EEVblog Electronics Community Forum

Products => Test Equipment => Topic started by: MetraCollector on March 26, 2013, 09:10:33 pm

Title: Keithley 2000 issues
Post by: MetraCollector on March 26, 2013, 09:10:33 pm
Hello gentlemen

I bought today Keithley 2000 for about 430$ in local pickup (seller was as young as I am, perhaps he didn't know what he is selling).

Before I turned it on, I looked inside it - nearly burnt 17V zener VR109 - it WORKS at 18.7V and it is really hot.
Then I discovered darker places on the laminate under power components - rectifiers and stabilizers.

My question is - is it normal ? Is there schematic available although it is not provided by Keithley ?
Multimeter works though, but I do not think that heating zener is OK.
I have a bad feeling that some pads were resoldered by someone, perhaps he ran multimeter using 110V voltage selector on our 230V mains.

I would be very grateful for any hints or suggestions.

Thank you and regards Ondrej
Title: Re: Keithley 2000 issues
Post by: nadona on March 27, 2013, 01:26:19 pm
I found this.
http://circuitslab.case.edu/manuals/Keithley_Model_2000_Multimeter_Repair_Manual.pdf (http://circuitslab.case.edu/manuals/Keithley_Model_2000_Multimeter_Repair_Manual.pdf)
Title: Re: Keithley 2000 issues
Post by: free_electron on March 27, 2013, 09:23:57 pm
the first generation of 2000 and 2001 are horrible for this problem...
the diodes blow, the caps leak and explode and eat the traces .....
Title: Re: Keithley 2000 issues
Post by: MetraCollector on March 28, 2013, 01:24:44 am
Thank you, I looked in the repair manual and helped a little. Something strange:  +/-15 rails are at about 15.7V
I can also hear some noise, I am not sure if it is VFD boost converter or something else.

All in all - seller didn't want to discount to half price, he wants multimeter back and my colleague wants his money back. :)
Title: Re: Keithley 2000 issues
Post by: nadona on March 28, 2013, 06:54:40 am
Noise? What noise? I can't hear anything from mine. DMM doesn't make any noise. You'd better return it.
Title: Re: Keithley 2000 issues
Post by: AndyC_772 on March 28, 2013, 07:47:27 am
Yikes!

Is there a recommended mod that I could do to my 2000 to preserve its life? Is it as simple as swapping that diode for one with a higher rating?
Title: Re: Keithley 2000 issues
Post by: cyr on March 28, 2013, 08:57:36 am
I'm pretty sure that area of the board is different on my 2015, which shares the main PCB with model 2000 according to the markings on the board. Perhaps redesigned power supply on later revisions?

My 2001 had one leaking cap when I got it, no major damage. I think that unit was made in 93 or 94, and the one leaking cap was older than the rest and built differently (I think made in 91, others 92/93, all the same series Nichicon).
Title: Re: Keithley 2000 issues
Post by: casinada on March 28, 2013, 04:16:11 pm
You are in Europe, these look like a good bargain:
http://www.ebay.co.uk/sch/i.html?_trksid=p5197.m570.l1313&_nkw=keithley+2015&_sacat=0&_from=R40 (http://www.ebay.co.uk/sch/i.html?_trksid=p5197.m570.l1313&_nkw=keithley+2015&_sacat=0&_from=R40)

 :D
Title: Re: Keithley 2000 issues
Post by: MetraCollector on March 29, 2013, 07:02:48 pm
Thank you, I have already written to Ken for that 2015.

This K2000 is already at his former owner, I will follow local auction system when it appears again. :)
I am pretty sure that he knew about that defects !