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Jenco Vibraphone (Posts / Post Isolators / General Maintenance)

harrysundown 17 June 2024

Hello!  First-time vibes & marimba owner here, both of the ~1960s Jenco 3-octave variety with the foldable legs.   I've done a bit of work on both to reduce buzz / rattle / ringing / squeaking with some success but have a few questions:

1) I'm finding both instruments have key buzz / muting that I've confirmed is due to keys rubbing against the post. On other forum posts, it's been suggested that old rubber insulators can be replaced to mitigate this.  Does anyone know where one might source insulators compatible with Jenco posts (see photos)?  Or, if not, a suitable rubber tubing I might cut to length and stretch over the insulators? Heat shrink is the first thing that comes to mind.

2) I found (especially on the vibes) that some keys were muted due to having essentially no room between the posts and so I bent the posts where I could to give a little space for the keys.  It did seem to produce an improvement, but it strikes me as the kind of thing that might be discouraged.  To be clear all the posts were more or less vertical to begin with, just too crowded.

3) Could anyone point me to educational material on lubrication of motor and shafts on an instrument of this age? The shafts themselves seem to have designated spots at the ends and halfway along the length.  (See photos). Am I correct in assuming these are meant for oil?  I would also expect the motor itself to need some ooil every now and again but I don't see any clear place to drop some in...

I have a few more questions but should probably save those for other threads.  Thank you very much -- any knowledge is helpful!

Brendan

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Comments

IndianaGlen Tue, 06/18/2024 - 16:44

Wow those look to be in amazing shape, what a couple of gems.

I may be over-explaining as it sounds like you’ve done some of this already; however, I’m hoping this will help others as well.

Others, feel free to comment, here are my opinions:

Your post insulators look like they have hardened with age. The best post insulators for Mussers, Deagans, and Yamahas are made out of silcone tubing. I can only assume it’s true for the Jenco as well. I buy the tubing on Amazon and cut my own (and for my customers) If you pay for postage, I’ll be happy to send you a few hunks to see what fits. Feel free to follow up on my Email (bluesnowandthen1122 at g-Maile dot com) My suggestion is to cut your own so you can tweak the length for your vibe. Usually you can pull off the old insulators with pliers, the really old ones may take some careful X-acto knife cutting. The silicone tubing is that works best on most vibes is white/translucent, some don’t like the color, you may be lucky since the Jenco looks like the posts are a little smaller and closer together. I wouldn’t use heatshrink, I think it’s too thin and may make noise. It wouldn’t hurt to try I guess, but you will have to heat it somehow near the rail. I only like to burn when I play :)

During moves posts get bent from time to time. I tap them back in place with a small hammer (GENTLY). I’ve never had an issue bending left to right but I guess there’s a possibility of breaking the post. I shake the bar back and forth and if a post is bent into the bar it’s pretty easy to feel. It looks like you have to remove the string to get the bars off (I have a Deagan that is like that). I use a sharpie to mark the posts I need to bend. Bending posts perpendicular to the rail can be dangerous. If you’re not careful you can split rail.

Lube:
Yes those holes in the resonator supports are for lube. After trying a lot of things over the years, my preferred lube is a SMALL amount of plain old SAE 30 weight conventional motor oil (E.g. Pennzoil etc.) --2-3 drops from an eye dropper. I re-lube every 6-12 months or longer. I just spin the fans to see if they move easy . I don’t know for sure about the motor. If the motor is quiet and doesn’t get too hot to touch after being on for a while, I’d leave it alone. If you need to grease something (like gears/shafts). A mix of lithium grease and gun oil works good. It’s thin enough to move into nooks and crannies, but still is a grease.

Motor:
Make sure you inspect the insulation of the wires! It can crack over the years, I’ve seem some very scary motors. I won’t give specific advice, but that may be a good place for the heat shrink :). If you know a motor ‘expert’ be careful. In most motor applications noise isn’t as critical as it is in a vibe. Changing the bearings, bushings etc. should only be done as a last resort.

Feel free to add questions to this thread, I’ll keep an eye on it for a while.

IndianaGlen

harrysundown Fri, 06/21/2024 - 21:45

Thanks IndianaGlen, very helpful. And that's very generous regarding the tubing. I ended up ordering some insulators from Century Mallet because I needed to order some other things anyway and I do think I'd probably prefer the black just to match the original style.

Regarding post position, I don't think any of my posts were noticeably bent and yet in a couple of places the keys had almost 0 wiggle room, which seemed to be to be muting the keys when hit. So I felt I needed to bend some of them out (where I could) to give them space. I can't seem to find any information about how much wiggle room is ideal between a key and its neighboring posts. I suppose this could also differ between vibraphones, but is there some rough rule of thumb?

Regarding the motor, it's not terribly loud and all the wiring/insulation looks like it's held up well. I am interested in trying to add a regulator to the motor (specifically to be able to slow it down) but I may start a separate thread about that, as it's less specific to the Jenco and more of an electrical engineering challenge. But if you have any experience there I'd love to hear it.

Thanks again,
Brendan

wyndorps Sat, 06/22/2024 - 06:02

Measure the thickness of your insulators. They look quite thick on the photo. They may have been replaced earlier and were thicker than in their original state. If you save just 1 mm of wall thickness, you gain 2 mm of clearance on each bar.

IndianaGlen Sat, 06/22/2024 - 11:26

IMHO just as long as there’s a slight wiggle/space between the bars you’ll be fine i.e. wiggle greater than zero. It’s on the node so as long as the bar isn’t pinched, you’ll be good to go. —good idea about getting the insulators from Century. I wipe each post with a damp rag (water) right before I slide the dampers down if they don’t go on easy dry.

It looks like you can move belt(s) on the pulleys to mechanically change the speed of the tremolo. You have to be very careful with trying to electrically/electronically change the speed of that motor. If it isn’t designed to be variable speed you’ll literally burn it up by trying to vary the RPM to slow it down. It would be MUCH safer to use a modern motor/controller set up and retrofit it to your vibe and save the original setup if you want to keep the vintage parts. I err on the side of caution; my rule of thumb is that if the motor is not connected to some kind of factory speed control already, then it’s not intended to be slowed down or sped up. There may be an electrical engineer that can add some insight; however, there’s some serious risk involved especially given the age of the motor.

For what it’s worth. A lot of players, like Gary Burton, don’t use the motor/tremolo. One can do a lot of learning, practicing, and playing without it.

-IG

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