HP 5335A frequency counter repair

[rob2630]

I have just got an old HP533A counter and it works fine, or at least the bits I want work fine. However, the noise from the fan puts my vacuum cleaner to shame. I have plenty of fans that will do the job but there is another problem, I can't get the lid off the counter. I managed to remove one side, the air intake side and that required a lot of persuasion presumably because it is old. Can someone tell what screws I need to remove and how it comes apart before I take a can opener to it?

[Dr. Frank]

Should be described in the manual.
It's one screw on the back side, centered on the edge (bent around) of the top plate.
Undo the screw (won't come out completeley), and pull (shift) the top plate backwards.
Easy.

Fan always has to be replaced. Check your 5335A vintage / version, either 110V or 24V type, again see also manual.

Either buy original Papst one, or replacement. See foregoing threads about the 5335A, with photos.

Frank

[rob2630]

Thanks Frank, now you have said that I know where that screw is, under the "Do not remove" sticker! I should have known to look there first. I have seen the other posts on this subject which is why I joined this site. As far as I can make out the counter is 1984 but in clean condition. As I say, thanks for your help.

By the way, the manuals I have been able to find so far do not mention taking the thing apart they just say remove the top cover. The fan as far as I can see through the back is marked 30v. I will measure tonight and dream up a suitable replacement.