Keithley 2110 back lit

[hitecelec]

Hi

I have a unit functioning perfectly except for the white back lit. suspect the rectangular back lit module beneath the display
. the number written on the back lit RFWO69322G2 V1. any clues?

thanks in advance

[rtekal]

I also have the same problem. Instrument is good, but no display on LCD as the backlight is not working. The back light is a separate module that is mounted behind the LCD.

Is anyone having schematics or solved this problem?

[tooki]

Not having any specific knowledge of that meter model, the first thing I'd check is the backlight LED itself:
1. is it getting power? That's easy enough to measure.
2. Remove the backlight and test it on its own. Does it light?

If the LED itself has gone bad, just dremel it out of the backlight panel and then epoxy in a new LED.
If the LED is fine, then start looking at whatever is driving it.

[voltsandjolts]

So, failing backlight LEDs seems to be common issue with these Keithley 2110. I've seen it on a couple of units, but they've been on permanently for >5 years, so it's wear-and-tear rather than a fault IMO.

The light comes from two small PCBs mounted at each end of the plastic block "backlight diffuser". See attached photo. One of these PCBs is 'surface mounted' on the display PCB. The other is through hole and is trickier to remove - I just snipped the legs going into the display PCB. There are some clear plastic tabs that need snipped out too.

Anyway, replace the three SM0603 LEDs on each backlight PCB, refit and its job done. Quite easy.

Make sure the PCBs go back on at their original location, i.e. putting them back on the wrong side of the LCD will reverse polarity, won't work.