here's my latest pick on FleaBay
Tek Wiki - Photos and schematics
http://w140.com/tekwiki/wiki/DM5120I registred and updated some of the Wiki infos and put a firmware dump there too.
Im gonna hack the meter casing to reduce it in size, but not touch the DM5520 frame who holds it, it's a 3 slot chassis.
The problems are :No direct ac (120-230-240v) supply in it, the small x-former receive from the DM5520 frame a 25v ac for it's primary, gives the +15, -15, -5v dc analog sections.
The main 5vdc 1 amp supply come from the DM5520 frame.
And some small front panel switches with leds who get stuck once in a while. Keithley pn : 260-2454-01 SU-475

( cant find anything on them, obsolete )
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The meter was never repaired or tampled, will do a recap very soon
The analog section has 2 chemical caps and 2 tantalums caps, they will be changed too.
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There's a part called rt1 who intrigues me, you see this part in the Keithley 196 service manual, it goes from the s1 switch thru rt1 to the Q9 and Q16 mosfets ... and the switch goes to U25 "B" pin 7 ??
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I had a Keithley 196 for sale here, but changed my mind, gonna keep it for the meter case hack / mod, mostly the digital section, i wont touch the analog board, but keep it safely.
I dont think i'll keep the DM5520 frame, its a looooong frame (17 inches)
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Eeprom dump of the v1.0 ... attached here, the calibration memory ic is not socketed
Calibration dump in case of ... attached here, your meter may need to be re-calibrated-----------------------------------------
Next photos
The RT1