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Ahlborn SL-250 VPO conversion project

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

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Ahlborn SL-250 VPO conversion project

PostThu Apr 29, 2021 11:11 pm

I have recently purchased an Alhborn SL-250 advertised as "not working". My intention is to either resurrect it or convert it to a VPO.

I bought it as a home practice instrument for my 10 year old goddaughter who is being taught organ on a larger A-G model in a local chapel. (She's a pretty accomplished pianist already and has taken to the organ like a duck to water. :) )

Because I already have a lot of projects on my list, my strong preference is to resurrect the SL-250 and have it out of my workshop asap.

I have researched the typical problems found in this era of A-G organs and they are among the sorts of things I have had to deal with before. So, unless I strike an insurmountable problem, such as a part that I cannot source, then I'm hoping to get the SL-250 back up and running under its own steam.

However, as mentioned, Plan B will be to convert it to VPO and, Googling around for MIDI encoders, etc, I came across Roman Sowa's nice set of modules which strike me as being the easiest and most economical way of going about a conversion.

The last thing I want to do is to solder wires to every key, pedal, stop and piston. Ideally, I want to be able to plug the organ's existing ribbon cables into purpose-built MIDI modules and connect to a computer.

But, it seems that obtaining modules is a major problem at the moment and for the foreseeable future due to COVID-related component supply problems.

So, I welcome discussion here on the suitability of Roman's modules and on any good alternatives.
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engrssc

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Re: Ahlborn SL-250 VPO conversion project

PostFri Apr 30, 2021 12:21 am

Welcome to Hauptwerk. I have only a brief understanding of this instrument and comments would only be general.

It is old which you probably already know. As in around late 1990's. There js a possible source for a manual at a cost of €28.

http://www.manuals.group/orderref0.phphttp://www.manuals.group/n_download_manual.php?brand=Ahlborn&model=sl250&doctype1=Schematics&doctype2=Diagrams&doctype3=

Most likely obtaining working repair parts for an instrument that old could be expensive esp in time to analyze if such parts could even be found.

Some basic initial questions:
Does it have MIDI connections? Probably not.
Are there any obvious external issues?
Does it turn on?
Does it make any sound?

A conversion would involve know things like which type of key contacts are used and how they are wired.

Roman does have simple to use connectors which work with his encoders, but they do involve soldering?

https://www.midi-hardware.com/index.php?section=prod_info&product=WIPLUG2&R2=USD

or these with screw terminals and use 16 pin headers.

https://www.midi-hardware.com/index.php?section=prod_info&product=WIPLUG&R2=USD

Rgds,
Ed
Last edited by engrssc on Fri Apr 30, 2021 2:03 pm, edited 1 time in total.
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GTC

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Re: Ahlborn SL-250 VPO conversion project

PostFri Apr 30, 2021 6:37 am

Yes, it's 1990's vintage and Ahlborn-Galanti support is zero. To it's credit, a former A-G service tech has elsewhere described it thus: "It was a great sounding organ in its day, and still sounds credible today with some work on it."

I do have a copy of the Service Manual. Again, my research has already uncovered the most likely points of failure and I have dealt with such issues before, so that aspect doesn't bother me too much. However, if a proprietary unobtainable chip such the CPU has failed, then it's definitely game over for Plan A, and Plan B (VPO conversion) will commence.

Does it have MIDI connections? Yes
Does it turn on? Don't yet know until I take delivery of it on May 15.
Does it make any sound? (ditto)

A conversion would involve know things like which type of key contacts are used and how they are wired. I'm not sure about the type of key contacts until I see them, but it uses matrix technology.

Yes, I very much like Roman's way of doing things. This schema is very appealing to me (albeit I have only 2 manuals):
https://www.midi-hardware.com/img/3k1p- ... op-lcd.gif

I would need to ask Roman -- or someone who has used this schema -- how compatible the SL-250 is with it.
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larason2

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Re: Ahlborn SL-250 VPO conversion project

PostFri Apr 30, 2021 11:54 am

Sometimes the Midi still works even if the organ does not, so I would check this if you’re comfortable with using the power supply in its current state. If you’re worried about the power supply, check and repair that before doing anything else with the rest of the organ.
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engrssc

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Re: Ahlborn SL-250 VPO conversion project

PostFri Apr 30, 2021 1:46 pm

Aside from possible MIDI output from the keyboards, Roman has designed these specific functions (built into) his encoders which can be activated by means of a Keypad function:

https://www.midi-hardware.com/index.php?R2=USD&section=prod_info&product=KEYPAD

4.2.20 Ahlborn Common Functions - #2146
This is specific to Ahlborn modules only. When assigned to a keyboard, the buttons act
in a way usable for group of controls in Ahlborn module called "Common Functions" like
general cancel, tutti, etc. It works very much like event 143 described in chapter
4.2.17 (below). When a key is pressed, MIDI controller 71 (47 hex) is sent with value 64-127,
and when it is released, the same MIDI controller but with value lowered by 64. To
reach different groups of controls, you may need to create splits in keyboards and
choose different ranges with transposition settings

4.2.17 Ahlborn Organs stops control - #2143
When assigned to a keyboard, each key becomes specific stop controller in Ahlborn
Organs. When a key is pressed, MIDI controller 70 (46 hex) is sent with bit 6 of the
value set, and when it is released, the same MIDI controller but with bit 6 of the value
cleared. Other bits of the value are determined by the button pressed. In another
words, pressing the button sends CC 70 with value range 0-63, and releasing a button -
CC 70 with value range 64-127. This is default way of controlling stops in Ahlborn
Organs. Lowest value adjustable by transposition.

If these functions are still operable it would resolve many issues aside from the organ being considered "not working".. Hope that helps.

Rgds,
Ed
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GTC

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Re: Ahlborn SL-250 VPO conversion project

PostFri Apr 30, 2021 8:26 pm

larason2 wrote:Sometimes the Midi still works even if the organ does not,


Yes, I guess that's a possibility.

so I would check this if you’re comfortable with using the power supply in its current state. If you’re worried about the power supply, check and repair that before doing anything else with the rest of the organ.


When diagnosing faulty equipment I always start with the power supply. Low rail voltages can be a key problem with this stuff.
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Re: Ahlborn SL-250 VPO conversion project

PostFri Apr 30, 2021 8:30 pm

engrssc wrote:Aside from possible MIDI output from the keyboards, Roman has designed these specific functions (built into) his encoders which can be activated by means of a Keypad function: [...]


Yes, I had noticed that when I was trawling his site. It's one of the reasons that I was drawn to his solutions, however, as we know, things are in a state of flux over there so, unfortunately, I can't necessarily rely on Roman as a supplier and I have to get this organ up and running -- one way or another -- asap.
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Re: Ahlborn SL-250 VPO conversion project

PostSat May 01, 2021 3:43 am

I have used Midi Boutique kits for a conversion of an old console and for additions to my current console. Typically they can supply within 10 days but you would need to check. For a whole conversion you might use one of their bundles. Have a look at https://www.midiboutique.com/MIDI-Encoders/hwce2 - their documents are quite helpful.
Best wishes
Iain
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GTC

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Re: Ahlborn SL-250 VPO conversion project

PostSat May 01, 2021 7:39 am

IainStinson wrote:I have used Midi Boutique kits for a conversion of an old console and for additions to my current console.


Thanks. Yes, plenty of functionality in that package. It is priced nicely, too. I'll definitely give consideration to that.
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Re: Ahlborn SL-250 VPO conversion project

PostSat May 01, 2021 8:51 am

Since you’re looking for inexpensive, you should check out what I have posted working with an Arduino Mega. It certainly is the cheapest way to go! I’m planning on posting code for bussed keyboards and more functionality in the near future.

https://create.arduino.cc/projecthub/La ... _&offset=6
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GTC

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Re: Ahlborn SL-250 VPO conversion project

PostSat May 01, 2021 9:43 am

larason2 wrote:Since you’re looking for inexpensive, you should check out what I have posted working with an Arduino Mega. It certainly is the cheapest way to go! I’m planning on posting code for bussed keyboards and more functionality in the near future.


That's certainly a budget solution, however I'm wanting to avoid all of that soldering. I want to take advantage of the existing 8x8 matrices as far as possible.

I'll trade reduction in labor for module cost ... up to a point.
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Andrew Grahame

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Re: Ahlborn SL-250 VPO conversion project

PostMon May 03, 2021 5:37 am

This makes me feel old! I remember when the SL-250 was a newly released model. It was quite a good instrument at a reasonable price. It had a cleverly designed versatile 2-manual stoplist which was notable for what it didn't have as much as for what it possessed - there was no waste, duplication or redundancy. Every stop had a meaningful place within its department and within the overall tonal scheme and it was possible to do a great deal with these resources. User-controlled voicing wasn't an option, though the dealer could make voicing changes to suit a permanent installation. The sound, for its day, was quite presentable despite the fact that this was one of the models in a "budget" series of instruments. A friend of mine possessed the 3-manual version - the SL-300 - and it was just as good with the added advantage of a 3rd manual department.

In the late 1990's I presented some organ-playing seminars in Sydney and regional NSW, sponsored by the local Ahlborn-Galanti dealer. For one of these events the SL-250 was the instrument he supplied for me to use and demonstrate. All of this was pre-Hauptwerk.

Fast forward to the present day, and we now find instruments of this vintage reaching the end of their "first" life, and now finding renewal with conversion to Hauptwerk. This is a very fitting way for a decent specimen of its day to move forward in support of another generation of organists.
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Re: Ahlborn SL-250 VPO conversion project

PostMon May 03, 2021 7:05 am

Thanks Andrew. I've had a few people elsewhere tell me that the SL-250 was good value for the money back in the day.

As per my OP, I will first try to resurrect the SL-250 but, until it arrives at my workshop, I am expecting to find anything from a blown fuse to the charred remnants of a lightning strike. A rotted out CPU board battery is probably odds-on.

One way or another it will sing again. :-)

Out of interest, who was the local A-G dealer back in the day? Truth be told, I wasn't even aware of the A-G brand until goddaughter began lessons.
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Andrew Grahame

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Re: Ahlborn SL-250 VPO conversion project

PostMon May 03, 2021 7:54 am

David Pitts was the A-G agent for Australia and New Zealand, operating under the company name “Pipeless Pipe Organs”. Ian Sell did the loudspeaker/amplifier work on the installations. These days David is retired, and Ian now operates as “Virtual Pipe Organs Australia” - building splendid new Hauptwerk-based consoles and repurposing old organ consoles as Hauptwerk instruments. Ian converted my old Miller Norwich organ console to become a fine Hauptwerk instrument for a country church, and he also built the 4-manual keyboard stack for my own Hauptwerk organ.
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Re: Ahlborn SL-250 VPO conversion project

PostMon May 03, 2021 8:29 pm

Andrew Grahame wrote:converted my old Miller Norwich organ console to become a fine Hauptwerk instrument for a country church, and he also built the 4-manual keyboard stack for my own Hauptwerk organ.


Do you happen to know what MIDI technology was used? Proprietary, or from one of the various well known MIDI module suppliers?
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