Fluke 867B - doesn't enter set-up mode

[asava]

Hello,

I picked up a Fluke 867B, and it fails to enter set-up mode. In rest, it seems functional.
Does anyone have an idea what it could be?
I tried cleaning the contacts on both sides of the rotary switch, but the problem persists.
I attach a photo with how it looks in set-up mode.

Any ideas are welcome!

Thanks!

[Wytnucls]

Mine has developed the same fault now. I haven't had time to troubleshoot the problem yet.
The maintenance manual is available online, if that's any help.

[mzacharias]

Mine did that and I wasn't able to fix. I replaced a cap or two inside - no go. Sold "as-is" on eBay. Other than not entering setup, it worked fine; just could not change any default settings.

[mahi]

Exactly the same screen is shown if you hold the dial between any two positions. So at first glance it looks like the multimeter does not detect the rotary switch is in SETUP position.

The circuit to read the dial position is quite simple so it should be easy to confirm whether the switch works okay.

[Wytnucls]

Yes. The switch is a voltage divider, presenting a varying voltage on pin 83 of U25.
Hope U25 is not the culprit.

[Wytnucls]

Fixed!   

Tested all the values of the resistors around the selector switch.
Found R166 (component test) reading a bit low, at 4.5K ohm, instead of 4.99K ohm.
Cleaned the resistor with electronic cleaner. The resistance only went up a little bit (4.6K ohm), but that was enough to activate the right sequence in U25.

[Wytnucls]

Vdd is 5.2V
R170 (Logic) 49K9 reads 12K0 on mine.
R168 (Setup) 6K0 reads 5K2.
All the other resistors have the correct values.

Smoothing cap C64 (Ceramic 10% 25V X7R 0805) should measure 0.1 uF.
I couldn't find TP22 (40 MIL test pad) to check the voltage to pin 83 (U25).
 (Update:Test pad 22 is on the reverse side of the PCB close to the selector switch)

I would recommend cleaning all resistors and PCB around the selector switch before replacing anything.

[eduaqa]

I know is a old thread, but what I have seen is that sometimes the copper track between the resistor and the rotary "island" don't contact well,
too measure the real resistance of the rotary position, put the rotary on the position you want to measure and measure between the "ground" on the rotary connected point and on the point where the track goes to the u25. Measuring the resistor directly on their soldering point does not measure the real resistance of the voltage divider