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Keithley 2400 SourceMeter review and teardown

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openloop:

--- Quote ---U660 AD7849 is hot and not changing the current setting.
--- End quote ---

U660 is voltage (not current) control.

Although fried DAC would explain observables nicely.

kawal:
Yes U660 is removed and the situation is not changed apart from NVdac showing +12V everything else looks the same :palm:
TP213 was -0.75V
Getting expensive

Either way why is there -240V on the output when teh output is not enbaled.

openloop:

--- Quote ---U660 is removed
--- End quote ---

Don't rush into things.  :)

TP213 (THE control) can be driven down either by voltage drive: TP205 near U211 (not TP206!) OR by current drive: TP207 (near U213)

Please check those voltages. (to figure out is it current control that screws things up or is it voltage control)

kawal:
TP205 = 0.566V
TP207 = -7.4V
Openloop
Do you have a schematic of this unit ?

openloop:

--- Quote ---Do you have a schematic of this unit ?
--- End quote ---

Nope, just bad experience.  ;D


--- Quote ---TP207 = -7.4V
--- End quote ---

So the current control is bad...

Let's check the summing point where feedback is added to (current) DAC's output:

R238 pin 1: DAC
R238 pin 2: DAC + feedback
R238 pin 3: feedback

What are the voltages on those pins?

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