Some time ago I bid and won a large lot of Tektronix and HP plug-ins at eBay. One of them was a Tektronix DC-510. But it had some problems, as very low sensitivity (you needed roughtly a volt to get a measure!) and a semi-functional keypad.
First problem (sensitivity) was tracked down to a faulty BNC connector soldering. In the picture you can see the cracked connection:
Once resoldered, sensitivity was OK!
Other problem, which seemed as a minor one, was an small nightmare!. When I got the front panel out, a myriad of parts got loose!. Some of them were evidently broken... how could I fix them???. Solution was in the stapler. What???. Yes, the stapler!. Here you can see some parts and a couple staples, one of them bent... do you start to see the solution ;-)?
What I did was a belt for each broken key. In order to fix the staples, I used some epoxy. Here you have a detailed view:
And some other views of the keypad:
*** WARNING *** as staples are conductive, you should be careful about shortcircuits with circuit traces.
Here you have the keypad attached to the front panel:
And, if you are like me and enjoy looking at the innards of finely made test gear, here you have some pictures:
And then, the final result in a TM-5006 :-)
Success!!!