most broken equipment you run into?

[coppercone2]

qualified to work in a body shop after only 15 deliveries

[lugaw]

It looks really really bad on the outside but miraculously the inside survived without damage and it is very accurate because of the year 2020 calibration.


I also had a Tektronix AWG615 that looks pristine on the outside but has a shorted 3.3v rail I can't fix. :/

[RaymondMack]

In my experience, anything mechanical will become faulty at some point. Particularly silver coated switch contacts. I have probably spent more time replacing and/or cleaning damaged/oxidized switches and bad capacitors than bad ICs. I recently repaired 4 different Agilent E36xx series PSUs (approx. 2008-2011 MFD) that had faulty "gold plated" switches made by C&K (on the back side for slave/master operation and remote voltage/current programming). Ended up just putting wire jumpers in place of the switches since they were so damn expensive to replace (replacement switches would have costed more than I paid for the PSUs).

Slide switches are pretty easy to mangle from excessive force and most are not sealed well (if at all), allowing atmospheric gases to easily reach the contacts and induce oxidation. Many, HP/Agilent PSUs use these.
Rocker switches can seize (contacts weld together) in AC mains switching (the contacts generally fail before the rocker action does).
Toggle switches are fairly robust, but are easy to hit and damage accidentally.
Rotary switches are robust mechanically, but oxidize the easiest and are a pain to clean.
Large push button switches are quite fragile (especially locking types). I mostly see the plastic stems break off or the push mechanism seizing from either dust/contaminates or mechanical wear of the track.

Since most analog PSUs (especially from HP/Agilent) have at least one or more of the above switches... I'd vote analog adj. DC PSUs as the most likely to fail TE.

[coppercone2]

and sealed relays don't do too well either.. they often have vent holes. its not a good feature

basically its a vent for whatever the switch makes switching

if you seal it up things get trashed

[KrudyZ]

I also had a Tektronix AWG615 that looks pristine on the outside but has a shorted 3.3v rail I can't fix. :/

Because you can't find the location of the short or why?

[ifonlyeverything]

Lately, it's been much of the stuff that I purchase on ebay. Badly packaged by careless sellers

Went through this with SMPS transformer ferrites and AliExpress sellers. Three different sellers, in fact. Careless idiots.