Just venting..lol
I'm also an electronics engineer and I understand the situation regarding schematics in the public domain. But I stand by my statement about the SDS7..it's physical design is terrible. I simply moved mine from the rack it is in to the workbench...bang it stopped working. Took the top off, reseated the CPU and memory card and it's all ok again. That's my point. Even though I acknowledge the units age etc it is simply too fragile to be used in a gigging format. (even from new..this has been confirmed to me by people who did try to cart them around way back then)
I recently had an email with a well known chap here in Oz (makes a highly regarded series of mods for the TB303) and he said he was servicing the SDS7's when they were new and they had the same reliability issues back then. He agree's the hardware design is poor.
Given that it was a big ticket item back then and given the ability to use hindsight, better PCB to backplane connectors really wouldn't have added too much to the cost. I have fixed a number of SDS7's and they all had the same problems. As an engineer, this indicates to me a flaw in the design. I guess had Simmons survived, these design changes would have filtered through due to gradual improvements in design and production processes. (as did changes to pad design etc ) Again, I'm not bashing the product, simply stating a reality regarding the SDS7.
Anyway, found my issue, need to cut one track and add a short wire. Not happy doing this sort of thing but it's either do that or get a new run of 50 boards done. The way PCB manufacturers price boards, it's not economical on a small run of boards like this to do proto's and samples. Yes if you order a few hundred and up they will generally supply production samples to test.
Somehow during the PCB layout, I managed to cross link a track. Have modified the proto unit's PCB and it's working a treat.
--- In Simmons_Drums@yahoogroups.com, "philmurr" <philmurr@...> wrote:
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> A schoolboy error :-(
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> I think there are many reasons for errors on schematics:-
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> 1) As a company they were very experimental, and didn't always follow best practice updating documents (how many of them that you've seen have hand-drawn/unreadable changes on them?)
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> 2) Some of the schematics that are out there have come from various sources, and there's nothing to say that they're the most up to date ones, or ones that match the hardware we have. Even the SDS3 schematics are full of errors, and that's a very simple circuit !
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> 3) As you say, most bits of Simmons kit have wire / component mods (for example I've an internal service note that says the latest pcb design for the SDE has a chip laid out backwards, that meant they had to make a piggy-back board to make it work !). These guys weren't using foolproof CAD tools to design the stuff !
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> It makes it a little more of a "challenge" to get stuff working again. I don't think there was anyone genuinely incompetent or out to ruin his business. It's just one of the problems you get when you leave Engineers in charge of products (and that's not meant to be rude about Engineers, after all, I'm one...)
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> Good luck with the memory cart, at least it will look like a genuine Simmons product with all its mods :-)