Bun's Lab – Telegram
Bun's Lab
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Electronics projects, vintæg computing, programming and repairs. A minimalist blog of sorts.
@BunsGarden @BunsNook
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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
Take off these nuts and desolder the input BNCs, then you are finally in.
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.
y offset pots also have issues
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Oh and the defect in the second channel was just a bad connection
Getting it back together is an even bigger pain in the butt, since you have to align all those buttons and knobs simultaneously.
One Hameg engineer to the other: "we need a variable capacitor here with x pF but the only ones I can source are a bit pricey".
"Oh just twist some wires together, it'll do the trick just fine."