The Organ Forum

HI.  I need a little help here.  I recently acquired a butchered Leslie 204 cabinet I will slowly be bringing back to life and hooking up to my Gulbransen D.  I have a problem with the rotosonic spindle in the lower (tibia) drum.  The contact wire in the shaft where the Mercotac goes is broken (when the unit was butchered for the Mercotacs and amp, I guess it was snapped off).  I ordered some  Mercotac connectors and the receptacles (with the pin and speaker wire) directly from the Mercotac company.  But, the receptacles are designed to fit INTO the shaft.  From what I can gather, the existing receptacle with the broken wire was designed to fit OVER the spindle shaft. 

Has anyone here attempted to replace broken rotosonic/Mercotac receptacle wires?  How would you recommend that I remove the existing receptacle without messing up the spindle?   Is is possible to leave the existing receptacle intact and just replace the pin/wire assembly?  Apparently some repair shops have just the pin/wire assembly, but I cannot find that for sale anywhere.  Any help or advise would be greatly appreciated.  I do have a almost identical "back-up" spindle and drum from a 100GK (speaker/drum connectors are male in one and female in the other) but I would prefer to "save" the drum/spindle that came with the cabinet.

- jim

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Jimmy Williams
Gulbransen Model D, Leslie 204, hobby organist/technician

Hi Jim,

All the Mercotacs that I've seen use press fit receptacles that are inserted in the shaft.  I'm having a bit of difficulty visualizing one that would fit over the shaft.  Does it appear to be a second aluminum piece that's pressed over the drum shaft that accepts the receptacle or ??  At any rate, I've had to machine a number of repair parts for my Leslie speakers.  I'd be more than happy to fit the replacement Mercotac receptacle to the shaft if you want to send me the shaft and the receptacle.  The easiest way out might be to make a small aluminum turning that would press over the drum shaft and be sized to accept the Mercotac receptacle but I couldn't advise you unless I saw either the parts or a close up picture.  Besides my organ hobby I also like to spend time in my garage machine shop -- another hobby that almost takes up as much space as these organs.

Send me an email if you're interested in some free service for a fellow Gulbransen fan :^)

 

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Gary
(Rodgers 321B, Gulbransen Theatrum, Hammond H-133, Gulbransen Rialto K with 100GK Isomonic Leslie, Rodgers 322 Trio Deluxe,Rialto K 1135 with 102 and 103 Leslie, Allen Theatre Deluxe with Gyrophonics and other speakers.

Hi Gary!  Nice to hear from you again.  Here's the story.  I've seen several types of receptacles used on the old rotosonic spindles. 

(a) The one I am most familiar wth - the spindle is one metal piece and the receptacle is just a pin and some sort of plastic-type material that fits into the shaft.  A single wire is connected to the pin and threads through the shaft, into the speaker/drum.  The spindle on the 100GK cabinets I worked on appears to be like that.  In other words, the receptacle piece itself is not encased in any sort of metal cylinder.  I cannot find that sort of "bare-bones" pin/wire receptacle for sale anywhere.  Dave's Electronics reportedly has them on hand to repair rotosonic spindles though.

(b) The spindle that came with my 204 cabinet appears different.  In this case, it looks like the receptacle was "added on" to the existing shaft.  The pin/wire assembly is inside a metal cylinder, and this cylinder appears to be mounted OVER the shaft.  In other words, the shaft fits INTO the receptacle from the bottom of the receptacle.  The wire threads through the shaft just like (a),   I'll try to send a photo if it will help - don't have the camera handy right now.  This is the one I have where the pin is broken. 

(c) The new ones.  The cheapest parts suppier for Mercotac equipment the manufacturer itself.  Many commercial parts suppliers can no longer sell the Mercotac because of mercury issues.  Anyway, Mercotac direct-sells the slip rings as well as the connector caps and the receptacles.  They are all listed in the catalog under Model 205.  You can look at them here: http://www.mercotac.com/html/205.html .  I ordered some Mercotacs as well as the connector caps and the receptacles.  These new receptacles are enclosed in metal cylinders that are designed to be press-fit INTO the rotating member.  The most "compatible" receptacle to what is used in the rotosonic spindles for the 100GK and the 204 is number 591.  

So, my main question was - how do I remove a receptable style "b" from the shaft, so I can replace it with a style (c)?  Any ideas?  Or do you think it is welded together or otherwise mounted permanantly?

I'll PM you too about some other things.

Take care,

jim

 

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Jimmy Williams
Gulbransen Model D, Leslie 204, hobby organist/technician

Hi Jim,

I'm getting a better "picture" but if you do get a chance to take a picture that would be great.  Does it look like they pressed the style "b" over the shaft so you might have the opportunity to muscle it off with some twisting and pulling?  One clue that it's two pieces could be the difference in the metals.  As I recall most of the shafts I'd worked with are just plain aluminum rod, maybe the "b" receptical is different and it could be separated?  Are you thinking that if you pull it off you would be able to press fit the type "a" into the Rotosonic shaft perhaps with a bit of drilling?  If I've got the right mental picture would the dimensions be such that you would be able to drill out the "b" receptical and press in the "a"?  If you were taking that approach I'd recommend using a metal lathe for drilling/boring in order to do a nice straight and concentric job.

If the opening in the "b" receptical is too large for a press fit over the "a" then a small sleeve could be machined and pressed into the "b" receptical in order to give a nice press fit to "a".  If that would work it would be a pretty clean and simple fix. 

Of course if you wanted to try and stay as "stock" as possible (and I'm visualizing your part correctly) one could drill out the broken pin/insulator from the receptacle, turn a small piece of delrin rod to press into the hole and finish up by drilling a small hole in that delrin rod insulator for a replacement pin that could be pressed in.

Do any of those sound like they would be practical based on the dimensions of your parts?  You've got me interested so the offer still stands :^)

I'm shooting in the dark a bit since I've never seen a setup like this and don't have any idea of the dimensions or construction of the "b" setup.  Hopefully you can add some clarification which if any suggestions would work based on your part.

 

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Gary
(Rodgers 321B, Gulbransen Theatrum, Hammond H-133, Gulbransen Rialto K with 100GK Isomonic Leslie, Rodgers 322 Trio Deluxe,Rialto K 1135 with 102 and 103 Leslie, Allen Theatre Deluxe with Gyrophonics and other speakers.

Gary, here are two photos for comparison.  The first is what I call the "a" type (100GK spindle).  The second is what I call the "b" type (204 spindle).   As I said before, I can't find the pin/wire assembly for the "a" type anywhere; if I could, I would probably do like you said and drill the old one out and press a new one in.  As it stands now I can try to pop off the "b" type receptacle and see if a "c" type will fit into the spindle.  ANy ideas?  Thanks!

 

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Jimmy Williams
Gulbransen Model D, Leslie 204, hobby organist/technician

Hi Jimmy,

Sorry to take so long to respond, it was one of those weeks where all the non-organ work just buried me. It does look like they might have pressed that old style receptacle over a turned down portion of the shaft.  If that's the case you should be able to pull it off without damaging the shaft.  Hopefully they didn't put any type of locking compound (Loctite) to secure it but those bonds can usually be broken with a little heat or a bit more force.

If I'm gauging the dimensions correctly from the photos it looks like it's going to be a really tight fit to get the new style receptacle into the shaft.   If it's that close there might not be enough of the shaft left after you open up a large enough hole to press fit the new receptacle.  In that case I'd lean back towards my suggestion of making a short piece of slightly larger diameter aluminum rod that could be pressed over the shaft that had a hole sized to press fit the new receptacle into.  If it's like most Leslie that I've seen there is usually enough room above the shaft so it could be an inch or so longer and not cause any clearance problems.

I could make something up to press fit the new receptacle into but without very accurate measurements of the shaft it would be tough to make something up to fit properly over the shaft.  Offer still stands if you want me to make something up after getting the parts out here to my garage.

My thoughts on replacing the actual pin and insulator were to either yank the remains of the pin and press a new one into the existing insulator or drill out the complete insulator and then pop in a new one that was fabricated from scratch.  Nope, never done exactly that on a Leslie but I have done similar fixes on other devices.  Not sure if that's a practical fix on this one without seeing it but the "adapter" fix described above would be a sure thing.

 

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Gary
(Rodgers 321B, Gulbransen Theatrum, Hammond H-133, Gulbransen Rialto K with 100GK Isomonic Leslie, Rodgers 322 Trio Deluxe,Rialto K 1135 with 102 and 103 Leslie, Allen Theatre Deluxe with Gyrophonics and other speakers.

Thanks Gary.

The other thing I don't understand about the spindle that came with the 204 rotor is that the aluminum shaft is already longer than necessary.  For instance, I replaced the drum/spindle with the set from the 100GK cabinet - that fit into the 204 cabinet just fine.  Makes me wonder whether this drum/spindle was really native to this cabinet or not... anyway, both the drum and spindle that came with the 204 cabinet are now removed (due to gender differences in speaker connections, I could not just replace the spindle).  The 6x9 speaker in the 204 drum was also rotted out in a spot, so just as well.  I would still like to restore this just to learn how to do it, and also either to have a spare drum/spindle, or to maybe rebuild that extra 100GK cabinet in my spare time when parts come along.  I do wish there was a way to just replace the pin and insulator (which was what some others suggested as well), or even just to get a new pin in there somehow.   I do see what you are saying about machining a new part to (1) fit over the existing spindle, and (2) have a large enough diameter to press the new style Mercotac-manufactured receptable in.  This is starting to making sense - bear with me as I am not a machinist   I did write to Mercotac about this too but have heard nothing back.

I'll be in touch via PM or e-mail to pursue this further.  Thanks so much for all your help! 

This 204 cabinet project will be interesting.  I got all the motors and belts hooked up - so far so good with teh motors working and belt tension.  I have a choice now of either the 100GK amp (would require some rewiring) or a solid state quad amp - still looking into whether all 4 channels can remain discrete.  Either way I have to build the speaker junction and switching relay circuit.  For the organ hookup itself, the D is 2 channel and the 204 cabinet is 4-channel, so first I was looking at using an active crossover to split the signal at the line level.  But, then I came across a 9-pin Leslie hookup on ebay - it was originally in a Gubransen Premiere (also a 2-channel organ) and was designed for a 102 cabinet (also a 4-channel cabinet) to plug into it.  It crosses over the main channel at the speaker level to split the lows/pedals off.  Of course it knocks all signals down to line level before sending out to the cabinet.  So, the crossover/audio output part will be relatively effortless now.  Unlike with the 102 cabinet, the switching voltage will be negative for the 204 cabinet (at least if I follow the "stock" specifications when building the relay/junction box) so I will just use the -13v magnet supply and hook switches up to that to switch the main and tibia from stationary to rotor.

It will take a while but at least I have some idea how to get it done now.

-jimmy

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Jimmy Williams
Gulbransen Model D, Leslie 204, hobby organist/technician