This is not technically a repair thread. I am in the process of repairing and old Keithley 2002. The repair pushed me to make a DIY tool that might be useful for others. So here I am sharing the experience and construction.
The repair required me to pay close attention to some minute details on the board. I do have a 7x-40x inspection stereo microscope that is excellent in itself. It has drawbacks of only having a limited space available under it, limited reach and limited viewing angles. Fully articulated mounting arm for the microscope would help, but they are hard to find and cost more than my microscope.
I also have a 10x triplet loupe (Belomo x10 from Amazon). It is also very good, but has a very short working distance. On a fairly three-dimensional circuit, like Keithley 2002, I could not physically get close enough to what I needed to see.
Therefore I decided to make a small handheld microscope that would combine maneuverability of a loupe and working distance and stereo view of a microscope.
I started by buying a little toy-like microscope on eBay.
http://www.ebay.com/itm/20X-Binocular-Stereo-Microscope-LED-Light-For-Circuit-Board-Lab-Phone-Repairing/122434659671 They usually sell for about $50, but it was on sale and I paid $35 delivered.
This microscope has few clear advantages for the job:
1) While toy looking, it has real glass optics and it is fairly good.
2) It is very light and this is important for a handheld operation.
3) Because objective lenses are small, it transfers less light and more importantly allows more of depth of field for viewing three-dimensional structures, like PCBs.
Undoing four tiny screws allowed me to quickly separate the stand and the light from microscope. The focusing knob was removed by unscrewing left side against right side of it.
Light that came with microscope was not very good and also required 3 batteries to run it and that is weight and bulk. I decided to substitute it for a cheap focusable flashlight I got from Amazon. The plastic stem of the microscope was cut with Dremel by hand to make space to mount flashlight at 45 degree angle (horizontal cut and then half rounded opening from the front). Now a simple tie wrap can be used to hold flashlight in place. This mounting still allows focusing the light, turning it on and off and also changing the battery without a need to detach it.
Being handheld, this does not require a focusing knob, as focusing is done with your hands. This is all.
This worked very well for me. At 20x magnification I can still handhold it and able to inspect boards from strange and unusual angles. 3" working distance is very comfortable. The microscope can be used with flashlight on top, or turned 180 degrees with flashlight on the bottom depending on the best angle for your piece. If your hand a little less stable, you might consider 10x magnification instead of 20x.
Later when inspecting new and very shiny PCB boards, I discovered that light from flashlight could be at times too harsh. The easiest solution was to use a Ping-Pong ball and make a hole in it that is roughly a diameter of the flashlight. Now we have a removable soft box in front of your light source.
For a grand total of about $40 and 15 minutes of work here is a tool that I keep using over and over again. Pictures are below. If you have questions or comments, please let me know.
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