The second channel of my workhorse analog scope went out. I figured it'd be a simple fault not worth talking about (it was). But opening this thing to get to the input stage is a pain and a half.
I keep it around as a burner, where I can blow up the input stage on accident and fix it with readily available parts. Unlike other vintage oscilloscopes that use unobtainable custom hybrid ICs or my modern DSO that would be a paperweight then.
I keep it around as a burner, where I can blow up the input stage on accident and fix it with readily available parts. Unlike other vintage oscilloscopes that use unobtainable custom hybrid ICs or my modern DSO that would be a paperweight then.
First you have to pull off all the knobs and also desolder a bunch of wires. Yes, desolder. There is no connector.
Then there are these hidden screws. After taking them and two obvious screws in the front out you can slowly wiggle the input stage unit out of the case
The input stage of this 20Mhz bandwidth scope consists of a simple TL051 JFET input OP amp and a UA733 differential video amplifier. Yes a video amplifier. Amazing.
These old Hamegs suffer from what are now very fragile plastic pieces. The sensitivity vernier potentiometers are connected to the shafts by plastic pieces which cracked on all scopes of this kind that I've seen.
Since I don't own a 3D printer yet, I fixed it with glue and multiple layers of heat shrink to hold it together. It holds, for now.
Since I don't own a 3D printer yet, I fixed it with glue and multiple layers of heat shrink to hold it together. It holds, for now.
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Oh and the defect in the second channel was just a bad connection