I was repairing a Fluke 289 with a faulty LCD, and the problem was actually easy to locate, the +20V rail was only a little over 15V. I disconnected the 0 ohm resistor R157 and used an external power supply to provide +20V, and now everything works fine.
I measured pin 3 of the boost chip U21 (LT1615), and the voltage there was only about 0.85V instead of the reference voltage of 1.23V I expected. A new LT1615 would save this Fluke 289, but the prices from Digi-Key and Mouser are too expensive, so I might go to LCSC.
It's just a simple 30 minute repair and nothing worth to talk about, what really bothers me is the choice of package size of the two voltage divider resistors R145 and R146 by the Fluke designer, R145 is 121K in package 0805, and R146 is 2M in package 0603.
Why?
![Confused :-//](https://www.eevblog.com/forum/Smileys/default/confused0024.gif)