Fluke 123, low light on LCD - Page 1
Forum section: electronics / testgear

author: ErikTheNorwegian
author_rank: Frequent Contributor
timestamp: March 25, 2014, 04:54:46 pm
content: I did

author: N2IXK
author_rank: Frequent Contributor
timestamp: March 25, 2014, 05:44:00 pm
content: IIRC, the backlight on those is electroluminescent. The phosphor in the EL panel itself could be worn out, or the inverter may not be providing high enough voltage to drive it properly.LED conversion would be cool, but probably more of a mechanical problem, trying to replace a thin flat EL lamp with LEDs.

author: Bunk
author_rank: Contributor
timestamp: March 25, 2014, 06:33:28 pm
content: Quote from: ErikTheNorwegian on March 25, 2014, 04:54:46 pmHey Erik. I too have a 123 scope meter. Sadly mine started to fail at around the same time as the internal battery died. Sometimes it will power on and work fine for 5 - 10mins, sometimes it just shuts down as soon as power is applied and sometimes when it does work only its only DC volts or resistance. All these scenario's are with the internal battery removed with the unit powered from its PSU.I'd be interested to see if you experience any of these issues? (Hope you don't obviously) I loved mine, while it worked!

author: SeanB
author_rank: Super Contributor
timestamp: March 26, 2014, 06:31:15 pm
content: Search eBay for CCFL lamp, and get one that fits, and install in the meter..

author: N2IXK
author_rank: Frequent Contributor
timestamp: March 26, 2014, 06:59:49 pm
content: The voltage to the lamp should be considerably more than 800 mV. Like several hundred volts. Perhaps a problem with the inverter circuit?Have purchased CCFL lamps from these guys in the past, with no issues:http://www.ccflwarehouse.com/ccfllamps.html

author: retiredcaps
author_rank: Super Contributor
timestamp: March 26, 2014, 09:31:44 pm
content: Quote from: N2IXK on March 26, 2014, 06:59:49 pmOver at badcaps.net, the feedback for ccflwarehouse.com services is excellent.

author: N2IXK
author_rank: Frequent Contributor
timestamp: March 27, 2014, 10:03:06 pm
content: Cool! Looks better than the display on those things ever did, IMO.Certainly the inverter transformer can go, along with the transistors driving it.You should be able to find the line that enables the inverter, and hack in a way to turn your new LEDs on and off using the existing backlight control circuitry.

author: tautech
author_rank: Super Contributor
timestamp: March 27, 2014, 10:58:37 pm
content: Great thread, thanks for sharing.

author: N2IXK
author_rank: Frequent Contributor
timestamp: March 29, 2014, 03:21:13 am
content: Guessing the "TLON" line into the IC enable pin is the on/off control line...

author: krivx
author_rank: Frequent Contributor
timestamp: April 29, 2014, 07:59:42 pm
content: Looks great. Any idea on how this will effect battery life?

author: kabul6969
author_rank: Newbie
timestamp: February 26, 2015, 04:08:57 pm
content: Hello Eric;I have the same problem with my fluke 123.with the original CCFL the light is poor.i open the fluke and if i disconect the cable the CCFL the fluke no lights. the CCFL is working but the light not shine well.what can i do?sorry for my English.