Issue with my Fluke 79 III

[bat]

Hi guys,

I recently acquired a Fluke 79 III that was going to be discarded, and I've noticed a few issues. The range and yellow hold buttons don't work properly. Sometimes, the hold button works when I press hard enough. I took it apart to have a look, and the contacts seemed to be in good condition. I used a small metal rod to trigger the contacts, and indeed it worked, but it was also failing intermittently. My concern is that the issue might be deeper within the electronics.

I have attached a few pictures. I would greatly appreciate any tips from you guys.

[Greybeard]

I don't see your pictures.
Have you tried to clean the rubber contact and the contacts on the PCB?

[bat]

I attached a zip files with my pictures, but it seems that it did not work.
I have cleaned the rubber contacts but couldn't clean the contacts on the PCB. How did you manage to remove the grey plastic cover ?

[Greybeard]

How did you manage to remove the grey plastic cover ?

That is not my Fluke 79 III, that's what google search found:
https://minhcnguyen-blogspot-com.translate.goog/2021/02/ben-trong-dong-ho-do-dien-van-nang-fluke-79.html?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=wapp



How did you clean the contacts?

[bat]

Thank you very much mate, I didn't even think of trying to search on youtube for that lol 
It's now operational 

[Greybeard]

What caused the problem?

[bat]

Contacts (hold & range) were dirty, previous owner used it in a very dirty / dusty environment and never cleaned it.