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Just starting a conversion - advice requested

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Just starting a conversion - advice requested

Postby RaymondList » Sun Mar 11, 2018 4:09 pm

Hello All,

I've just gutted my 50 year-old Allen to begin work on installing Hauptwerk, and am excited to begin. This organ was an early transistor instrument with the silver wire and "wiper arm" contact system. It was suffering greatly from contact 'stutter' and failure to play a random stop on a note-by-note basis. I was wondering about other's experiences with using these contacts, but with higher voltages. I'm quite sure the original was a +5 volt keying, so it was quite low. I'd like to use Midi Boutique HWCE2 with the existing contacts. Anyone have an opinion as to my possible success? Thanks much in advance.

Ray
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Re: Just starting a conversion - advice requested

Postby engrssc » Sun Mar 11, 2018 9:36 pm

You could use a higher voltage (within reason) and drop the voltage via resistors (need to do it for each contact)
to the specified input voltage of the encoder. Like 2 resistors in series with the take off between them maybe.

Rgds,
Ed
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Re: Just starting a conversion - advice requested

Postby jkinkennon » Mon Mar 12, 2018 1:48 pm

I've added MIDI to a number of consoles though none of the Allens I've done had the contacts you describe. It has been my experience that once cleaned, contacts will stay reliable if you avoid going back to the older voltages that were high enough to cause arcing. I've seen more carbon buildup issues than problems with tarnishing in other words. Clean contacts should be stable for a long, long time at 3.3V or 5V. At least that's my observation. I've burnished the open leaf contacts on several Allens and have not had to repeat the process.
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Re: Just starting a conversion - advice requested

Postby RaymondList » Mon Mar 12, 2018 5:40 pm

engrssc wrote:You could use a higher voltage (within reason) and drop the voltage via resistors (need to do it for each contact)
to the specified input voltage of the encoder. Like 2 resistors in series with the take off between them maybe.

Rgds,
Ed


I was thinking along those same lines. Thanks for the input.

Ray
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Re: Just starting a conversion - advice requested

Postby RaymondList » Mon Mar 12, 2018 5:53 pm

jkinkennon wrote:I've added MIDI to a number of consoles though none of the Allens I've done had the contacts you describe. It has been my experience that once cleaned, contacts will stay reliable if you avoid going back to the older voltages that were high enough to cause arcing. I've seen more carbon buildup issues than problems with tarnishing in other words. Clean contacts should be stable for a long, long time at 3.3V or 5V. At least that's my observation. I've burnished the open leaf contacts on several Allens and have not had to repeat the process.


Thanks for the reply. I'm surprised you've never encountered key contacts like these. It's like a miniature telephone pole farm, but of stiff silver plated wires. Relays pull plastic strips to the side about 1/4 inch as stops are activated and those strips pull the wire contacts closer to the keying wipers so they swipe up the wire as the keys are pressed. Hundreds of contacts. You must have done all newer Allens. This organ was not an older 'tube' type Allen (they used the same contact system but with much higher voltages), but is an early transistor model. I can't remember if the keying was 5 or 12 volts, but it was not greater than that and thus has had no arcing. I think it is more of a tarnishing of the silver (or the wearing-away of the plating) that causes the issue. Many years ago I worked for Gillette Organ Service in NJ and we were forever cleaning these contacts. Did organs at least once a year. Maybe it was more of a sensitivity of the keying circuits that caused the issues. Again, thanks for the input!

Ray
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Re: Just starting a conversion - advice requested

Postby jkinkennon » Mon Mar 12, 2018 8:52 pm

Yes, pipe organs would be at least 12v not to mention coils which are magnetic and encourage an arc when a contact is opened. I see carbon deposits on the little keyboards used for chimes but don't normally get a look at pipe organ keyboards.

The Allen digitals from MOS-1 through ADC tended to use the open leaf contacts. I've seen what you describe, more or less, but thought it was on a Rodgers analog, maybe a 32B -- perhaps I'm wrong. That one had tons of magnet wire running from the keyboards. It did shift little rails using coils. Let's see, the Allens I've done were mostly a couple of 603-Ds, a 675-TH, the original little MOS-1 digital, and similar. This might have been a really old Allen. Too many consoles have come and gone.

No matter, try going with a good set of contacts, or if you have multiple contacts for a note parallel them -- that's my plan for the "magnet wire" manuals if I don't toss them and substitute something better. At one point I picked up a bunch of phosphor bronze wire from a model train supply house with the intent of rolling my own contacts. I'm resistant to the expense of electronic sensors.
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Re: Just starting a conversion - advice requested

Postby RaymondList » Mon Mar 12, 2018 9:41 pm

As I mentioned, I used to do a little work on these things in the 1970's+, and I don't think Rodgers ever used keying like this. Allen used it for their tube organs and kept using it for the early transistor organs - - pre digital. This thing had two and a half huge chassis of discrete transistor generators (about 110 tone generators in each chassis), and yes, there is about 450 pounds of magnet wire connecting the key contacts to the generators. You did get me thinking about this though. I have something like 10 contacts for each key. I don't want to spread the available power around too much, but perhaps if I wire it up with two contacts per key, it would key the MIDI smoothly. I'll have to call a friend of mine who is an electrical engineer to see what he thinks about that. I'm sure he'll have an opinion, but perhaps too deep for what information I need!! Thanks a lot for this discussion!
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Re: Just starting a conversion - advice requested

Postby engrssc » Tue Mar 13, 2018 1:40 am

Redundant (multiple, parallel connected contacts per note) can only add to the reliability factor. As long as they are available, why not use them?

Rgds,
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Re: Just starting a conversion - advice requested

Postby RaymondList » Tue Mar 13, 2018 11:19 am

I'm not sure. I think a single contact has a better chance of keeping itself 'clean' with a microscopic spark during contact. I think of those tarnished contacts as miniature resistors distributing current through the multiple contacts in variable amounts. I'm going to talk to my friend who is an electrical engineer with 45 years experience designing switches of all types. (He holds 23 patents!). I know we have talked about his work for auto companies when they were just getting started with digital. He said they had a terrible time understanding what could build up between the contacts of plugs and switches, so he might be the perfect person to discuss this matter with. I'll update with what I find out from him. He is away right now, but I'll get with him soon.
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Re: Just starting a conversion - advice requested

Postby organsRgreat » Tue Mar 13, 2018 3:46 pm

Slightly off-topic, but I'm amazed that all the contacts on my Casio VZ1 synths are still working. The model was released in 1988, so mine are around 28 years old. I use three of them as controller keyboards for Hauptwerk. Do these contacts just keep going, or should I expect trouble soon?
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Re: Just starting a conversion - advice requested

Postby RaymondList » Tue Mar 13, 2018 8:43 pm

RaymondList wrote:I'm not sure. I think a single contact has a better chance of keeping itself 'clean' with a microscopic spark during contact. I think of those tarnished contacts as miniature resistors distributing current through the multiple contacts in variable amounts. I'm going to talk to my friend who is an electrical engineer with 45 years experience designing switches of all types. (He holds 23 patents!). I know we have talked about his work for auto companies when they were just getting started with digital. He said they had a terrible time understanding what could build up between the contacts of plugs and switches, so he might be the perfect person to discuss this matter with. I'll update with what I find out from him. He is away right now, but I'll get with him soon.


I'm replying to myself here, but want to update in case someone else was following this. I asked which was better, 1 or more than 1 contact per key. Here is his response:

"Parallel contacts will not drop voltage, they divide current but thats a positive thing. Its called bifurcation and is always done on critical circuits."

So, I have 12 contacts per key available. Now I just need to decide how many I should take the time and effort to use! It would take a LOT of work to use all 12. Maybe three or four would be a good number.
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Re: Just starting a conversion - advice requested

Postby engrssc » Tue Mar 13, 2018 9:15 pm

Generally 2 is considered adequate.

Rgds,
Ed
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Re: Just starting a conversion - advice requested

Postby TheOrganDoc » Tue Mar 13, 2018 9:51 pm

After working on both Pipe and Electronic Organs for over 60 years, I utilized the original contact blocks (7) with 4 contacts shorted together for keying and the other 3 connected to Common, with the original silver shorting bars, and after cleaning all Sterling Silver contact surfaces my organ played very well for about two years, then I started having dead and intermittent keys. For another two years I used Deoxit D5 on the troublesome contacts using the extension spray tube. This worked well for a while and then other notes went missing. I decided to do something. :roll:
I checked out several methods, I had had problems in the past with magnetic switching, that has been used on many modern organs, so I decided to order a few Optical switch devices, after much testing I decided to build a batch of 12 note circuit boards, with these Opto-Switches, After wiring them to my midi encoders and adjusting them, I have now been using them for the past eight years with not even one problem. When you first play using Optos, you will actually feel the positivity when playing !

I have a few photos of my system that I will send to you if you DM me your Email address, and feel free to ask me any questions !
There are also devices known as "Hall Effect Devices", with care in installing them, and their small associated Magnets will work reliably also. I intend soon to experiment with them if they are not to expensive ! Mel
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