[volt-nuts] Keithley 2001 Multimeter Fault

[Alan Scrimgeour]

The little functionality the meter had when I got it enabled me to start a 
self test, but now I can't even do that as functionality has dropped away 
rapidly. The display is fine and presumably the processor driving it, but it 
no longer responds to the keyboard.

A smell of overheating plastic after a few minutes lead me to an LM2940CT - 
5 volt regulator. It's located in the fan assisted cooling path but getting 
far too hot even allowing for that. It's output voltage is well below 5V. 
It's input voltage appeared to be reasonable given it's being overloaded, so 
I conclude that either the LM2940CT is faulty or more likely, something is 
overloading its output. A circuit diagram would show me what connects to 
this output so I can start searching for the culprit.

Alan




----- Original Message ----- 
From: "Laurence Motteram" <LMotteram at scientific-devices.com.au>
To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
Sent: Thursday, March 04, 2010 9:34 PM
Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault


> IP issues aside, what seems to be the trouble with the 2001?
>
>
> Regards,
>
> Laurence Motteram
>
> -----Original Message-----
> From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com] On
> Behalf Of Alan Scrimgeour
> Sent: Friday, 5 March 2010 5:47 AM
> To: Discussion of precise voltage measurement
> Subject: [volt-nuts] Keithley 2001 Multimeter Fault
>
> I'm trying to repair a 7 1/2 digit Keithley Multimeter but can't get the
> circuit diagram. Keithley say they don't release schematics any more due
> to IP issues, whatever they are?
>
> Can anyone help?
>
> Thanks,
>
> Alan
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