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Tektronix DM5120 - a Keitley 196 brother

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coromonadalix:
here's my latest pick on FleaBay

Tek Wiki - Photos and schematics
http://w140.com/tekwiki/wiki/DM5120

I 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
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Next photos

The RT1

coromonadalix:
next photos

Analog boards similarities  196 vs Dm5120

coromonadalix:
next photos


coromonadalix:
next photos  and the 1988 print on the shield

Time travel  loll

coromonadalix:
next photos

You see the massive shield  board and the aluminum cage

The problem is : when you try to remove the top panel section, it is composed of 3 sections slotted together,  the analog section will fall inside the meter,  be careful.

You see the main input pcb adapter,  as i wrote on the first op    You cannot power up the meter directly, it need an 5vdc at 1 amp for the digital section and a 25vac voltage ... for the small xformer inside the meter.


And the second one is the gpib adapter board.

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