where the trouble starts. Not only Analog Devices ceased production of quad PNP arrays and the only remaining producer is THAT Corporation, all controls i.e. freqency and resonance are inverted. If someone is interested I can show the schematic - may be there are better solutions. But I like the design of the CEM 3350 - it's so unique and does - in my opinion - a lot of the Chromas sound.
You mean the LM3900, don't you? That's how ARP made their VCFs. And they used ordinary 2N5087 or 2N3906 transistors clipped together for thermal contact, binned and selected for reasonably low offset. Worked pretty well, but required a CV feedthrough trim, which was never perfect. The Curtis chip worked better. I wouldn't try to cobble together an alternative.
Paul DeRocco [21030230] · Fri, 22 Oct 2010 10:29:56 -0700
From: Luca Sasdelli
The question was just to understand the status of the VCF matter; the Chroma I've just restored had a failed 3350 and - luckily - a destroyed DVB had a working one to re-utilize, but in case there should be another one broken, it would be a real nightmare; therefore I was looking to other solutions to fix such as a failure.
Why is it a nightmare? How much do CEM3350 chips fetch these days? I expect they're expensive, but not as expensive as the time to design and build an adapter board to make something else work.
Heinz Weierhorst [21010276] · Fri, 22 Oct 2010 20:44:08 +0200
Hi Paul.
You're right about the price. But in Europe the CEMs are very hard to find. You can easier get fresh strawberries harvested at the southpole than getting that integrated circuits. On the other hand it makes much fun to work on such a replacement even when it takes much time and isn't really finished that time. When working on an old product like the Chroma is and one can do much alone the spended time does not really matter. But o.k. time is money.
Chris Borman [21030194+] · Fri, 22 Oct 2010 14:51:54 -0400
If I had free money to live on, I would spend all my time fishing, hunting, goofing with my boat and comming up with more Chroma h/w and of course working out my Digital Percussion Instrument. I don't have any free (or easy) money, so I spend my free time doing those things that bring me peace... Just saying that cash ain't the only way to get paid!
Chris Borman [21030194+] · Fri, 22 Oct 2010 15:37:21 -0400
And I forgot to add, listening to music. My all time favorite activity especially when accompanied by a visual augment such as a LASER show -Audio Visual Imagineering all the way!
Luca Sasdelli [21010226] · Fri, 22 Oct 2010 22:06:16 +0200
Il 22/10/2010 20:44, HW ha scritto:
You're right about the price. But in Europe the CEMs are very hard to find. You can easier get fresh strawberries harvested at the southpole than getting that integrated circuits. On the other hand it makes much fun to work on such a replacement even when it takes much time and isn't really finished that time. When working on an old product like the Chroma is and one can do much alone the spended time does not really matter. But o.k. time is money.
Confirm. Sometimes CEM3360s are available, but the 3350s are disappeared since long time. I've just bought a couple of 3360s from Holland for 60 euros each: this seems to be the current price of double VCA, but the VCF is at present nearly impossible to find out.
Dave Manley [21030547] · Fri, 22 Oct 2010 13:10:41 -0700
From: Paul D. DeRocco
You mean the LM3900, don't you?
Looks like a typo - he means LM13700.
Paul DeRocco [21030230] · Fri, 22 Oct 2010 13:30:29 -0700
Looks like a typo - he means LM13700.
Oh, yeah, I remember that part.
The LM3900 had the same sort of bias current input: a diode to the minus rail. ARP used a single-output expo converter, and simply used resistors to split the current equally, chosen based on the max current needed. Typically, you want to run expo converters over something like a 300nA to 300uA range (for 16Hz to 16KHz), so 33K resistors would work. However, at the low current end, where you only have 10mV across the resistors instead of 10V, the difference between the bias input diode drops starts to skew the current splitting, and affect the Q of the circuit.
It's interesting to study some of the old module schematics, which can be found here: ARPtech - Submodules
You'd be surprised at what we got away with back at ARP, without resorting to matched transistor arrays, etc.
Heinz Weierhorst [21010276] · Sat, 23 Oct 2010 15:21:58 +0200
Looks like a typo - he means LM13700.
Hi all.
Yes, it was a typo. It should read LM13700. That ARP design with the LM3900 uses the NPN current mirror build in such a so called Norton Amplifier with two external PNP transistors to hook up a transconductance cell. The SSM 2040 works very close but has a PNP current mirror and a NPN differential pair and a darlington buffer. Some people around the internet say the SSM 2040 is the best sounding filter ever. I never listen to one. I only know the SSM 2044 which is a tricky design to overcome MOOGs patent for the ladder-filter.
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ARP Odyssey MIDI mod
Luca Sasdelli [21010226] · Sat, 23 Oct 2010 22:05:14 +0200
Hi all,
should anybody be interested in MIDI-ing an ARP Odyssey, I've just modded my one and the result is really good, so if needed I can post the relevant infos here.
P.S.: MIDI IN only; cost below 80 euros including special tool
Peter Forrest [21010096] · Sat, 23 Oct 2010 21:21:05 +0100
Hi Luca,
Congratulations - sounds like excellent value! It could be good info for the Analogue Heaven and Synth-DIY forums.
Chris Borman [21030194+] · Sat, 23 Oct 2010 16:33:29 -0400
What H/W did you use?
Johnny Vintage [21010244] · Sat, 23 Oct 2010 22:43:08 +0200
Hi
Only note info or controllers also ?
Luca Sasdelli [21010226] · Sat, 23 Oct 2010 22:49:01 +0200
Hi Chris,
I've installed MIDImplant
The polish guy builds some interesting modules; the one I've bought came together with an individual graph of relevant CV/oct response, with very tight tolerances. It's fully programmable via an embedded setup contact, and all set-up data are fed via the external MIDI keyboard using keys and expression controls. Its size is so small that it is soldered directly on DIN socket pins.
The interface with Odyssey hardware is very simple, because of the common 1V/oct standard and gate/trigger pulses are directly compatible; my one is a 2811 (Odyssey II): in case of the 2810 series it should be checked with that special gate/trigger circuitry (3 contacts per key instead of 2). I've chosen to use a switch to select either inner keyboard or MIDI input.
The only needed tool is the special punch to cut round holes for the DIN plug (16mm); here 25 euros, but in USA is found at around 12US$.
Time to complete about 3hrs, included fully re-tuning of the synth.
Luca Sasdelli [21010226] · Sat, 23 Oct 2010 22:55:15 +0200
Hi John,
the module is fully programmable: I was really impressed in reading all embedded features and set-up capabilities.
The module has two CVs and two Gate outputs, all of them programmable; by default, CV1 is key value and CV2 is key velocity, but they can be mapped to almost any MIDI controller.
An interesting improvement could be to use CV2 (velocity) to drive a VCA (LMH6502) inserted between ADSR and VCF, to control EG expression over VCF with key dynamics. This would require a mod in the ADSR amount slider and relevant circuitry.
David Gowin [21030611] · Mon, 25 Oct 2010 09:04:44 -0400
Sounds quite interesting, I have an Odyssey II with the updated kit for CV IN/OUT, etc
Luca Sasdelli [21010226] · Mon, 25 Oct 2010 21:27:29 +0200
Hi David,
which CV IN/OUT kit are mentioning? The 2811 already had CV+gate+trigger IN/OUT connections; perhaps another mod?
About the MIDI interface I've chosen, as reported on other posts is an excellent piece of hardware capable to convert MIDI data into CV and Gate, on two separated lines: it is therefore possible to use them to play the Odyssey in bi-phonic mode as per its own design, or use the CV2 (defaulted to velocity data) to modulate some other synth parameters.
Jesper Ödemark [21010135] · Tue, 26 Oct 2010 09:47:39 +0200
For the mk1's maybe? My whiteface has a Kenton socket kit. cv/gate/trig/filter cv. Works great.
Luca Sasdelli [21010226] · Tue, 26 Oct 2010 10:42:00 +0200
Hi Jesper,
perhaps the confusion is about release codes. David said he has an Odyssey II, but it seems a 2800 i.e. Odyssey I (no factory installed interface jacks, service manual page 1.3).
The Odyssey II is 2810-2813; series III is 2820-2823.
Jesper Ödemark [21010135] · Tue, 26 Oct 2010 10:48:50 +0200
Yes, there are "blackfaces" without cv/gate jacks too. Annoying move by ARP... Easier with a whiteface. Mine is from the summer of '72. Serial 28079 so no original jacks in sight. :)
More On-topic. Regarding my CPS-problem. Spare part to arrive in the (hopefully near) future. Sad to see the girl stripped like that on her stand...
David Gowin [21030611] · Tue, 26 Oct 2010 09:32:21 -0400
Sorry, but mine was an Ody II (Gold Face, no PPC, no CV/Gate/Trigger initially), but I purchased a mod kit from old ARP Service stock and had it installed
Learn From My Mistakes
Matrix [21030220] · Sat, 23 Oct 2010 17:57:57 -0700
My Chroma is on the fritz. I'm talking with Dave [21030085++] offline on picking up a CC+ upgrade and working on seeing if I can get it going beforehand. When the problems started, it would turn on and everything would be fine for about 10 seconds. Then the display would go out, nothing would play and the leds would just flickr. Now the LEDs just flickr and nothing plays when turning it on. I'm in the process of replacing the original baby blue capacitor. The holder was on tight and I couldn't quite get to the clamp screw to loosen it, so I figured I'd unscrew the holder from the board and then get at it. I had no idea it was attached to nuts underneath the board. :) I got it off but now have no way of getting it back on. I just thought I'd send this to the list as a warning/tip to others. Do not remove or even loosen the holder from the circuit board. On a side note, I was going to try and remove the whole board so I could screw the holder back in place. I started unscrewing another component and then immediately thought I should check if it was also attached to a nut. Sure enough, it was. Fortunately I tested this before unscrewing it too much. It's too bad the Chroma doesn't have a "window/plate" underneath that you can remove to get to the nuts underneath.
Anyway, I plan to use earplugs in place of the screws to fasten the capacitor holder back in place. I figure I can squeeze them through the hole and they will expand and hold it snugly in place. Does anyone know if there is a reason why this is not a good alternative? BTW, considering the weight of the Chroma, it pretty much has a permanent place in the studio and I have no plans on ever selling it, so I'm thinking this solution will be OK considering.
Dave Bradley [16330135] · Sat, 23 Oct 2010 21:46:17 -0500
What? Earplugs?
Matrix [21030220] · Sat, 23 Oct 2010 20:28:16 -0700
Hah! Yes! I was trying to think what I could use in place of screws. I can't hold the nuts in place to screw the existing screws back in place and I don't want to damage the circuit boards with larger screws. I originally thought of using rubber stoppers but wondered how I'd find ones the right size. I then thought of ear plugs. With ear plugs you squish them narrow, place them in your ear, and then they expand in place. I think they'd work great. Honestly, I might just go with the existing screws sitting there, but it would stink if I forgot years from now, moved the Chroma and they got loose.
Dave Bradley [16330135] · Sat, 23 Oct 2010 23:13:53 -0500
I guess I don't see the difficulty in putting it back together correctly. You just need to remove the circuit board in order to remount the capacitor, right?
Luca Sasdelli [21010226] · Sun, 24 Oct 2010 09:49:39 +0200
I agree with Dave.
It's enough to remove the back metal panel from base and the four screws fixing the PSU PCB to bottom. Of course, pay attention to wiring: better to fasten them with tie-wraps or by winding them in silicone spirals to keep'em safe from unwanted pulls.
The low voltage connectors should be disconnected to allow better access to bottom of PCB: clearly mark them with a felt pen for smooth surfaces, and/or write down the colour combinations before detaching from plugs.
Matrix [21030220] · Sun, 24 Oct 2010 09:50:57 -0700
Excellent. I'll take another look before I go with ear plugs. :) Plastic screws might be an option as well. I guess it will depend on risk vs. time vs. what works. Primarily, I cherish my Chroma and don't want to risk making it worse. I'll never sell it so I'm not worried about "passing" it on to anyone else.
Jesper Ödemark [21010135] · Sun, 24 Oct 2010 19:14:07 +0200
A better option is to change the entire PSU. I've kept the blue cap' as a souvenir and the old transformer is also on display on a shelf. :D
Matrix [21030220] · Sun, 24 Oct 2010 12:55:25 -0700
The holder is re-attached. Unhooking the board from the underside wasn't too bad.
Matrix [21030220] · Wed, 27 Oct 2010 19:32:07 -0700
And my Chroma has risen from the dead. The new cap did the job and I was able to program factory patch Brass I on it. Thanks goes to David Clarke for some help offline. Next stop is the CC+ upgrade.
Jesper Ödemark [21010135] · Thu, 28 Oct 2010 13:35:31 +0200
Yezzzzz - congrat's! :D
CC+ Set Split-39 (Scratch Patch) Quirk
David Clarke [21030085++] · Sat, 23 Oct 2010 22:27:03 -0400
While performing unrelated testing, it was noticed that creating a Scratch Patch by using the Set Split-39 shortcut of the CC+ will inadvertently clear the 'link' data for Program 1.
An update to this behaviour will be considered in a future CC+ firmware release.
Best regards,
David Clarke
(Note: This behaviour has been present in all CC+ firmware releases to date.)
Motherboard woes-an update
See earlier thread Re: Motherboard woes?-DIAGNOSTIC UPDATE, July 2010
RJ Krohn [21030455] · Mon, 25 Oct 2010 11:53:39 -0700
hi all, so i wanted to give an update on my progress to revive my chroma. as i believe the problem to lie on the motherboard, here is some more info that may help the few others on the board, as well as a few questions...
as i had socketed every IC on the MB, i took it out and checked the continuity of EVERY solder joint, including all the joints of the ribbons. each looks good, and i detected no bridging on any joints.
what i DID find was a bit of corrosion underneath 2 of the VB harnesses. so i desoldered them, cleaned out the areas, and soldered them back in.
upon powering up, i got a SIMILAR problem, but slightly less. the machine would let 1 voice sound, i.e. play as if in unison mode, whether there was 1 or 4 VB's seated. it would play that one voice in tune across the keyboard, which is a first. it would also execute multiple autotunes, i.e. i could consecutively autotune the machine. then, that voice would go silent, and it would fail to enter autotune, but this would be after 1-10 minutes, depending on which time i turned it on/off.
HOWEVER, if i swapped IC's 10 and 11 for 12 and 13, it would NEVER enter autotune. at ALL. while all 4 are 4556 logic ic's, i ran out of TI brand when replacing the MB iIC's, so 2 of those are ON Semi brand(which i have actually had fail on other machines before, but who knows if this is a culprit or not here). no autotune, and none of the voices will sound at all, EVEN after split-31 or split-50.
i ordered ANOTHER set if ic's for the MB today, as its the only shot in the dark i have left, but figured i'd sound this off you guys to see if anyone has any ideas behind this. if this doesnt work, im sending the MB to a tech, and writing off hearing the first chord out of this thing for another ???? weeks/months. thanks for the help, rj
Chroma for sale in San Francisco Bay Area
Thomas Story [21030352] · Thu, 28 Oct 2010 18:57:00 -0700
[craigslist posting #2030739124]
I have no interest in the sale of this machine, just passing the information along...
Chris Ryan [21030691] · Thu, 28 Oct 2010 19:52:26 -0700
I heard from the seller earlier today. This is Chroma 21030114, previously in the registry, but only from the Fender warranty registration list (it was double-registered, perhaps once by someone misreporting a serial number). "All lights lit like a Christmas tree" when he turned it on after pulling it from storage after seven years. It's listed at USD$1800.
Doug Terrebonne [21030114] · Thu, 28 Oct 2010 21:55:10 -0700
Yeah I have been in contact trying to buy it locally. I told him I successfully repaired my previous Chroma. I suspect my chances now are not so good. :(
Johnny Vintage [21010244] · Fri, 29 Oct 2010 08:37:45 +0200
That's a very nice power supply :-)
Luca Sasdelli [21010226] · Fri, 29 Oct 2010 10:40:00 +0200
Il 29/10/2010 04:52, Chris Ryan ha scritto:
I heard from the seller earlier today. This is Chroma 21030114, previously in the registry, but only from the Fender warranty registration list (it was double-registered, perhaps once by someone misreporting a serial number). "All lights lit like a Christmas tree" when he turned it on after pulling it from storage after seven years. It's listed at USD$1800.
Well... in a couple of months it would become useful, but what a price! :)
Patrik Gudmundsäter [21010240] · Fri, 29 Oct 2010 18:06:06 +0200
Not right tactic, if you want to buy it cheap! :) They are expensive to repair for anyone who can't!!
Doug Terrebonne [21030114] · Fri, 29 Oct 2010 16:25:07 -0700
21030114
I just bought Chroma 21030114. :)
So now I have a Chroma again after foolishly parting with my old one I restored for $700 in 2005. Hopefully the repairs on this one won't be too bad. I'll probably put it a new power supply and do the CC+ upgrade.
Matrix [21030220] · Fri, 29 Oct 2010 17:03:52 -0700
Re: 21030114
Congrats! I wouldn't be surprised if it's the original baby blue cap. Mine was displaying the same behavior and the simple cap replacement fixed it. I wasn't ready to justify the cost of a new power supply just yet myself. The cap was just over $30 after tax from Digikey. If you need the part number I went with let me know and I'll dig it up.
Re: ChromaTalk Digest, Vol 19, Issue 32
Patrik Gudmundsäter [21010240] · Sat, 30 Oct 2010 22:16:36 +0200
I wonder why my name is spelled with a questionmark?:) Rather change to "Gudmundsater" It looks pretty silly.
In the digest, Patrik's last name appears as "Gudmunds?ter."
Chris Ryan [21030691] · Sat, 30 Oct 2010 15:17:59 -0700
The mailing list software, or some email server somewhere, is not correctly translating the 'ä' (a umlaut) in your name, and—stupidly—substituting a question mark. It's totally up to you whether you change your name in your email app to use an 'a' without an umlaut in order to bypass this. (I will, however, continue to use an 'ä' HTML entity in your name for the list archives.)
Jesper Ödemark [21010135] · Sun, 31 Oct 2010 10:06:02 +0100
A good way for us nordic citizens is to avoid our odd letters altogether. I don't write my surname that often since it contains those dots too which are always messed up on the net...
The internationally correct way is to use: aa for å, ae for ä and oe for ö. The german ü is translated into ue.
Werner Schöenenberger [21010114] · Sun, 31 Oct 2010 10:39:35 +0100
I am with you (c;
James Coplin [16330036+] · Sun, 31 Oct 2010 09:27:59 -0500
All the email I receive comes through with all your correct accent marks and characters. Is this a client problem and not a server problem?
James R. Coplin – 祽杰明
Patrik Gudmundsäter [21010240] · Sun, 31 Oct 2010 18:18:57 +0100
Well my Correct spelled name is newer in a email adress. Its allways with an a, but my Signature in emails is a different story.
question on envelope min-max timing
Michael Salmon [21030155] · Sun, 31 Oct 2010 14:49:57 -0700
hi all,
i was wondering if anyone knew the following:
- whether attack/decay/release length in time for values are equivalent, eg. 30 "slow" would be the max decay (= .x seconds), does that equal the time of "30" for max release?
- are the values from 0-30 possible to linearly interpolate for attack/decay/release?
- Is there a mode whereby if you shorten the attack (for example, could be another ADR value) that the other values compensate?
In other-words is there a way to have the envelope length fixed and the ADR to auto-normalize when 1 value is changed?
thanks for any feedback on this, I'm trying to be understand the ADR behavior to mimic it to a user-interface in software.
Jesper Ödemark [21010135] · Sun, 31 Oct 2010 23:04:15 +0100
miguel lito skrev 2010-10-31 22:49:
hi all,
i was wondering if anyone knew the following:
- whether attack/decay/release length in time for values are equivalent, eg. 30 "slow" would be the max decay (= .x seconds), does that equal the time of "30" for max release?
I'm quite positive this is _not_ the case. A stretched release is often a lot more useful than a similarily stretched attack or decay.
- are the values from 0-30 possible to linearly interpolate for attack/decay/release?
- Is there a mode whereby if you shorten the attack (for example, could be another ADR value) that the other values compensate?
This sounds very digital to me... But being a non-tech I'm not sure in the Chroma. Most analogue synths have dedicated knobs for the settings as part of the construction. The Chroma is different (as I guess you know). But why implement this function? Seems like a mathematicians wet dream and not anything for a musician. ;)
thanks for any feedback on this, I'm trying to be understand the ADR behavior to mimic it to a user-interface in software.
Can't you "just" measure during trial and error?
Good luck.
Go to next message in thread, November 2010