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SAMS and Midi boutique decoders

Building organ consoles for use with Hauptwerk, adding MIDI to existing consoles, obtaining parts, ...
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Citroenboi

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SAMS and Midi boutique decoders

PostFri Dec 11, 2020 11:22 am

Hi all

I have about 120 1930's Compton SAM units with double touch self cancelling. When I last spoke to Midi boutique they recommended 2x mddp128uN/dp128N decoder boards.
My question is: From looking at the circuit diagram these boards deal with the switching side of things in terms of pushing a piston the tab moves (activating either solenoid). I cant work out how the board or Hauptwerk would know if I put a tab down manually.

Does anybody know if either I'm missing something obvious or if I need another type of board to accept manual switching inputs a bit like I already have for the manuals/pistons/pedals etc?

Thanks Mark
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larason2

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Re: SAMS and Midi boutique decoders

PostFri Dec 11, 2020 12:14 pm

The decoders have a midi in and a midi out. Both need to be connected for the system to work, and you need an appropriate Midi adapter to provide midi in. Hauptwerk sends the appropriate messages via midi Out on the computer, Midi into the board, whenever it makes changes. Also note that if you’re driving Sam’s, you will need the darlington transistor boards and at least one power supply to drive the Sam’s.
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engrssc

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Re: SAMS and Midi boutique decoders

PostFri Dec 11, 2020 1:22 pm

larason2 wrote: darlington transistor boards and at least one LARGE power supply to drive the Sam’s.


Based on the current draw the combined SAM's. As well appropriate large enough gauge wiring.

Rgds,
Ed
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dcaton

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Re: SAMS and Midi boutique decoders

PostFri Dec 11, 2020 2:36 pm

engrssc wrote:
larason2 wrote: darlington transistor boards and at least one LARGE power supply to drive the Sam’s.


Based on the current draw the combined SAM's. As well appropriate large enough gauge wiring.

Rgds,
Ed


And fuses. Make sure you use fuses!

The console I'm still converting has 180 drawknobs and coupler tabs, and is powered by two Astron RS-50 power supplies wired in parallel for a total peak output of 100 amps DC. I don't know who built the console, it was either Schantz or Bunn-Minnick, but someone in their infinite wisdom wired everything up to those two power supplies with not a single fuse anywhere in the entire console. And the supply wires to the magnets are extremely close to the signaling wires.

Worse, the only thing protecting the console was an old 60 amp fusible switch in the blower room, which fed a set of #12.wires that went to the console.

It's really a miracle that this setup worked for almost 60 years. A short circuit in either the ac or dc side of the console would likely have had catastrophic results.
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larason2

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Re: SAMS and Midi boutique decoders

PostFri Dec 11, 2020 3:47 pm

Ah yes, that’s true. A power supply or power supplies powerful enough to drive so many Sams would definitely draw enough current to be harmful, and if shorted out could start your console on fire. Definitely a time to get some expert help if you don’t have the appropriate knowledge and experience!
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engrssc

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Re: SAMS and Midi boutique decoders

PostFri Dec 11, 2020 6:36 pm

dcaton wrote:And fuses. Make sure you use fuses!.


Very important. Even low voltage can be dangerous.

Rgds,
Ed
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jkinkennon

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Re: SAMS and Midi boutique decoders

PostSat Dec 12, 2020 9:54 am

A lot of good advice here. I believe this is the same question that I responded to on Facebook. It would be helpful to know what voltage the SAMs were intended to operate with or at least how many ohms the coils measure in order to be sure that the power supply is correctly specified. A half amp per SAM is a typical value but you might need to go a little higher. I've had good luck using a switching supply with just 25 to 30 12V SAMs, but in some ways the old brute force "boat-anchor" power supplies with large capacitors are a better choice for a load like this characterized by huge current surges when a large registration is selected or cancelled.
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engrssc

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Re: SAMS and Midi boutique decoders

PostSat Dec 12, 2020 6:35 pm

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NickNelson

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Re: SAMS and Midi boutique decoders

PostSun Dec 13, 2020 1:53 pm

The obvious way to provide for a large number of SAM's is to simply multiply the operating current of each SAM by the total number of SAMs to give the overall maximum current and provide a power supply able to satisfy this peak demand.

However, in a large installation this will require a large and expensive PSU which will be effectively idle nearly all the time.

One plausible alternative is to consider sealed lead-acid cells 'floating' on a much more modest power supply.

For example, 2V 'Cyclon' cells can be connected in series to whatever total voltage is needed and can deliver large currents for short periods. Other battery technologies might be preferable these days.

As others have observed, though, low-voltage high-current installations have scope for causing all sorts of mischief
if things go wrong, and I'd certainly caution anyone to seek professional (or at least demonstrably well-informed) advice
unless they really know what they're doing.

Nick

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