Fluke 87 Backlight issue...

[Pete66]

Hello,

I've been lurking around this awesome place and finally decided to register. 

I have a small annoying issue maybe you guys can help me with.  I recently purchased a broken Fluke 87 on ebay.  I fixed it and calibrated it and it works great but there is still one annoying issue I cannot figure out.  When I press the yellow button to turn on the LCD backlight it turns on no problem.  However, when I press it again to turn it off it doesn't turn off.  I have to turn off the meter to get the backlight to turn off.  Pressing the yellow button again does not toggle the backlight off.

According to the schematics Q5 and Q7 control the backlight.  I tested them and they are both good.  I'm not sure what the deal is.  I'm beginning to think it is a firmware issue.

Any ideas?

Thanks,
Pete

[coromonadalix]

may help  ??

http://mebert.org/entry/3

[odessa]

The older Fluke 87's work like that ( yellow button for backlight ) and it just stays on .

The newer ones ( black button with illumination logo ) you can set to two brightness's then off again pressing the button.

[mzacharias]

Normal operation for a series I. The backlight times out after about 52 seconds, if I recall.

Or just turn the meter OFF and back ON again.

[Pete66]

I guess that's how it is supposed to work.

Thanks
Pete