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On Sun, 10/8/17, Reginald Beardsley pulaskite@... [hp_agilent_equipment] <hp_agilent_equipment@...> wrote:

Subject: RE: [hp_agilent_equipment] HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
To: hp_agilent_equipment@...
Date: Sunday, October 8, 2017, 9:19 AM


?











"The horizontal board is next to the tube and has Very
High voltage, The lack of horizontal deflection is normally
due to component frailer the 2 drive transistors that
provide the deflection to the tube and there drivers are the
usual ones that fail."



I bought a mil surplus Dumont 1060 (dual trace 60 MHz) scope
around 1990. A few weeks after the 30 day warranty expired,
the horizontal sweep died. After tracing my way through the
sweep circuit, the problem turned out to be fractured solder
joints. The Dumont was a 60's design with socketed
transistors as was the Tek 465 I used to repair the Dumont.
Both had problems with bad solder joints and corroded
transistor leads. I had an experienced Tek repairman take a
look at the 465. He whacked the frame of the scope with a
stick. I was a little shocked when he did that, but
immediately realized it's the best way to check for
intermittent connections. He started out by banging his
hands on opposite sides of the instrument before taking the
covers off. Just be careful that you don't damage
anything when you hit it. I learned enough from the Tek guy
to do the repairs on the 465 myself once I'd fixed the
Dumont.



If the sweep appears for even a instant when you whack the
scope frame you're hunting an intermittent. It's
tedious, but it means you don't need to replace
parts.



Whatever you do, do NOT spray tuner cleaner on the vertical
input switches. That's very bad for the capacitors. I
learned this AFTER I had done it and spent a lot of effort
cleaning things with 99% isopropyl alcohol.



Good luck and have fun!

Reg











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