Lexicon MPX550 Encoders

[AcdNrg]

Although the corresponding Service Manual is pretty verbose, there is NO info on which type of encoder is being used. I found some info on how to repair jumping encoders, but in case this doesn´t work I´d like to have some spare parts available. Does anyone know, which encoders were used and where I could get them in 2024?

edit: Forgot the NO in my original post ^^

 

[Khron]

Some photos and measurements of the originals would help, as well as details regarding detents (if any).

 

[AcdNrg]

Some photos and measurements of the originals would help, as well as details regarding detents (if any).

Will add these asap, just unpacked the box this morning. Stay tuned

 

[AcdNrg]

Here you go, feels like 16 dents (12 o´clock to 12 o´clock so maybe 15)

 

[NoisyIndividual]

Hi, just wanted to say that I tried the Grayhill 25LB22-G and it works! They have em on mouser!

This from a thread asking about the encoders on an LXP 15, it is likely this is the same part.

I have an LXP15 where the encoder was bad, and the Grayhill part fixed it.
Although it wasn't quite a part for part replacement, the one I got from Mouser was a vertical type, not horizontal, but I modified it to fit and work well.

https://groupdiy.com/threads/lexicon-lxp15-repair-broken-page-selector-encoder.74088/

 

[Khron]

Is that an encoder though, or technically a hexadecimal switch, going by the wipers / etched pattern?

 

[NoisyIndividual]

Its a Gray Code output device.

 

[AcdNrg]

I will check that mouser part for spares and also get some education on encoders, gray code etc. The fun of self learning . Can someone point me in the right direction to understand what the difference between hex-switch and gray code output device is? Or is that an in-joke ^^

The good news (for now):

I was able to shoot all troubles and got the 4 encoders working again. Good as new, no jumping, no hanging, just working as you want them to.

After disassembling the MPX I carefully opened one of the encoders: guts and shaft were soaked in some sticky, brownish residue. Not sure if from nicotine or some contact spray, but isopropanol and distillied water removed all the gunk. Rinse and Repeat for the others, now the MPX is back to normal.

I´m saying "for now" because it has to stand the test of time. But things look good. I learned a few things in the process. Thanks for being a great community and supporting me in my first steps!

 

[NoisyIndividual]

I think the whole reason for Gray Code devices is that any errors due to a warn or dirty device can be detected in software and ignored/corrected to a certain degree.

Probably no longer relevant for todays audio gear, but this may have been an issue in a Polaris missile system or some such.