[sdiy] SSM2055 ethics

rsdio at audiobanshee.com rsdio at audiobanshee.com
Sat Jul 11 22:06:47 CEST 2015


I see your point, Tom, and if we had no additional information then I wouldn't feel compelled to reply. However, the industry manufacturers have a policy of marking chips as "NRND" - Not Recommended for New Designs - when their plans to continue the chip start to see an end that might affect their customers. In addition to the public markings of particular chips as NRND, professional product design companies have buyers who negotiate directly with chip vendors to secure volume discounts, get advice on chip trends, and basically to build a partnership between chip maker and product manufacturer to lessen the sorts of uncertainty that is normal for the high-tech industry.

Yes, obsolescence is part of the system, but that doesn't mean it's a totally unpredictable game of chance with no clues anywhere.

To respond to your example; if the 741 were truly obsolete, then the manufacturers would mark that chip as NRND and would eventually stop making it. Despite your opinion that it is old and obsolete, it clearly still makes sense for chip makers to continue manufacturing that part. With at least four different companies making the 741, I'd say you're perfectly safe designing a new PCB that uses the venerable 741.

Getting back to the example of the SSM2055, I'd say that when a company no longer exists, you have a situation where the warnings are even stronger than an active company marking a chip as "NRND."

Note: One thing I forgot to mention about designing new boards to use chips like the SSM2055 that might be better saved for repairs is this: If there are any mistakes in a new design, then there is a risk that the SSM2055 could be blown up. So, even with sockets on the new PCB, there's still a non-zero chance that some future repair will end up with sad news because the limited vintage chip supply was reduced by an avoidable mistake.

Brian


On Jul 10, 2015, at 11:16 AM, Tom Wiltshire <tom at electricdruid.net> wrote:
> True, but if the chips are there now, and no-one's doing anything with them, it seems a shame to waste them! Anyway, isn't obsolescence simply a part of electronics? How many designs survive more than a couple of decades? Even the few that do (you can still buy a 741…) are mostly clearly obsolete. I've designed replacement env gens around current PIC parts, but within a decade or two those won't be available, and it'll be time to redesign for the available chips of the future. That's simply the nature of the business. Work with what you've got in your parts drawer, since that's what's available to you right now. If that includes old SSMs that you haven't got any other good use for then go for it. Just don't order a hundred PCBs if you've only got five chips.
> 
> I had several 2056's hanging around at one point and had this same debate with myself. I'd been given a dead Polysix which I cannibalised for parts to keep my own Polysix running. Eventually I was contacted by someone else in a similar position, and I sold them the missing env gens they needed, which saved me debating further, and meant that my one dead Polysix had saved at least two others.
> 
> However, this process of cannibalising parts means that instruments with common serious failures ( like the battery leakage problem ) are only going to get rarer and rarer. Polysixes were cheap once - I bought mine for $100. God knows what it's cost me since then in time and effort! You can't find them at anything like those kind of prices now, and I suspect there are many less than there were then too, given their reliability, or lack thereof.
> 
> Tom
> 
> On 10 Jul 2015, at 17:46, rsdio at audiobanshee.com wrote:
>> Here's one way to look at it:
>> 
>> One day, these chips will be gone, and designers will have to learn how to design circuits that perform the same functions using new parts. I figure that you might as well start the process of learning how to design with new parts now, rather than build a bunch of PCBs that can't be used once the chips they were designed for are not available. If you design with modern parts, your boards won't become obsolete when the old chips are gone.
>> 
>> Brian
>> 
>> 
>> On Jul 9, 2015, at 12:23 PM, crystal <crystals at sonic.net> wrote:
>>> now i'm having second thought about building a new modules with two of these chips. are they really needed for repairs of old synths? i was just about to start building a dual VcEnv Gen with some extra features (not chip specific) like peak out and cycle.
>>> my other option is to modify the Ian Fritz AD/AR Env Gen with a few vactrols. i built one as is and it's are a great circuit.
>> 
>>> On 7/3/2015 1:26 AM, crystal wrote:
>>>> can someone point me to data sheets for the SSM2050 and the SSM2055. i've searched and come up with most of the other SSMs but not the two i actually need.
> 


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