HP 8013A

[Jackson]

Hello,

I came across an old 8013A at school that was on its way to the dumpster and decided to grab it and see if it still worked. Everything seems to be fine with the exception of the Rate (Hz) slider switch. All the other switches slide and then click into place whereas the frequency switch takes some jostling to get moving and then doesn't "click" into any positions - it just stays on one range setting even though the contacts and switch are sliding. I've opened it up and it seems that there is a little metal pin/tab that looks different from the other switches below it. I'm guessing that this might have something to do with the switch clicking into spots but I am not sure. The metal pin on the broken switch looks like it is hanging down more (see the attached picture). Does anyone here have experience with these switches that could offer up some knowledge on their inner workings?

Thanks,
Jackson

[wn1fju]

I hate these HP slide switches!  What you have to do is remove the front panel from the unit and then separate the board from the metal
front panel.  You will then see all the switches and the mechanisms.  Now you have to slide each switch all the way out one end.  Be VERY
careful when you do this, because if I recall, they tend to hang up on solder bumps if you slide them out the wrong direction.  Carefully note
the position and orientation of each switch before you slide them out so you can reverse the process upon reassembly. 

With luck, all that you will find is the switch covered in dirt and grease - a simple alcohol wash of the switch fingers and the underlying gold
trace that the fingers slide on will cure your problems.

Worst case is that one (or more) of the switch fingers is broken or gone.  The only way I've been able to fix that is by scavenging from another
switch.  You can heat stake a tiny piece of metal to simulate the finger if you can find a suitable piece of metal.  Of course, if the underlying
gold trace is severely scored, then you are completely out of luck as no contact will ever be made.

There's nothing really complicated to the mechanism and it will all be clear upon disassembly. 

[The Doktor]

Here's a picture of the switches in my 8013b, hope it helps.

Ed

[Jackson]

Thanks to both of you for the information. I finally got around to looking at this again today. I de-soldered enough wires to slide the switch in question out (as you recommended) and found that the metal pin was hanging loose by one end (like the second switch down on the right side in Ed's picture). I popped it back into place, slid the switch in, and it seems to be working great! It still doesn't "click" into a setting (I'm guessing because the pin is old and deformed), but it slides smoothly and switches between ranges now (the TDS340 was on AC coupling when I took the picture, which is why it doesn't have nice square waves). Now I just have to remember where all the screws go back in and I can move onto repairing/calibrating the pile of equipment I recently acquired off of craigslist...