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ChromaTalk Archives: November 2009

Re: Chroma, Footswitch, Pitch Bend Assembly on eBay

Go to first message in thread, October 2009

Luca Sasdelli [21010226]

Ok, so it was an early SPSU and if I remember there were a couple of mods that needed to be done to fix the sustain pedal polarity or something but I'm guessing there's not much wrong with this unit that a competent person couldn't fix - heck I might buy it off him myself, now that I am in the States.

Hi Mal,

the first batch of SPSU kits needs only one little mod and just on some Chromas: the tantalum capacitor in parallel to the reset button must change from 10uF to 22uF (simply putting a second 10uF in parallel is okay). This solves the sustain pedal issue. I can do the mod for free, but if you can find a local technician doing it locally, you'll save a lot of shipping money; if needed, I can ship a new capacitor for free.

The +12/-12V is not-adjustable and a small difference is allowed: it's compensated by adjusting the trimmer on I/O board for a near-zero reading across the two test points aside the trimmer itself. Should the SPSU being defective, it could be replaced by my supplier within warranty, but the shipping cost is IMHO unsuitable in respect to buying a new one locally.

Polaris membrane

Peter Forrest [21010096]

The non-working Polaris that I won on eBay [302552] arrived across the Atlantic safely, and looking pretty superb too.

It's now up and running, thanks to Keith at Lucid Sounds, except for the fact that the left-hand membrane is shot to pieces.

Does anyone have a suggestion for finding a replacement?

David Gowin [21030611]

If anyone has a solution, I'd be also interested. I have 2 Polaris (Polarii?) and one of them is down because of a membrane issue.

Christian Kleine [21030210]

I can't help but: If anyone has a non-working polaris for sale....i'd be interested (europe, preferably)

Dave Bradley [16330135]

Peter, read this, it might help: Chroma Polaris, RIP [Harmony Central discussion thread]

Chris Borman [21030194+]

Can someone remove the PCB and post a hi-res picture of the switch membrane, specifically the circuit side of the entire pigtail and the other side of the PCB where the connecter is mounted? You won't have much luck soldering to the remaining FPC tail but you can use a compression or ZIF type connector or maybe even glue on a new pigtail.

Peter Forrest [21010096]

Peter, read this, it might help: Chroma Polaris, RIP [Harmony Central discussion thread]

VERY helpful - thanks, Dave!

Robb Witt

The original (prototype) panels were built using silver conductive ink on a mylar substrate, same as the Chroma panels. After the manufacturing of the panels was outsourced they may have made some other changes.

Given the way the panel tails appear to be "dressed", I'd explore getting some conductive ink and a little piece of mylar to build a "bridge".

Peter Forrest [21010096]

Thanks Rob!

Lars Johansson [21030632]

Yeah ! Thanks for all the info guys ( especially the link to HC ).

I have a PPG EVU with the same type of problem.

Now I think it is repairable.

David Clarke [21030085++]

... The non-working Polaris that I won on eBay arrived across the Atlantic safely ... except for the fact that the left-hand membrane is shot to pieces. Does anyone have a suggestion for finding a replacement?

Peter - if it is just the ribbon connection, and if it hasn't already been repaired, you often have enough left to connect on to (either with flying leads, snipping with scissors, or other - as per the other posts).

If the membrane switches are physically damaged though (e.g., membranes worn through), and you don't want to add discrete switches to your panel, I may be able to help. I had a left panel that was too far gone for repair. I bit the bullet and had a left-hand panel membrane replacement made. There was a minimum order, so I ended up with some extras, as attached.

For anyone else that might also be thinking of doing this, I also have the data for the different layers in CorelDraw format (the panel drawing, and the 2 trace layers) if you'd like to use that as a starting point.

Peter Forrest [21010096]

Hi David,

Wow! Those membranes look impressive. Keith at Lucid Sounds is going to have a go at the ribbon connection/s for me, but he said that one looked like it had already had a repair attempt, which doesn't bode too well. Before I gave it to him I noticed that at least in one place the membrane had the tell-tale three-quarter circle ring round it where the switch had worn the membrane.

I wonder if there are firms round the world competent to do that membrane re-creation - and of course how much they would charge, and what the minimum order would be.

I suppose another question is whether replacement membranes' lifespan would be likely to be the same as the originals.

And while I'm thinking out loud... how close did they get on yours to the exact colour and finish of the other membrane? And do they fade with time (so a new left one would look a bit 'wrong' with an old right one...).

Thanks for the advice, and well done on showing it could be done!

Robb Witt

For anyone interested in pursuing this... a few pointers:

The graphics panels should be "back-screened" with the graphics, with adhesive applied after a final coat of white.

Because the panels sit in a fairly closely engineered place on the front panel... size counts. Slider cuts, led holes and the like need to be precisely aligned.

You will need drawings for the circuit layers, which need to be precise or they won't line up when the switch is assembled.

The silver ink needs to be cured or cooked for maximum lifespan You will need a spacer to hold the contact layers apart. That will want double sided adhesive applied to it, and should have "ventilation" cuts so that the spacer holes can "breath". Otherwise you will end up with some strange bumps in the panel if it gets hot. I can't be sure but for some reason the number "5mil" for the spacers seem right... but honestly it's just too long ago.

....all in all... have to say that I agree with David's approach and would try to locate a vendor familiar with doing prototypes for this kind of thing. They will have the screening and laminating gear necessary to reduce risk for this process...

David Clarke [21030085++]

I wonder if there are firms round the world competent to do that membrane re-creation...

Peter - there certainly are. Membrane keypads are still readily used in many environments (especially for industrial controls) - and there are many different options you can get (e.g., you can even get back-lit panels, or ones with built-in LEDs or LED windows).

Doing a quick net search for 'Membrane Switch' will show a lot of firms.

Many of these offer a 'prototype' service.

... - and of course how much they would charge, and what the minimum order would be.

Other companies have different pricing - but I would expect that for most the price will increase with the number of colours for the overlay, the number of cuts (if you'd like them to do it), the type of contacts (e.g., tactile/non-tactile) and thickness of material.

I could have perhaps searched around more and maybe found a better deal, but for the sake of confidence and a known working relationship, I ended up going to a company I had dealt with on other work (www.ezpcb.com).

I really only needed one (and perhaps a second for a 'spare'), so I was looking for the smallest order I could get. For the order I placed, there was a minimum order of 5 panels, and the total cost (which included them doing all the cuts, etc.) was $960, or just under $200 ea.

(For some odd reason I will actually pay more to fix a piece of equipment than I would ever pay for it in working condition...)

I suppose another question is whether replacement membranes' lifespan would be likely to be the same as the originals.

For the most part, the originals seem to suffer from a bad choice of materials for the 'tail' connections more than anything else. I would expect that new ones could last as long as the ones on the Chroma (vs. the Polaris) or longer, depending on the materials used.

And while I'm thinking out loud... how close did they get on yours to the exact colour and finish of the other membrane?

I provided them guidance on the colours - and tried to match my existing right panel. I wasn't perfect - but it's not awful either.

The one thing I didn't think of when ordering was the finish on the panel. The ones I got were a bit more glossy than the original.

I did veer away from the original a bit in that I preferred to have tactile switches instead of the non-tactile ones.

For me, I can now enjoy my polaris a bit more.

FYI, some pictures of the results as well as the trace layout are available here:

If I had to do over again I would likely go for a slightly thicker backing material and perhaps have a shorter tail attached.

If someone was serious about making a large quantity, then it would probably make sense to try to match the colour/finish more, likely by getting some samples of the panel panel. {Of course, if the panels were made in left/right pairs, then they'd only need to be consistent with themselves vs. an existing panel.}

Good luck with your repair!

Peter Forrest [21010096]

Another very thorough and helpful reply - thanks!

I'm keeping my fingers crossed that Keith can fix the ribbon; otherwise a more thorough solution like this seems worth at least exploring.

Peter Forrest [21010096]

Thanks to all for the excellent advice about the Polaris membrane.

As it happens, Keith at Lucid Sound has done a brilliant job, and managed to repair the ribbon so that the synth works perfectly.

So, short term at least, I won't be following up any of the ideas for a more thorough replacement of the whole panel.

One other idea that came up was that Technology Transplant (chipforbrains) in HongKong has apparently been selling Source membranes - and that maybe he could be a possible source of re-manufacturing and selling new Polaris / Chroma membranes if enough people expressed interest.

Peter Forrest

PS Because I bought it as part of a deal to get a Chroma as well, which was the main focus of the exercise, and the Polaris is now 100%, I'm reluctantly going to put it into my VEMIA auction this week. That way, I hope to re-coup my shipping and import expenses and contribute to the cost of the wonderful new bits I plan to get fitted in the Chroma - thanks to list members' hard work and endeavour.

YouTube

Chris Borman [21030194+]

Another Chroma on Youtube...

EPROMs on eBay

Chris Ryan [21030691]

Item #300362950292, 1 bid, current bid USD$33.33, ends November 4. "ARP Rhodes Chroma Rev. 14 Software set w/Kybd Scan IC."

Chris Ryan [21030691]

Sold for $33.33.

Re: Introduction and pressure sensor

Go to first message in thread, October 2009

Tom Hughes [21030251+]

Hi Chris (Borman),

I sent a Paypal payment of $355 the day you posted this (9/30) and I just received notice a couple of days ago that the payment was never claimed. I looked at the email address again and it says "FeedingTimer@Ccomcast.net" (see below). I just copied and pasted it, but looking at it again it looks like there's an extra C in comcast. Is that right? I'm wondering if anyone else has had the same thing happen.

I'm definitely still interested in the pressure sensor kit. I know there have been some changes in status since this original post, so I'm also wondering what the latest is.

Chris Borman [21030194+]

Pressure Sensor Update

Hi Tom, et. all,

The email address is incorrect. The correct paypal address is [address removed]. Thanks Tom for pointing that out! To update folks - The last issue I am having is with the opposing semi-conductive layer of the FSR. The vendor does not have the proper ink available at this time so I am looking at alternatives. I am going ask Sensitronics to produce the sensor. I've had many conversations with Frank and think I can work us a good deal.

arrived!

RJ Krohn [21030455]

hey folks, RHODES CHROMA 21030455 arrived last nite!!!! very excited. seller told me it needs a new PSU, so i have ordered one. (ps-im in philadelphia, pa, for registration's sake.) thanks-rj

Chroma for sale - California, US

Thomas Story [21030352]

I thought I'd just send a note out here first that I'm going to be putting my Chroma up for sale due to financial difficulties. I'll be posting pictures this weekend, but wanted to see first of there was anyone of the list looking for one.

It's had the power supply upgraded and the CC+ installed professionally and the whole thing has been gone over by a great tech near me. Everything works great. No case and I'm not psyched about shipping it anywhere, so that would have to be arranged by the buyer. I'm asking 2,300USD. IT really only need the wood refinished to make it sing.

let me know if there are any questions.

thanks

Apple II Card Hardware Description and Specifications

Chris Ryan [21030691]

I've posted Hardware Description and Specification, which is Appendix O from the Sequencer Manual. This details the Chroma/Computer Interface PC board for the Apple II, and includes the schematic and component layout drawing in PDF format, which were missing from the scan of the manual available at the site.

Jesper Ödemark [21010135]

You've heard it before and I've said it before, but it's worth saying again. Every vintage synth on the planet could use a dedicated homepage and a site manager like you Chris!

Great work!

"Voice Board Ultra RAR!" on eBay

Chris Ryan [21030691]

Once again (see Items on eBay Germany, September) we have a voice board available on eBay at the price of £655.00. But do not be too quick to judge: this is, if I'm not mistaken, the only "Ultra RAR" Chroma voice board I've ever seen for auction, and probably the only one in existence (RAR, I believe, stands for Retroactive Analogue Reanimator—and remember, this is the Ultra model). It's hard to believe that it wasn't picked up the first time around. It must enhance the Chroma in ways that a regular voice board, never mind a CC+, simply cannot. The oscillators are undoubtedly ultra rich, the tonal quality unsurpassed. In fact, with this piece of technology you probably would not even need any other voice boards in your Chroma, and the price reflects this, as it is at least eight times the recent sale price for voice boards. Indeed, if you actually had eight of these boards installed in your Chroma, you might be at risk of being paralyzed by the beauty of the soundscapes that would emanate from the instrument. So, one will be more than enough. I have attached one of the pictures of this amazing board; but be forewarned: gazing upon it for too long may initiate despair at the condition of your own lowly Chroma and its standard voice boards. After looking at it for just three minutes, I sold my keyboard along with the website for $5 on craigslist, as I realized that they had no value for me any more, since I can't afford the Ultra RAR board.

Item #280419011459, ends December 4.

Andrew Dalebrook [21010180]

LOL

Heheh..

It's not even a whitefaced ARP original.

Christian Kleine [21030210]

I can only strongly recommend to avoid this seller [ton-tornado], not only because of the phantastic prices but he's also a pain to deal with.

Matt Thomas [21010021]

:)

gotta get me one of those babies

Peter Forrest [21010096]

Funnily enough, he clearly does sell quite a few things.

I checked his feedback, and the one that stood out for me (pun intended) was a Doepfer Schaltwerk to a no-longer registered user 'nine-inch-cock' (-1).

It just got me thinking what happened to that inch.

Chris Borman [21030194+]

That character should team with the other ebayer who's listing the $840.35 Dual pedal... [item #290367608834]

I/O Board on eBay Germany

Chris Ryan [21030691]

Item #300365859681, starting bid USD$122.22, no bids yet, ends November 16. "It looks like everything is on the board but I have no idea if this works or not. If not, it could be used as parts."

Pictures from the auction:

For Sale by Steve Grom

Chris Ryan [21030691]

Steve Grom, Director of Marketing at Fender during the Chroma era and still with the company until recently, has decided to sell some of his Chromas and related items. See the registry entries for pictures. Contact him directly at [address removed] if interested.

Chroma Expander 16330138: This is in good working condition. I just had Paul Morte (Morte Technical Service in Orange, CA) replace some of the problem parts in the power supply. All the channel boards test fine and the cosmetic appearance is pretty good, considering it has lived without a case for most of its life. $2500.00.

Chroma #1, 21030690: Not working and does not power up. All parts are in place and original. This units suffers from the cosmetic problem of the foam lining from the anvil case is all over the outside of the cabinet

Chroma #2, 21030481: Basically the same as #1, not working and a bit more of a mess than the first one.

Regarding the two "project" Chromas, one issue is going to be shipping. They are both in cases (one original and the second a Rhodes Piano Flight Case). The cost will be fairly high. The ideal buyer would be someone who could pick the units up here in So Cal. Having said that, I have no problem working out the shipping details for any place there is a willing buyer.

Assorted power supply parts including three big blue caps and three transistors.

7 Channel Boards – 2 in un-opened packages from the factory, 2 test OK and 3 have error messages when installed.

Dual Footswitch – at least 1 and I think there is another in my garage somewhere.

Volume Pedals – 5

Small Square Footswitch – 1 and could be 2 or 3

Data connection cables – 2

CHROMA FIRST POWER UP! problems, though. can you help?

RJ Krohn [21030455]

hi folks, this is rj. i received my chroma a few weeks ago, and HOPE that i registered it properly.

anyway, i bought it on ebay, and the seller said it "works fine, but needs new PSU". i ordered a new PSU from luca, and it arrived yesterday. last night, i dropped it in, and powered her up for the first time. its not working properly, and am hoping for some leads on where i should look. the specs:

  1. the PSU installation seems to be proper. i added a 1A fast blow fuse upstream of the PSU. i measured all the voltages, and +/-12V, +5 digi, and +5 analog are all coming out proper. i trimmed +5 analog to 5.05, per the site's instructions.
  2. i removed the batteries from the old CPU board.
  3. upon the FIRST power up, i got a "!" at the top LED, and a wierd "4 @ 5" or something like that in the lower LED. i shut down, and powered up again several times, each time getting a random smattering of button LED's on, and no response from any of the buttons.

i was prepared for more than just a PSU replacement, so im not surprised that it needs more work than that. i have a CC+ board here that a friend lent me, but was waiting to install that until i got the unit working properly.

any suggestions as to where i should be looking? thanks alot, rj

Luca Sasdelli [21010226]

Hi rj,

the SPSU values are correct. I suggest to do the followings:

  • dismount CPU board
  • inspect all relevant cables and connectors for bent pins or insulation leaks
  • clean the connectors with contact fluid and compressed air
  • place the CPU board on a flat surface and firmly seat all socketed ICs (EPROMs etc.)
  • install new alkaline AA-size batteries
  • reinstall CPU board in place
  • reconnect all cables and be sure all plugs are firmly connected
  • remove all voice boards
  • clean all mother and voice boards connectors as above
  • insert only one voice board for testing

In this way the instrument should boot and initialize the only one card; if you're lucky and the card does work, you should see the logic to act as expected (e.g. patch select, A-B edit etc.). If so, check if [SET SPLIT][50] resets the instrument; if not, press the Reset button on SPSU PCB to see if the boot routine is done.

RJ Krohn [21030455]

great-thanks luca! i will proceed as below next chance i get to work on her!

Paul DeRocco [21030230]

  1. upon the FIRST power up, i got a "!" at the top LED, and a wierd "4 @ 5" or something like that in the lower LED. i shut down, and powered up again several times, each time getting a random smattering of button LED's on, and no response from any of the buttons.

So you're saying that the digital readouts have more than one digit turned on? Since it's a multiplexed display, that can only happen if the CPU is running more or less normally. If the CPU is crashed, you'll see either nothing in the digital readouts, or some random segments turned on in a single digit.

I second Luca's notion, to check connectors, including socketed parts. Since you're having problems with both the display and the switches, I'd suspect the tails that connect the CPU board to the big I/O board.

RJ Krohn [21030455]

ok, here's the update:

  1. i cleaned all harness connections on all of the under-panel boards-CPU, EQ, and middle board. reseated. removed all voice cards, cleaned harnesses, and reseated voice card 0.
  2. upon powering, it did the exact same thing it did the first time: the FIRST power up gave me "!" in upper readout, and digit count in bottom readout. it would respond to some of the button values, but then froze after about a minute. the 2nd-10th power up gave me NO values at the readouts, and no responses from any of the buttons.
  3. fyi, the battery holder is shot; i wasn't able to replace it.

any thoughts? thanks for the help.

David Clarke [21030085++]

  1. fyi, the battery holder is shot; i wasn't able to replace it.

If the original CPU board looks like the original battery leaked, then there could be damage on the CPU board itself preventing proper operation. While that can likely be repaired, if there's access to another CPU board that is known good (or a known-good CC+ board), then it is worth the quick try to evaluate the behaviour with the alternate CPU installed.

RJ Krohn [21030455]

i do have the CC+ board here that i believe is known to be working. i will try dropping it in, and see what happens.

RJ Krohn [21030455]

problems,_though.....CC+, 1 voice card. what does this readout mean?

hi folks, so i installed the CC+ board i have here, and stuck w/ just the voice 0 slot occupied for voice cards. upon power up, i am getting response from SOME of the panel functions, but not all. i can't seem to select "pgm change", unless i press one of the cassette function buttons first. (maybe that's normal?) i was able to select the split functions. the parameter slider gives the "knock". what do these values mean in the data readout?

2

8'8 2 6 7

im also getting no sound, but about 2/3 of the 50 preset/membrane location buttons are responding.

should i load more voice cards and see if i can get some sound? or is this normal function, and next step is i need to learn how to program the thing? thanks for the help.

Luca Sasdelli [21010226]

Re: problems,_though.....CC+, 1 voice card. what does this readout mean?

Hi rj,

here you'll find an explanation of the CC+ display readouts: Expansion Board and New Firmware: Features

Since your description, I guess there should be something failed in the wiring between front panel and CPU board. Therefore I suggest to do the same dismount & cleaning as I wrote, on front panel cables; the digital management (CC+) is brand new, therefore all panel devices should work properly. If not already done, have a check also on I/O board and motherboard at same way.

After that, even if you'll take apart the full keyboard for (generically needed) vacuuming, you'll be entitled as a "Chroma Expert" :-D

Away from yokes, I think that, if such as a malfunction exist, it is better to take apart the whole thing, reviewing all connections and socketed components and reconnect all parts with lots of care, and schematic diagrams at hand.

If you can map exactly which buttons are failing, I can check the schematic for a possible cause.

Paul DeRocco [21030230]

Re: problems,_though.....CC+, 1 voice card. what does this readout mean?

here you'll find an explanation of the CC+ display readouts: Expansion Board and New Firmware: Features

Since your description, I guess there should be something failed in the wiring between front panel and CPU board. Therefore I suggest to do the same dismount & cleaning as I wrote, on front panel cables; the digital management (CC+) is brand new, therefore all panel devices should work properly. If not already done, have a check also on I/O board and motherboard at same way.

I agree. If there are problems with both the switches and the display, I'd suspect a problem with one or more of the data bus lines between the CPU board and the I/O board.

RJ Krohn [21030455]

Re: problems,_though.....CC+, 1 voice card. what does this readout mean?

ok, here's where i'm at:

  1. EVERY harness on the I/O board has been removed, cleaned, and replaced. (im assuming J24 is occupied, and J22, is free? this was how it came; i see schems show J24 as output on I/O, but no J22 pinouts)
  2. the harnesses from the CC+ board to I/O were checked, pin by pin, for continuity. they are all seated.(as an aside, i noticed that i got higher impedance measurements between 2 adjacent pins;example being pin 2-pin 3 would sometimes show about 40ohms)
  3. the program select buttons that DONT work are the 3rd and 5th of each "set", 20-25, and 30-35. so 3,5,8,10,13,15,18,20-25,28,30-35, 38,40,43,45,48,50 dont work.
  4. when i go to location 37 and depress keys, i get nada. the readout says "A.2        8".
  5. also, the knocker thing will periodically sound when the machine isn't being touched.

there dont appear to be any more harnesses anywhere that i can clean and reseat. any thoughts? thanks so much for your help, guys!

Dave Blees [21030552]

Re: problems,_though.....CC+, 1 voice card. what does this readout mean?

Yo, Luca! If you are indeed shipping power supply units, I should ask what may have become of the one I paid you for last month?

Hoping to hear from you someday...

David Clarke [21030085++]

Re: problems,_though.....CC+, 1 voice card. what does this readout mean?

(im assuming J24 is occupied, and J22, is free? ...

Correct. J22 is the connection for the pressure sensor. If you don't have one (as most don't) this spot will be left empty.

J24 is the connection to the channel motherboard.

  1. the program select buttons that DONT work are the 3rd and 5th of each "set", 20-25, and 30-35. so 3,5,8,10,13,15,18, 20-25,28,30-35, 38,40,43,45,48,50 dont work.

The switch assignments can be checked out in the table at the end of IOSTROBE.DOC [82K Microsoft Word document, from the EPROM Code page].

  • The problem on every 3rd item seems to be a problem with -SW2.
  • The problem on every 5th item seems to be a problem with -SW4.
  • The problem on 20-25 seems to be a problem with -STB8.
  • The problem on 30-35 seems to be a problem with -STB3.

If -STB3 and -STB8 have issues, I would also expect problems with other buttons like Link Upper and Edit A/Edit B.

These signals go to the panel on J14 and J15, two of the flexible cables at the bottom middle of the I/O board. I would double-check these for connection, potential breaks, shifted to the side, or anything awry.

If you have a simple ohm-meter, then with the Chroma off, you can use the connection matrix in the referenced document, and check to see if it is indeed a switch/connection issue (e.g., connect one end of the meter to -SW0, the other to -STB0, press the "1" key, and see if you can detect the press).

the readout says "A.2        8".

The readout should normally say something like "P1       8".

The "A" and the "P" would be really the same, with just an extra segment lit up. (Segment "C", also as shown in IOSTROBE.DOC).

The 'dot' is likely correct, as that is used by the CC+ to indicate which patch bank should be used.

The "2" could be correct, depending on which parameter is pressed. It would be interesting to see if the values in the display change as you either press other program buttons, and/or as the slider is moved.

  1. also, the knocker thing will periodically sound when the machine isn't being touched.

There are a few possible reasons for this. One to be ruled out will be whether there is an intermittent switch panel connection. Key to this will be to press one of the panel keys so that the decimal point of the large LED display is extinguished (e.g., the 'program modified LED'). Once out, let the machine sit and wait for the panel to knock by itself. Now look at the displays and see how/if they've changed. If you now see a different number in the big display, then the Chroma thinks that that program button has been pressed.

RJ Krohn [21030455]

Re: problems,_though.....CC+, 1 voice card. what does this readout mean?

thanks so much! i tested some things, answers below(not sure where to proceed to now, though!)

"If -STB3 and -STB8 have issues, I would also expect problems with other buttons like Link Upper and Edit A/Edit B."

yes. that's right. autotune doesn't respond, among others.

Luca Sasdelli [21010226]

Re: problems,_though.....CC+, 1 voice card. what does this readout mean?

D'Ett'n'Dave ha scritto:

Yo, Luca! If you are indeed shipping power supply units, I should ask what may have become of the one I paid you for last month?

Hoping to hear from you someday...

Hi Dave,

I've just received the last batch of SPSUs from my supplier; the kit should be shipped tomorrow.

Heinz Weierhorst [21010276]

Re: problems,_though.....CC+, 1 voice card. what does this readout mean?

Hi.

I'm a Chroma owner too and hope I can help a little. When you power up the Chroma do all leds on the left control panel flash?

If yes the databus seems to be connected right and the CPU is doing something.

If not you have to check both ribbon cabels and the connectors J-9 and J-10 coming from the CPU to the IO board.

[A 5/6] coordinates as given in IO board assembly sheet.

J10-15 A3
J10-14 A2
J10-13 A1
J10-12 A0
J10-11 BATT
J10-10 B7
J10 -9 B6
J10 -8 B5
J10 -7 B4
J10 -6 B3
J10 -5 B2
J10 -4 B1
J10 -3 B0
J10 -2 !IOWR
J10 -1 !IORD

[A 3/4] see above

J9-15 2MHZ
J9-14 !KINT
J9-13 !8MHZ
J9-12 8MHZ
J9-11 !XOINT
J9-10 !XIINT
J9 -9 !RES
J9 -8 +5D
J9 -7 +5D
J9 -6 +5D
J9 -5 +5D
J9 -4 DG
J9 -3 DG
J9 -2 DG
J9 -1 BUFF DG

Everything ok?

Now what I am assuming: Because have you trouble with both the control panel scanning and the display scanning there only two or three commen components.

Check connections:

[I/J 2]

Z12 -9 !WRSDS from Z40-10 [E/F 4/5]
Z12-13 B3 from J10 -6
Z12-12 B2 from J10 -5
Z12 -5 B1 from J10 -4
Z12 -4 B0 from J10 -3

Z12 is 74LS175; Quad Latch.

[J/K 2]

Z13

Check all pins from 1 to 11 with a scope. They must go low in a sequence!

Z13 is 74LS145; Decimal Decoder; Outputs active LOW.

If don't at least check Z40-10 [E/F 4/5] with a scope. Is there as short low going pulse appr. 300nsecs?

So if you don't have a scope try to replace Z12, Z13 first and then Z 40. Be carefull when removing - don't kill vias! Put the the circuits in very good sockets.

Good luck!

Paul DeRocco [21030230]

Re: problems,_though.....CC+, 1 voice card. what does this readout mean?

Two more possibilities: it could be that there is more than one problem, e.g., a damaged membrane switch tail and something wrong with the display driver. You can't always assume, especially in something really old, that all the symptoms point to the same place. Second, it's important to remember to check for shorts, not just opens. I've seen digital lines shorted together, which produces different symptoms from an open line.

This sort of problem is almost impossible to diagnose without a scope and a good understanding of how the circuitry works. A decent service tech with the right tools ought to be able to track the problem(s) down pretty quickly. Flying blind, you might be able to fix it, but you might burn up a lot of hours trying.

Lars Johansson [21030632]

Re: problems,_though.....CC+, 1 voice card. what does this readout mean?

This sort of problem is almost impossible to diagnose without a scope and a good understanding of how the circuitry works. A decent service tech with the right tools ought to be able to track the problem(s) down pretty quickly. Flying blind, you might be able to fix it, but you might burn up a lot of hours trying.

Seconded but, you will learn a lot from it. It takes time ( and money ) trying to repair complex instruments like the Chroma.

I'm servicing a Fairlight CMI IIx now and I made a decision to not try to repair the battery damaged CPU card. It was way too timeconsuming and the potential of getting to work was not good. I bought new cards instead of wasting time on it.

RJ Krohn [21030455]

Re: problems,_though.....CC+, 1 voice card. what does this readout mean?

hi folks, so i have verified that Z12, Z13, and Z40 are NOT the culprits here. i have socketed and replaced them, and the behavior is identical. i have also cleaned all of the ribbon harnesses at the bottom of the I/O board.

so it sounds like i need to start checking on a scope. while my scope is older, i can give it a go, and hopefully make some progress. so where should i be measuring, and what should i look for? Heinz, you were correct that i am also having the exact button problems that you guessed on the left control panel!

thanks much for the help.

Paul DeRocco [21030230]

Re: problems,_though.....CC+, 1 voice card. what does this readout mean?

The digital signals aren't too fast, so you don't need a very wideband scope. And while it's nice to have a "real" scope that has triggered sweep, even one of those old TV service things that's only able to sync to vertical or horizontal sweep can still let you look at a digital line and see the discrete levels, i.e., near 0V for logic 0, around 3.5V for a TTL logic 1, 5V for a CMOS or resistor pull-up logic 1, maybe 2.5V for tri-state with TTL loads on it, and something like 1.5V if two lines are shorted together and pulling against each other.

To really diagnose the problem, you need to trace the whole switch/display scanning stuff. Make sure all four Z12 outputs are moving; it actually counts 0,1,2,3,4,5,6,7,8,9,8,9,8,9,8,9 in a 20ms cycle. The decoded outputs of Z13 aren't so easy to analyze because they're open-collector, and thus don't go high except to the extent they're pulled up by the displays, which only happens if one or more segment is driven high, or the switches, which only happens when you press on a switch. Make sure the display segments outputs on Z15 are all moving, which should happen as long as at least one of each segment (including decimal point) are on in some digit somewher.

As to switches, the same decoder is used, but the switches are read back in via Z16. The inputs should normally all be around 5V, but you should see pulses to ground every 20ms if you hold a switch down. If one or more doesn't work, then the membrane switch tail is probably bad. If they all move correctly, then the problem may be Z16, or a shorted or open data bus line (B0..B7).

If you think logically about it, it shouldn't be too hard to narrow the problem down.

Footswitch on eBay

Chris Ryan [21030691]

Item #300369077028, Starting bid USD$22.22, no bids yet, ends November 22. "It is a stereo type cord and the make/break contact is between the tip and the ring. The sleeve must be the ground connection. Not parts have been replaced and it was tested to work in the above described mannor."

Picture from the auction:

Chris Ryan [21030691]

Sold for USD$22.22.

Chroma Pressure Sensor Project update

Chris Borman [21030194+]

Hi All,

Status update on my Chroma Pressure Sensor project - I mentioned before I was having a problems with the actual sensor and so decided it would be best to work a deal with Frank/Sensitronics to help produce the Sensor Array. He so graciously offered to assist! I am just about ready to start ordering parts and will go ahead and invoice folks who expressed an interest to get started. I was looking for a production run of 10 to hit quantity discounts. Let me know if anyone else is interested! Chris R. should have an info page up on the website in Dec. with schematics, PCB and FSR sensor array drawings, installation instructions, theory of operation and mock-up hardware installation pictures.

For Shipping, USPS offers International Flat Rate to any country for $12.95 in a flat rate box 8 5/8 x 5 3/8 x 1 5/8, up to 4 lbs. The actual sensor is the biggest part of the kit. Being flexible, It should roll up and fit right in there! Total weight will is <2 lbs. Anywhere in the states is about half that or $4.95. And the best part about USPS is the box is included!

So the total cost is $345 + Shipping. Lead time will be 3-4 weeks ARO. $30 value for international folks?

The correct Paypal address is [removed] (Thanks Tom H. for pointing out the error in my prior note!)

Peter Forrest [21010096]

I'm very interested, please, Chris. In fact please count that as a definite. I'm in England.

Dave Manley [21030547]

Hi Chris,

Sorry if this has already been discussed. Has a prototype been tested and known to work? How much risk is involved in signing up?

Daniel Rickenbach [21010172]

Hi Chris

let me know, when you expect the money, I'm already interested.

Paul DeRocco [21030230]

Chris,

I'm certainly interested, but I have two questions. First, does this just plug into the existing jack on the I/O board, and work with the standard Chroma firmware? Second, how do you make a sensor that is flexible? Doesn't it need to have some multiplexors, etc., to interface to the I/O board? Is it made out of Kapton flex circuit or something like that?

Chris Borman [21030194+]

Sorry if this has already been discussed. Has a prototype been tested and known to work? How much risk is involved in signing up?

Hi Dave,

Electrically this new design is much simpler and the actual sensor more robust than the original unit installed in the Chroma. Force Sensing Resistor (FSR) pressure sensors have been around for 20+ years and in fact the inventor of the FSR, Frank Eventoff himself, is assisting with this sensor design and production. That leaves the analog multiplexing circuitry which is pretty straightforward stuff and in this case requires minimal parts. Getting a pressure sensor to work is pretty straightforward as well. This is just another implementation. I've goofed with FSR sensors a bit in the past and coincidently have a very special Digital Percussion Controller in the works based on the same FSR technology, but a more involved implementation and supporting circuitry smarts requirements. In this case the first ten will be in effect the prototypes.

The risks are a circuit or PCB layout snafu, picking a part that can't be obtained or to the extreme, me getting hit by a bus.... Snafu's are fixable. There are always other parts to choose from (CEMs not included), and I always look both ways before crossing the street! If all three happen to happen, I might take that as a sign to quit and as a last resort would refund your money. So all in all, not that big of a risk!

Ken Ypparila [21030229]

I have a hand built one in mine using FSR and wirewrap boards. I put the FSR strips under the felt. This was back in 1985.

Chris Borman [21030194+]

Plugs right into J22 on the I/O board and works with the existing firmware. David C. [21030085++] mentioned the CC+ recognizes polyphonic pressure for local modulation, but requires and will be updated to transmit MIDI poly pressure. In my implementation, the sensor circuit is based on flexible mylar. Kaptan is a higher heat tolerant substrate for specialized ink application methods not required here (unless Frank tells me otherwise). In this case the sensor assembly, there's actually four 16 key sensor arrays, will be layered with felt and double sided foam rubber and attached to the bottom of the damper bar. Each of the four sensor arrays have FPC type connector tails that plug directly into FPC connectors on 3 mini mux PCB's mounted to the side of the damper bar, that jumper together and then to J22. A real simple design. My only wish is consistent .5mm circuit resolution, then it would have all fit on a single PCB (I suppose that could be marked up as risk #1 successfully overcome!).

Chris Borman [21030194+]

Hi Ken, I believe I talked with you way way back in the 80's! Same design here, just a custom FSR array and laying out the electronics on a PCB.

Ken Ypparila [21030229]

It should work, I don't remember there being any problems. There is a special connector I had to get that you could insert the plastic tails into.

Go to next message in thread, December 2009

it's getting worse...

Jesper Ödemark [21010135]

Hilarious price!

[eBay item #290367608834, dual pedal with asking price of £500.]

Pictures:

Luca Sasdelli [21010226]

And as dirty as shown! Think what could be the price if clean :-)

Jesper Ödemark [21010135]

Does this mean that you want to buy my clean one? I'll even polish it for you and include postage. :)

Heinz Weierhorst [21010276]

A very fair price. 300 BP is about € 332. For new double pedal (not the badest) you will have to pay € 45! But it's clean without that patina of the years!

CC+ 6th batch

Sandro Sfregola [21010294]

Notification of Planned Chroma CPU plus (CC+) 6th batch

We have once again placed enough people on the CC+ 'wait list' to justify another build of boards.

Due to different personal schedules, for this batch the orders will be handled differently by Sandro and David (for practical and economical reasons we have different sources for some of the CC+ parts).

Sandro has already contacted his "European" customers that were on the wait list and has started to collect payments. If you are located in Europe and interested being included in this upcoming build please, contact Sandro as soon as possible.

For other customers David will accept orders for this sixth build up to Saturday, January 2nd, 2010 (midnight, Eastern Time). To ensure a timely order of parts for those who have requested CC+ boards, payment is required to be received by Saturday, January 9, 2010.

NOTE: With over 100 CC+ units already built and shipped, many of the interested users have already ordered. This tends to mean that new requests have slowed - causing the wait list to take longer to fill. That being the case, people being put on the wait list are having to wait longer and longer to get their units.

If you have been considering getting a CC+ unit and do not wish to wait for an extended period, it may be worth-while considering being included on this upcoming build.

On December 12th David will be individually getting back in touch with the people on the wait list - to re-acknowledge that you're on the list.

David will send out another note to those on the wait list on January 2nd to confirm your order. If you're not currently on the wait list but would like to have a board from the 6th build, please be sure to get in touch before January 2nd (preferably sooner).

If you believe you're on the wait list but do not receive an e-mail from David on or near December 12th, be sure to let him know.

Thank you for your continued interest and participation.

Sandro Sfregola [21010294]
David Clarke [21030085++]

Progress with my Chroma!

Frank McGing [21010198]

I picked up the I/O board that was on eBay recently (it's an early ARP board), and installed it a short time ago to see if I could get any further with my non-functional Chroma. It was complete, apart from a missing keyboard scan EPROM, which I took from my own I/O board. Lo and behold, my Chroma woke up! Well, not quite - the LEDs only flash once, so it doesn't appear to be tuning any of the voice boards, but I'm getting '1' in the upper display, and 01234567 in the lower one, which is a big improvement over random LEDs stuck on at boot. The good news is that all panel buttons are responding, the parameter slider is working, and so is the tapper. I tried SET SPLIT 50 but it didn't successfully tune any voice boards. But all panel functions appear to be working.

The bad news is that I can't get the trimmer offset voltage any lower than 330mV (fully anticlockwise), and in its centre position, it's showing .5V between the test points. I was able to get my original I/O board to 0V without any difficulty. Also, the lower display is missing rather a lot of segments.

At this point, I'm not sure of the best way to proceed. Now that I have confirmed that the original I/O board is faulty, I could go ahead and try to diagnose it, or I could stick with the ARP board, try to solve the .5V offset problem and switch the lower display from the original board. I'm inclined to go with repairing the original board and keep the ARP as a spare, but I'd appreciate any feedback!

Paul DeRocco [21030230]

The bad news is that I can't get the trimmer offset voltage any lower than 330mV (fully anticlockwise), and in its centre position, it's showing .5V between the test points. I was able to get my original I/O board to 0V without any difficulty.

Well, there you go, that's your main problem. If the DAC doesn't work then nothing will tune properly. First of all, make sure that the DAC GND reference coming from the Channel Motherboard is actually connected, by verifying that TP0 is very close to some other ground reference (e.g., digital ground on Z23-10). If that's okay, then it's most likely a burned out Z25, the TL081 op-amp, but it could also be the DAC itself if it's totally fried.

Also, the lower display is missing rather a lot of segments.

Really? But none of them were missing in the 01234567? All of the segments appear in at least one of those digits, so that means the segment (anode) drivers all work. And since all of the digits showed something, that means the digit (cathode) drivers all work. The only other possibility is that some of the actual display segments have failed, which is something I've never seen. But you could scrounge the display from the other board if that's the case.

It sounds like the ARP board is closer to working, so try to fix that. Good luck.

Go to next message in thread, December 2009