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Need help with SAMs

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

Need help with SAMs

Postby Andrew_Melbourne » Sun Oct 01, 2017 5:25 am

I have been gradually building up my 3/4 manual Hauptwerk system for about 4 years now, using midi-hardware.com equipment for the MIDI and SAM control systems. I have bought two sets of SAMs via ebay. The first set, of about 40 from the UK, are old Kimber-Allens and I have recently made great progress in sorting out the required electronics, with a lot of help and advice from Roman Sowa of midi-hardware.com. They are essentially ready to be mounted and used.

The second set came from the USA: 53 SAMs in superb condition on one rail that had to be cut in two for shipping but with the very extensive wiring all still intact. I don’t know what make they are. They are labeled “T&B-1”, so possibly Taylor & Boody. I have been trying to understand all the wiring and I have been successful with the reed switch side of things. However, the high-current electromagnet side is not so simple. While I have managed to actuate some of the tabs using my 12V supply, I haven’t been able to do this in a consistent way, or to figure out which connections do what.

Each SAM has two very thin long wires coming out of it, which I suspect is for some sort of control system that switches the common high-current supply to the magnets when they receive a logic signal. (There is definitely a working common earth connection for all SAMs, and I think also a common positive.) I think that this might work with my MIDECO decoder, and I have obtained some flickering tab responses in my testing, but I don’t really know what I’m doing. If this is what those two thin long wires are for, it would be great to avoid having to install a thick positive high-current wire to each SAM from my MIBO current booster board that can fit on the MIDECO.

I am hoping that someone can identify the SAMs in the attached photos and give me advice on the wiring options. My project is pretty much stalled now and has been for months as I don’t know how to proceed. I could just go ahead with the 40 Kimber-Allens, but the US SAMs are in such great condition it would be a shame not to use them too (they weren’t cheap either!). I already have the MIDI equipment to read and operate up to 64 SAMs.

thanks
Andrew
(I lived in London until last year, and am now living in Melbourne)

Image embedding from Google Drive unfortunately didn't work, so here are direct links that you will have to follow.

https://drive.google.com/open?id=0BwtUs6wYhB3dUmx0YWllTkRMODg
https://drive.google.com/open?id=0BwtUs6wYhB3dSVdkc2VwUEVBM3c
https://drive.google.com/open?id=0BwtUs6wYhB3dUWNIcF9hWnRCelU
https://drive.google.com/open?id=0BwtUs6wYhB3dLW5xWG5Mb2NraXM
Last edited by Andrew_Melbourne on Sun Oct 01, 2017 5:56 am, edited 1 time in total.
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Re: Need help with SAMs

Postby engrssc » Sun Oct 01, 2017 5:51 am

Unfortunately, the images did not show up.

Rgds,
Ed
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Re: Need help with SAMs

Postby Andrew_Melbourne » Sun Oct 01, 2017 5:59 am

Thanks, Ed.

Yeah, Martin Dyde has kindly been helping me with this tonight, though in the end it seems that Google Drive-hosted images aren't suitable. I have edited my message to post URLs rather than embedded images, as suggested by Martin. At least these are high-resolution versions, rather than the 640-pixel-width versions that I had prepared for embedding purposes.

Andrew
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Re: Need help with SAMs

Postby NickNelson » Sun Oct 01, 2017 6:58 am

Hi Andrew,

I broadly agree with your analysis. It seems clear that the transistors on each board are to switch the respective coils on in response to signals on the thin green wires. The topology and resistor values are a bit odd though, as the two drive circuits don't seem to be symmetrical. It would be helpful to know if there are any numbers on the transistors. If so, can you let us know? Working out the polarity and drive characteristics
will depend on whether they are NPN or PNP transistors (and they might possibly be Darlingtons as well).

Nick
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Re: Need help with SAMs

Postby adrianw » Sun Oct 01, 2017 9:21 am

It is a bit weird. From inspection and intuition I think the circuit is this (except the 150R is actually 560R):

Image

If the CR3 component is indeed an 18V zener (pure guesswork since the colour code is not clear) it is perhaps a 24V circuit so operation might be marginal at 12V. (Edit - it is just as likely that it is 8.1V and it is a 12V cct).

Problem is that if this circuit is continuously powered one or other of the coils is always on. This seems unlikely to be what the designer intended or you want, so it looks as though one of them should be strobed when a change is required and the green wire determines whether the tab will then be powered up or down. Sort of thing that works better with mechanical combination setters than digital electronics!

I would ignore the electronics. Use the Orange as a common +ve, leave brown unconnected and run an MIBO wire to the other side of each coil directly. You can ignore the electronics - no need to remove it - it is not going to cause any problems and the snubber diodes are useful. Worth experimenting for one of them anyway to see if you have enough voltage to operate the coils reliably.
Last edited by adrianw on Sun Oct 01, 2017 10:13 am, edited 1 time in total.
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Re: Need help with SAMs

Postby rhedgebeth » Sun Oct 01, 2017 9:50 am

For whatever help it might be the basic units are by Reisner/Organ Supply Industries, but are a stripped down non-stock version. The control circuits appear to be presumably by Allen, though I haven't seen this particular variant. I'm guessing 80's vintage. The Allen attribution is based on the tab engraving. Allen did use these units. We're currently doing a conversion of a 70's Allen which uses a nearly stock version of the units. The units are still in production by OSI (still with mechanical contacts, but current production has isolated common of the coils, unlike early versions of these.)

Without trying to analyze the circuitry too precisely I'm assuming that the diodes are 1N400x devices for flyback protection of the drivers. Two driver circuits for two coils. The second reed switch was probably an isolated status read for the combination action (speculation).
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Re: Need help with SAMs

Postby rhedgebeth » Sun Oct 01, 2017 10:15 am

I think Adrian W may have hit the mark and that it may have been designed for a setterboard implementation. Probably not for 24v however, 12v more likely, though I believe Allen used as much as 48v for a time (no longer allowed by code, incidentally). Measuring the coil resistance should tell the story. I would expect to find 30 ohms for 12v operation.
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Re: Need help with SAMs

Postby adrianw » Sun Oct 01, 2017 10:23 am

Yes, the 24V was based on the colour coding of the zener apparently being brown (1) and grey (8). I guessed 18V (which would only work on 22V+) but on reflection it could as well be 8.1V which would be right for 12V.

- Adrian.
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Re: Need help with SAMs

Postby jkinkennon » Sun Oct 01, 2017 4:40 pm

I'd agree about these being from an Allen, something perhaps a bit more recent than the 80's just based on the fact that the tabs look a bit more recent than what I've seem on MOS-2 organs.

Allen used a switched power supply, in fact the third photo shows the blue, green, red, and white wires as I'd expect to find them on a terminal strip. These four wires would switch power to one division at a time which allowed a smaller current rating for the supply.

Referring to Adrian's sketched schematic the green wire is driven high or low by TTL circuitry through a 1.0 to 2.2k resistor. That enables one darlington transistor or the other. Then the orange wire (color coded by division) is pulsed high for about 50 ms or so.

In the MOS-2 days the voltage used was nominally 48V and these are likely the same though they might have been operated at 24V -- not sure. The only switching supplies I've seen were about 48V for tab style SAMs and around 52V for drawknobs!

Let me know what else I can suggest. It's easy to do the decoders except that some extra GPIO pins have to be used to pulse the power supply. Without an Allen supply the interface would be a bit of a challenge.

EDIT: If an Allen supply can be located then the GPIO pins for the blue, green, red, and white wires would be set to open collector and the wires get pulled to ground for about 50ms.
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Re: Need help with SAMs

Postby rhedgebeth » Sun Oct 01, 2017 6:09 pm

Aha! Always helps to have been there. Thank you jkinkinnon for your very definitive analysis. This also answers, at least in part, a question I've had re: Allen practice as to what timeline the 48v operation was in use.
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Re: Need help with SAMs

Postby jkinkennon » Mon Oct 02, 2017 5:24 am

I might add that I had an Allen ADC model that used the 48V power. That's the latest vintage that I'm sure of. There were four similar outputs on the capture supply plus a 5th CP (coupler panel?) section that would activate when two inputs were pulsed. Not sure I understand why they did that. So a single power supply could handle a 3 manual console, pedals stops, and a coupler rail. I think some of the theater organs and perhaps the largest classical consoles used a pair of these supplies.

For safety each supply section could charge a capacitor that fed a circuit which would switch off the power supply by tripping the switch that looks more like a circuit breaker. That way is a failure caused an output to stay powered then all the power would get switched off. Because the decoders only need to output TTL levels it made it easy to implement. My matrix encoders are actually encoder/decoder combinations for older Allen consoles. The project info is on my web site and I can offer a little assistance if anyone wants to try them out or built their own versions to sell. I retrofit a few consoles but I'm not ready to go back into a real business as I'm happily retired.
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Re: Need help with SAMs

Postby Eric Sagmuller » Mon Oct 02, 2017 6:39 am

I had an MDS Allen back in the 90's. Whenever I would make a combination change the chandelier above our table would blink, it was on the same circuit. I always thought this was kind of drastic.

Later on I went all pipes and had electric SAMS on the console. I installed a HD supply using a large filter cap. Never any disturbance with this setup. Only bad part is there was no protection for the SAMS should a driver fail or stay on.

Eric
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Re: Need help with SAMs

Postby Andrew_Melbourne » Thu Oct 12, 2017 5:17 am

Thank you so much, everyone, for your generous advice. Apologies for the delay in acknowledging - I have not had any time in recent days to devote to my organ project.

Some of the information is a bit too advanced for my current level of knowledge. I had another go at touching the 12V power supply to various parts of one of the SAMs. Sometimes one or two SAMs in the group do go down, but mostly it is just some flickering motion. I hope that these don't need more than !2V, as I have managed to source three affordable 30A 12V supplies, and I'm not sure that I could the same for high-current supplies at higher voltages.

My attempts to use a multimeter to measure the resistance of the coils suggests that they are about 40 ohms.

I think the next thing to try is to separate one of the SAMs completely from all the others, so that I don't have the confounding from the others in the group.

Andrew
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Re: Need help with SAMs

Postby Eric Sagmuller » Thu Oct 12, 2017 12:30 pm

Reisner SAMS run about 30 ohms for 12V units. The Petersen units run 21 ohms for 12V and 42 ohms for 24V.

As far as high current supplies go, you shouldn't need a tremendous amount of current if using a large enough filter capacitor. That stores the "pulse" energy needed to move the tabs.

Eric
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Re: Need help with SAMs

Postby adrianw » Thu Oct 12, 2017 2:29 pm

I am afraid I still think you most likely have 24V devices, not 12V. (And likely not 48V either - the resistor values are wrong for that).

To test, just connect Orange to 12V, Green and Brown to ground momentarily. It should pull down smartly. If if just flicks, operation on 12V is just not going to be possible.

- Adrian.
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