Mitutoyo 293-768-30 0-1" digital micrometer screen replacement

[mjk]

Just picked up a Mitutoyo 293-768-30 0-1" digital micrometer at the local farmers market.
Tan with foam case vintage, last calibration sticker 2005
Mechanically and cosmetically it is pristine lines up with 0" and 1.000" using a standard
When I bought it(as is) there wasn't a battery
Loaded a fresh battery and the lcd has a 90% of the character "pixels" missing, but they do show movement

Are the screens worth replacing?

 

[neanderthal mach]

No idea of cost for a new screen, but if it's as pristine as you think, there's probably little else that could be wrong with it other than the electronic board and that screen. After a bit of thought, your issue sounds like some I've read details of where the LCD has been exposed to cold enough temperatures to bugger up the display.

Where you are a Mit. repair center wouldn't be that far away. I'd get a parts cost for a new screen. If that's within reason then I think I'd take a chance and get at least that. Given the full replacement cost for a brand new mike, it might not be cost effective if you've got to do even more such as replace the internal board. Unless I'm missing them, that model doesn't seem to be in production anymore. So parts may or may not be even interchangeable with the newer models. Wish I could be of more help, but answers from a proper repair tech would be much better than anything I might think of.

 

[Bakafish]

Very unlikely there are parts still available for something that old. Any repair facility is going to charge more than it's worth, even assuming they could fix it, so there is little to be lost from attempting your own fix.

I've never had one of that series opened, but what you are describing is often caused by a thin elastomeric bridge between the circuit board and the conductive elements on the glass of the display itself. These are known as Zebra Strips because they often have visible alternating stripes of black conductive carbon and white rubber. Being rubber, age can cause them to harden and shrink causing loss of connectivity between the two surfaces. There are various ways to resolve this, replacing it with a new strip (if the dimensions are correct they are relatively interchangeable by design), shimming the screen to restore contact, or 'conditioning' the rubber to restore its elasticity. But start with a gentle cleaning with pure alcohol on the circuit board side of the contacts of the strip and the board (the strip will usually be stuck to the glass side due to age and should only be removed once this cleaning and shimming fixes have been tried first.)

 

[mjk]

Wasn't to hard to take apart(over a white towel to catch the tiny screws)
Screen and board are "sandwiched" together, back of lcd not accessible
New parts not available(Mit offered a 25% off list of its current model)
This will now be used as a mechanical micrometer as it still is accurate thru the 0-1 range

 

[TGTool]

Put an eye patch over it then and call it a pirate mic. "Aaargh" when you take a measurement should work.

 

[Bakafish]

Wasn't to hard to take apart(over a white towel to catch the tiny screws)
Screen and board are "sandwiched" together, back of lcd not accessible

Would have loved to see a picture of that board to give further input, the LCD to board interface is the likely suspect and is rarely assembled in a non-reversable way.

New parts not available(Mit offered a 25% off list of its current model)

I expected as much. Mitutoyo seems to aggressively deprecate and erase the existence of older products. Even manuals, something that could be archived at little cost and great benefit are often impossible to find. This is a very Japanese way of doing things, I wish it were not the case.

 

[mjk]

Ok Last Sunday while drinking my first cup of coffee I checked E..bay to see if it was worth selling the mic as is .
so happened someone had a NOS display for sale.
Slightly different model, but same series, with a couple more buttons.
For $29.99 delivered I took the chance. I had $15 in the mic, what can I loose
15 minutes after opening the box, I have a working display
Pics show the old display and the new after installed at 0 and at a 1" std
The side view of the "board" is what I thought was sandwiched together. The blue buttons are actually a molded sheet to waterproof the mic and also "stick" the board together after several screws are installed.
Pic of the LCD by itself, no numbers
I think I did good for $44.99 (ok calibration nasayers....let it rip)

 

[Bakafish]

It used a zebra strip as expected. Glad you brought it back from the dead.