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Orban 111b Limiter Module
Old 27th May 2020
Orban 111b Limiter Module

Hello fellow geekslutz,

I’ve been a big fan of these Orban 111b spring reverbs first quite a while. At one time, I shot my first 111b out against my EMT 140 and, to me, the plate came second so I sold it. Since then, I have at least 5 friends who have bought one just because they loved using mine.

Anyway, I’ve found that these lovely spring reverbs suffer a common problem where their unique potted limiter module fails. I have contacted Orban and they have told me that the documentation is long gone. I’m now on a hunt to re-create this small circuit board for the good of all 111b owners out there.

So, the question is, how do I figure this module out.

1) find somebody who has already done it - At one point early on, I saw a picture of a 111b with a circuit board in place of the limiter module but the owner did not answer my email.

2) find somebody who worked at orban when this was made

3) remove the potting to reverse engineer - I have tried some testing on an eq module (which does not need reverse engineering) by heating it up with boiling water. I didn’t find this method safe enough to do without destroying the components. Other options could be to find a corrosive de-potting chemical, but I would need to find one that would keep the board intact.

4) X-ray - use a company that x-rays circuit boards. Probably the most expensive option, but at least I would have a board layout and general component list.

5) Try to figure it out from testing? This one is the hardest and probably the last resort.

Whew! Well, I have resources to design and manufacture some of these, but no way to get any information on it’s unique transient-limiting design. If anybody has any information or knows somebody that can help, it would be much appreciated!

Thanks so much!
Attached Thumbnails
Orban 111b Limiter Module-9f91e80c-fab3-47e2-abde-7ab3fa4d6d70.jpg   Orban 111b Limiter Module-60983656-aa22-4e4b-a517-aef7e33e8cfe.jpeg  
Old 27th May 2020
Take a look here.
There are companies who will "de-pot" modules as well.
We successfully did this to a CBS limiter because it was malfunctioning and the module was no longer available from CBS.
Once you have the module de-potted it would be a fairly simple procedure for any good technician to back engineer the components and make a schematic.
I have a device in house right now where all the ICs have had their identification removed by sanding. Not fun! In all cases you should check with the manufacture, as you have done, to insure this is the only way to repair the unit. There are copyright and other legal matters to any discoveries you make so I would not share this with others unless you have written authorization from the manufacture. FWIW Best of luck!

ps I sometimes feel like I am a CSI trying to figure out a crime when all the finger prints have been removed.
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