HP 7044A X-Y Recorder Restoration

It takes another long video full of analog goodness to repair this X-Y recorder beauty, because we end up fixing it twice! We also rejuvenate the pens while we are at it, also using two different methods.

HP 7044B and 7045B Service Manual: https://archive.org/details/hp-7044-b...

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"Elevator Music" Credit: Crinoline Dreams by Kevin MacLeod

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00:00 Intro, previous HP 7035B restoration
01:06 Inspection and first try
02:42 Disassembly, slide cleaning and platen repair
06:44 A power supply fault?
08:44 X-axis fix
09:30 Y power supply debug and fix
13:07 Y-axis still fails!
13:42 Servo circuits (with elevator music)
18:18 Y servo circuit debug
21:01 It self heals, then self breaks!
22:10 Bad op-amp?
24:55 Root cause, repair, and calibration
28:28 Restoring the pens
32:24 It breaks again!
34:02 Second repair
37:59 Laser L-I curve plot demo