ChromaTalk Archives: October 1999
News
Chris Ryan [21030691] · Fri, 15 Oct 1999 22:55:57 -0700
The list has been down for a couple of weeks, I think. My ISP fixed the problem today, but I'm not sure whether they'll be able to recover any messages sent. So if you did send something and it didn't get through, try again now.
I'm moving home to Canada and will move the Chroma site to a new location. I'll let you all know when it's done. I don't expect the pages or the mailing list (to which I'll automatically subscribe all of you) will be down at all; I'll just switch it over one day when I get settled in Vancouver.
Thanks,
Chris
Power Supply vs. Capacitors
Chris Ryan [21030691] · Wed, 20 Oct 1999 07:36:09 -0700
My Chroma is in the shop right now (CAE Sound in San Mateo, California). I wanted to get a new power supply installed before I move to Canada, as there are no Chroma techs left back home.
CAE Sound called me yesterday. They say there's nothing wrong with the power supply (I knew that), but I might want to replace the capacitors (on the power supply and voice boards) because they're getting old. Do I need this work done? Would the power supply would last, say, another ten years with new capacitors? Why would the voice boards need to be "re-capped"? I wanted to get the power supply replaced as preventative maintenance, but now I don't know what to do.
I'd really appreciate any advice.
Chris
Kurt Otto [21030572] · Wed, 20 Oct 1999 09:43:42 -0500
I believe "re-capped" means new capacitors for the voice cards, too, so its new caps all the way around. I just got a MAP80-4000 power supply ($135) from my local Carlton-Bates outlet, but I haven't started screwing with it yet.
Don Tillman · Wed, 20 Oct 1999 08:21:00 -0700 (PDT)
My Chroma is in the shop right now (CAE Sound in San Mateo, California). I wanted to get a new power supply installed before I move to Canada, as there are no Chroma techs left back home.
Canada?!?! (Motto: "Technically, a nation.")
(That's from Dave Barry of course.)
CAE Sound called me yesterday. They say there's nothing wrong with the power supply (I knew that), but I might want to replace the capacitors (on the power supply and voice boards) because they're getting old. Do I need this work done? Would the power supply would last, say, another ten years with new capacitors? Why would the voice boards need to be "re-capped"? I wanted to get the power supply replaced as preventative maintenance, but now I don't know what to do.
"Recapping" is an operation done in Hammond organ circles. On the Hammond there are older-technology capacitors (paper and oil, but that's a guess) on every pickup for shaping the waveform. After some time, twenty years or so, the dialectric in the those older caps starts to chemically break down, the cap's value drifts up, and the organ starts sounding really dull. All Hammonds with the original caps should be "recapped" with modern ones.
But the caps in the Chroma voice cards are all pretty modern and high quality. They probably won't show this problem for a century or so, and then the effect would be that some of the boards would pitch too low to auto tune consistantly. (And lots of other things can cause the machine not to auto tune consistantly, but you knew that.)
I don't think there's anything in the Chroma power supply that would really age. Maybe the big honkin' power supply cap, but even that shouldn't be a problem.
-- Don
David Clarke [21030085++] · Wed, 20 Oct 1999 11:29:19 -0400
CAE Sound called me yesterday. They say there's nothing wrong with the power supply (I knew that), but I might want to replace the capacitors (on the power supply and voice boards) because they're getting old. Do I need this work done?
Electrolytic capacitors (like the big one in the centre of the power supply) actually dry-out over time, reducing their effectiveness. In terms of impact to the actual performance to the Chroma, this could/would mean ripple/noise coming through on the power supply lines to the rest of the keyboard (and could cause improper operation of the keyboard if the situation got bad enough).
The caps will dry out with age, but also with heat - so the amount of time the power supply has been on and running is a factor to take into consideration too.
The tech should be able to look at the output of the power supply and determine if the cap(s) need to be replaced now. If things are OK now, it will then be a judgement call if you want to replace it/them anyway. It can't hurt to replace the power supply electrolytics now (other than in the pocket book). On the other hand, such a procedure is very much a straight-forward job, so even if you waited and then had them changed sometime in the future, a general electronics tech should be more than up to the challenge.
My personal feeling on the voice boards is that if they're working OK now, then I'd leave them alone.
Dave
Chris Ryan [21030691] · Wed, 20 Oct 1999 09:11:13 -0700
At 8:21 AM -0700 1999/10/20, Don Tillman wrote:
Canada?!?! (Motto: "Technically, a nation.")
(That's from Dave Barry of course.)
Wow, that's a low blow! Canada is a wonderful country, with a higher standard of living than the U.S. (voted 'best country in the world' several years running by the UN). And quite independent. You should visit some time. :)
I don't think there's anything in the Chroma power supply that would really age. Maybe the big honkin' power supply cap, but even that shouldn't be a problem.
I thought this was the Achilles' heel of the Chroma. Your article (www.till.com/articles/ChromaPowerSupply/) points out a whole bunch of problems, and other list members have had theirs die. I thought I'd be preemptive about it, but I don't want to waste money, either.
At 11:29 AM -0400 1999/10/20, A. Gordon Clarke wrote:
The tech should be able to look at the output of the power supply and determine if the cap(s) need to be replaced now. If things are OK now, it will then be a judgement call if you want to replace it/them anyway. It can't hurt to replace the power supply electrolytics now (other than in the pocket book). On the other hand, such a procedure is very much a straight-forward job, so even if you waited and then had them changed sometime in the future, a general electronics tech should be more than up to the challenge.
What are electrolytics?
Chris
Don Tillman · Wed, 20 Oct 1999 11:02:24 -0700 (PDT)
Wow, that's a low blow! Canada is a wonderful country, with a higher standard of living than the U.S.
Hey I was kidding. After all, Canada is home to Alanis Morissette. :-)
(Sorry, I can't help it. Ever since Second City TV was told by their station that they had to have a certain percentage of "Canadian content" in their show, it's open season!)
I thought this was the Achilles' heel of the Chroma. Your article (www.till.com/articles/ChromaPowerSupply/) points out a whole bunch of problems, and other list members have had theirs die. I thought I'd be preemptive about it, but I don't want to waste money, either.
Yes, but the problems with the Chroma power supply are due to its fundamental design, not aging components. If you have one that's working for you, you'll probably do okay and additional years of use shouldn't make it any worse. If you get a new Chroma power supply, you're looking into the murky depths of infant mortality issues. And since infant mortality issues can be extra plentiful with a flawed design, my gut feel is that you don't want to go there.
What are electrolytics?
A type of capacitor optimized for high capacitance values in a reasonable space. That big blue can in the power supply? That's one. Power supply 'lytics can be large like that. Smaller 'lytics used in regular circuitry are typically the size of a thimble.
-- Don
Jimmy Moyer [21030184] · Wed, 20 Oct 1999 15:25:14 EDT
While the big electrolytic caps can dry out over time this is most likely to happen because of disuse over a period of years. Even if that happens, you can sometimes 'reform' them if you bring the line voltage on the unit up slowly over serveral hours. There should be no reason to replace them preemptively. (Sitting here, listening to my 35 year old Dyna ST-70, that's been rebuilt over the years, but the electrolytics are still original.)
Likewise, I agree, no reason to recap the voice boards. Those should last a long time.
BTW, one thing which I have done to my Chroma, is to take the paint off the back panel between power switch and the jacks and bolt on an aluminum heat sink, ala Prophet 5. Always wondered why they never did that originally.
-> Jimmy
Jerry Leonard [21030100++] · Wed, 20 Oct 1999 21:00:29 -0700
Chris, I've completed putting in a new MAP 4000 power supply and built a
reset circuit designed from the original schematic. It works great. I
have a copy of the reset schematic I could send to you. If you have some
questions, I'd be happy to pass along what I learned when I made the
switchover. There were many things to learn, but all in all, it was kind
of fun. (I was just up in Victoria last week. Beautiful city.)
JL
Chris Ryan [21030691] · Sat, 23 Oct 1999 13:40:27 -0700
Thanks, everyone, for all your advice. In the end I had to make a snap decision, and told CAE Sound to go ahead and recap the power supply but to leave the voice boards alone. I picked up my Chroma yesterday and they did a wonderful job on refinishing the instrument; it hasn't looked this good since it was new. No more goop: the wood looks great--they used something called "tongue oil" to finish it. As for the other repairs, it's hard for me to judge, but the instrument was plugged in when I got there and played well (except for the old problem of the occasional intermittent key).
So I'd have to say I'm happy, as long as the old power supply is OK. I shouldn't be one to balk at a company who says, 'you really don't need this work done.' It's usually done in honesty. (And I spent $350, not the originally quoted $650.)
Peter at CAE told me that, if I got together a number of people who want new power supplies, he might be able to get the price down (he implied that he'd have to do some custom building, so I assume his original quote was a bit low). Certainly I don't know of anywhere else that has such an extensive supply of Chroma parts (and Chromas: I saw his Expander, whose main board is damaged by leaking batteries; and he has two others, one for parts and one that "almost" works).
Chris
Eirikur Hallgrimsson [21030467+] · Sun, 24 Oct 1999 06:17:16 -0400
I have no problems with intermittant keys. The Chroma's key contacts are just hanging out in the open air, waiting for gunk to land on them for whatever reason. My general approach to all 'exposed contact' issues is to treat them with Caig Labs "DeOxit." That's the new-fangled name for Cramolin. I use the R5 5% spray. I've fixed probably dozens of synths with it. It's ideal for scratchy pots (knobs that make crackling sounds).
Eirikur