Home Up AMPEG SVP-Pro AudioTronics Carvin DMX MX3282A eDrum kit




This is my first Mixing board that I owned.  I am restoring it to functional shape. I can not find some of the slider pots in lots less than 230 units.  So I must substitute an illuminated slider to maintain the travel and resistance.  

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This board has multiple bad pots, intermittent connections and dead channels and outputs. 

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Restored with the new pots. All channels and outputs fully functional!

IMG_4130.JPG (344326 bytes)   Old School dual spring reverb.

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Do not forget to shut off the reverb return before sliding the mixer across the table during the gig. 

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I replaced two OP amps to restore channel and the Left main output function. 

scan0007.jpg (2963644 bytes) scan0008.jpg (3429470 bytes) scan0005.jpg (3260279 bytes) scan0006.jpg (3289538 bytes) scan0009.jpg (2363529 bytes)
scan0010.jpg (2841064 bytes) scan0011.jpg (2691472 bytes) scan0012.jpg (2593039 bytes) RC4558 Op Amp

Slide pot w/LED for tone controls.

Slide Pots for audio sends.

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Restuffing of the slide pots.  

There are no inexpensive direct replacements for the 50K ohm tone controls.  They can be ordered at a minimum of something like 230 pcs.  But I need only a small fraction of that amount.  so I located a 50k ohm slide pot with the same taper and slide length.

While thinking about how to mount and run extension wires from the circuit board to the new smaller slide pot genius struck me.  Why not put the new pot inside the gutted old pot?  The old shell will keep the new pot physically aligned and provide a clean connection to the circuit board.  See below:

IMG_4164.JPG (315622 bytes)The new pot is considerabley smaller than the origonal 50k tone pot.
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Much different wiring too. 
IMG_4170.JPG (255733 bytes)While looking at this comparison an idea hit me!
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Is it possible to put the new pot inside the old?  Then run lead wires to the original PC solder tabs??!!
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YES, it is!
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Lots of room to spare.
IMG_4163.JPG (356538 bytes) Clean the decades of dirt off of the circuit board.  Non residue contact cleaner.
Not seen is Caig DeoxIT.  Each pot is treated with this product.  I need to pick up some fader lube.  The slides are sticking.  
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I tried different stuffing methods. 
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Looks nice. 
IMG_4177.JPG (328333 bytes)Rough up the metal with a Dremel tool and a tapered stone. 
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This did not work well and takes a long time 30 mins to set up. 
IMG_4186.JPG (188293 bytes)Hot melt glue works great.  Tapered tooth picks help center and hold the new pot in the old shell.
IMG_4180.JPG (288597 bytes) This looks great.   I did not include the brown plastic dust mask?  I fear it will jam up the works later.  
IMG_4187.JPG (269825 bytes)Solder lead wires.  Insulate with heat shrink.
IMG_4191.JPG (290059 bytes)I used thin, solid telephone wire.   I figure the gauge is about 22 or 24.  I have to measure and verify this. Work fast with the soldering iron. The insulation is not made to withstand the solder heat. Position the wires so mounting screws do not pinch them.  
IMG_4193.JPG (261577 bytes)Extend the wires through existing holes. I kept a loose color code.  Green for the negative LED lead and Red for the positive LED lead.  A single color for the resistive element and a fourth color for the wiper.  It helps keep things straight. 
IMG_4194.JPG (258307 bytes)I first wrapped and soldered the wires to the old tabs. I later just fed the length of bare wire though the PC hole and soldered it down along side the solder tab.  
IMG_4195.JPG (357451 bytes)The PC holes accommodate the added wire thickness. The LED leads are dressed for possible future use.
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IMG_4200.JPG (375223 bytes)One down.  Ninety Five to go!  The re-stuffing should go much faster.  I took my time experimenting to find a good solution. 


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