Tag: 751

Premier 751 Vibraphone refurbish (part 2) (Job No: 1205)

The first part of this blog is 1205: Premier 751 (part 1)

Looking at the pedal bar, shows one reason for the wobbly frame:
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This bar joins the bottom of the vibe together, and is the fulcrum around which the damper pedal rotates.  The two plastic ends have a locating peg inside a profiled end to suit the leg frames, the hole (pictured) at either end accepts a “J” bolt which is tightened to secure the whole frame.  As can be seen, the holes in the very thin walled tube get badly worn (on the left it is broken out, relying on only the plastic insert).  If the legs aren’t held in place securely at the bottom, there is obviously no chance that vibraphone will be stable.

The good news is this has inspired me to write a blog about my top ten bad designs. In which the Premier 751 vibraphone appear twice, because the second bad design concept is using the resonator tubes as a structural element.
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The front row of tubes form a diagonal line from the low notes to the upper notes, this diagonal can be utilised to make a triangle which are very strong.  Triangles are very strong, which is why they are seen on all of my frames, and why I give a lifetime guarantee (my lifetime).  The problem with the Premier 751 vibraphone is that the resonators are fixed at the high end (if you disregard the rubber band!), in other words the peak of the triangle is open, so its not really a triangle at all, and therefore not strong at all.

So, the non triangle combined with a badly attached bottom bar results in a frame that wants to wobble, and succeeds really well.  It’s a good job they came to me with it then, isn’t it?  What I have done is make a bar to fix the legs, thus creating a parallelogram – the notes rails, and the pedal bar being the two parallel sides.  A second bar hinged at the top of the leg frame, and fixed on the first bar creates my (integral) triangle for strength, and prevents the legs from going rhomboid.  Simple (but its how you apply it that makes the difference!)
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What I find annoying, is having to re-do other peoples repairs. This vibe had loads of issues, lots of little things that someone had made a dogs dinner of. For instance:
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Welding and soldering the butterflies on. Between the butterflies is where the fan shaft runs through the central bearing. Now it has welding marks, and filing marks, and guess what, now it has an annoying “tick, tick, tick, tick” sound as it rotates. I have spent the time to clean it all up, and it is nearly gone, but essentially the fan shaft is ruined.

Anyway, rant over. After repositioning the damper springs, that were put in wrong (in fairness, these were not of consistent quality as a spare part when they were available), and re felting the bar, and the notes cleaned, the vibes are done.

For the remaining time the vibes are sitting in my workshop, I bed the notes into the new felt. I leave the connecting rods off the pedal, set the damper bar high, and pull the notes down with a clamped beam.
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Premier 751 Vibraphone refurbish (part 1) (Job No: 1205)

This set of vibes needed a bit of tlc, or in other words a complete overhaul.

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There are a couple of issues that the customer specified that need to be looked into:  it’s really rickety and unstable, and the motor keeps snapping belts.

Whilst I was stripping the instrument down to service the parts, I drew up a long list of other problems.  Some faults I repair immediately, whilst other issues I put to one side to be looked at in isolation.

For instance:
The speed controller has been taken apart by someone and re-assembled incorrectly, so there was a bolt floating loosely around the main terminal block  which should be securing it.  Idiots!
The mains power lead going into the transformer housing has a slice through the insulation (on both the live and neutral (brown and blue) wires).

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Along with a couple of other issues on the motor wiring, means that the whole lot was removed to be looked at later, because whoever did it was trying to kill someone!

What I tend to do is overhaul the frame first.  This is both because it is big and takes up most of the bench, but also so that everything else gradually gets put onto it until I have a complete instrument ready to be checked.

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The photo above is looking down the length of the instrument at the low end.  You will have to zoom in.  I put a straight edge on top of it to show that it is bent all over the place.  This not only looks bad, but the deformation is primarily where the legs attach (probably one reason why the instrument wobbles badly).  Straightening this is a good job to do on a cold morning – I have a forming bar, a hammer, an anvil and a pair of strong arms…

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This never comes out perfectly, but it certainly gets close to straight, and once it is put back on the instrument, it will no longer be that noticeable.

The story continues in: 1205: Premier 751 (part 2)

Premier Vibe Motor Conversion (Job No: 1101)

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This is a replacement motor unit made for a Premier 751 vibraphone.  The on/off switch, and potentiometer are on fly leads so that they can be fit either side of the leg hinge, on the underside of the high end transom.  The grey box contains the speed control PCB, capacitor, and various connectors, with an IEC socket fitted so that the power cable can be removed.

The motor carriage is made to fit 750 & 751 vibes, but will probably fit older models.  Like everything I make, it has been designed to overcome problems that I have had to repair many times.  This carriage is not only strong enough to actually hold the motor, but will actually stiffen the note rails and their joining piece.

Locating the pot and on/off switch to the end frame avoids the normal difficulties experienced when bowing the notes, and the leg hinge will offer protection to the components during transportation.

The grey box is the brains.  The IEC socket was a moment of realisation during conversation with the customer.  By using a standardised socket as opposed to permanently wired, prevents straining or damaging the cable which occurs when winding it around the instrument, and makes replacement simple.  In fact finding a replacement cable on a gig is now simplicity; just borrow the cable one powering the kettle, or pc, or guitar amp, etc, etc.  Additionally, there is now no need for anyone other than myself to open that grey box!  Finally, there are two small holes on the side, the small one is the power led on the PCB, the larger one is access for the trimming pot which can be used to increase the maximum speed, so can be ignored.

To fit it, six holes need to be drilled, four for the motor carriage and one each for the pot and power switch. Then its just a matter of routing the cable.