Fluke 123, low light on LCD

[ErikTheNorwegian]

I did

[N2IXK]

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.

[Bunk]

I did get a Fluke 123 very cheap on the bay, just 200$, dead, but with power and one probe. The problem was a dead battery, removed the battery and the unit starts up ilike normal. new battery is on the way, but the LCD is very dark.
The LCD is very dim, so the backlight is low. Any body have som experience with this problem?
Is it common on 123?
I may put in some SMD LED`s.

Hey 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!

[SeanB]

Search eBay for CCFL lamp, and get one that fits, and install in the meter..

[N2IXK]

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

[retiredcaps]

Have purchased CCFL lamps from these guys in the past, with no issues:

http://www.ccflwarehouse.com/ccfllamps.html

Over at badcaps.net, the feedback for ccflwarehouse.com services is excellent.

[N2IXK]

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.

[tautech]

Great thread, thanks for sharing.

[N2IXK]

Guessing the "TLON" line into the IC enable pin is the on/off control line...

[krivx]

Looks great. Any idea on how this will effect battery life?

[kabul6969]

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.