One of my two 5LX's is of the older type (much older than I thought!)
What this is is an original Studio 5 that was later modified into a 5lx with a firmware upgrade. The later ones gained the separate PSU board when somebody finally went "D-oh" and realized it was much easier and cheaper to build different units for worldwide distribution that way than to have different assembly runs for different countries. They probably outsourced the new PSU's already assembled from a supplier for the same reasons.
The older units transformer is buzzing audibly (albeit when you're close to the device) and I'm concerned that this might indicate inevitable failure at some point.
These types of transformers buzz because the enamel lamination surrounding the winding has cracked here and there and become a tiny bit loose. You're hearing a 120Hz buzz - the 1st harmonic of the 60Hz line frequency. This buzzing, albeit annoying, does
not necessarily spell doom for the transformer. It can often work this way for the life of the unit without failure.
What I'd like to do is remove the existing components and replace the entire PSU with an off the shelf switched mode PSU that supplies the right voltages at the required current level.
The practical solution is to repair or replace the transformer
only. Possible repair methods include, in this order, depending on the severity of the buzz, simply inserting rubber standoffs/grommets under the transformer, since the sound is being amplified by the vibration being transferred to the chassis. This often cures the symptom in 5 minutes or less. Since you say you have to be "close" to hear it, this will very likely do the trick. If the transformer isn't sealed in a metal can, you can attempt to drip a sealer into the windings to stop the noise. (Because the buzz is actually the overlapped windings of thin metal plates buzzing against each other as the magnetic flux varies with the AC) This can be an epoxy mixture, a superglue or even a basic wood varnish. The main requirement is that it be very low viscosity (thin) in order to be able to seep into the layers as far as possible before drying and reasonably heat-resistant, which most glues and such are.
Failing those, you might consider
simply replacing the transformer with an equivalent. There's almost certainly a part # you can cross-reference. Plus, you know the primary is 240v and you can measure the secondary voltage with a multimeter. The current rating will be roughly 2/3-3/4 the internal fuse rating and you'll want something roughly the size of the one you're replacing. This is far, far simpler, safer and more practical than shotgunning the entire PSU.
I'm quite confident at hacking/modifying things so I'm not likely to be stressed by the tasked at hand. However, I'm not an electrical engineer and don't have the knowledge to work out the PSU requirements myself.
(assuming I don't fry myself and/or the LX5!).
I sure you wouldn't be so eager to hack on something you admit you're not qualified to if you only had
one 5lx. While the reliability of these old beasts is generally very good, it really doesn't pay to risk "frying" one unnecessarily. Do you have so much MIDI that you need two units running simultaneously or is it just a spare? Try curing the buzz with the above steps first. If it doesn't work you can then resort to "hacking" more of it.
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Topic: Studio 5LX PSU (Read 6955 times)