FLUKE 123 - does not power up sometimes...

[Analogdevice]

Hello everybody.

Can you help me with this machine? Problem is, that the machine does not power up. If I push the on button, buzzer reproduces very weak beeps. These beeps are as weak, that you can´t hear it, if you have a closed case. It looks like the machine wants to power up, but something say "NO", so this is repeating again and again. If I pressed the up and right arrows and ON button, I hear a weak beep (once), so it means, that MASK software is running.
There are some detections:
1. I think that the machine does not power up in cold or hot temperature. Yesterday there were 21°C in my room and the scopemeter ran without any problems. Today I gave the scopemeter outside for some time (outside were 9°C) and then the machine doesn´t ran for some time. I found "LCDTEMP" in schematic of fluke and what so you think? May be the problem there?

2. If I push the ON button, D471 must recieve log1 to N501 - pin 62. This signal called POWONOFF and it can be measured on test point TP528. This signal is there, when the machine is opperationally, but when doesn´t power up, there is log0 and some pulses (see picture in the add.).

What do you think about it? Is there anybody, who knows to tell me, where I must find the problem?

Thank you very much.

[Analogdevice]

I almost forgot... When the machine are functionally, all circuits works correct, all functions performs. I measured slow ADC, charger circuit, flyback converter and it runs perfect. When the machine are not operational (I think when the buzzer beeps), the MASK software runs, because the charger circuit works and charged the batterry.

Second thing... When the machine was some time power ON, then I can power up it without any problems, so I think, that there is some problem with temperature.
Battery pack is OK, I have a new Ni-Cd cells on it.