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Products => Test Equipment => Topic started by: TiN on January 07, 2014, 04:43:11 am

Title: Keithley 2400 SourceMeter review and teardown
Post by: TiN on January 07, 2014, 04:43:11 am
Followed by my Kei2001 endevaours, i quickly found another level of instruments from this vendor.
SourceMeter series is not just a 6.5 digit DMM, but actually combines three
instruments in one. Keithley have variety of SMUs (http://www.keithley.com/data?asset=5516) for different use requirements.

First is fast and precise 6.5 digit DMM, with ability to measure voltages, currents and resistance.
Second - precision power source, with adjustable compliance levels (limits) for both voltage and current.
Third - given it's four-quadrant power unit, it can not only source but also sink current, acting as active load.

All these functions are synced together and operate using same controls, which making use of it as easy as just normal power supply, but with much higher functional
and precision/accuracy level. These kind units are widely used in semiconductor and production testing and covered from "simple" 20W units like this 2400, to advanced
systems with multiple channels and wide ranges from picoamps to tens of amps. And even base 2400 cost significant money, I got this SMU with broken VFD,
and even then had to pay over 1000$. After salvaging display from trashed Model 2001 and replacing it - unit worked like a charm :)

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5477.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5477.jpg)

Every photo below is clickable to open high-resolution, so enjoy exclusive photo coverage of Keithley Model 2400.
I was trying to find any internal photos on web before, but failed.

Exterior

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5459.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5459.jpg)

It's done in common half-width 19" unit format, just like popular 2000-series DMMs, featuring same bright contrast dot-matrix VFD as Model 2001,2002,7001,7002 has.
Front panel is similar to DMMs, membrane keypad and front inputs. Due to ability of source current/voltage it have button to enable output.

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5460.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5460.jpg)

Rear side have inputs as well, adding guard output and guard sense input. This comes handy to perform unique 6-wire measurements, which is useful when one trying
to source tiny voltages/currents into test device or measuring gigaohms level resistance.
Rest items on this side quite usual, GPIB port, RS232 port, mains IEC power input (have versatile 85-250VAC 50/60Hz input) and digital I/O connector.
Also have Keithley's Trigger link to team with other SourceMeter or measurement instruments for syncronised operation.

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5461.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5461.jpg)

Model 2400 is fanless, so it's producing zero noise, which is nice for home use :D
Left side have massive heatsink to dissipate heat from output stage.

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5462.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5462.jpg)(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5463.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5463.jpg)

My unit was abused by previous owner with some sticky ugly blue liquid which is hard to clean and front panel had few cracks here and there.
Will replace front panel plastic later probably, if it's not too expensive.

So, following Dave's guidance, don't turn it on, tear it apart!

Internals

If you have 2000/2001 DMM and disassembled it, 2400 is no different. Two screws from back, two screws on bottom, and we are in.

(http://dev.xdevs.com/projects/kei2400/repository/raw/schematics/block_diag.png)

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5465.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5465.jpg)

Top board is analog voodoo section, with all sourcing/measuring magic and dozens of expensive Linear Tech, Analog devices opamps, comparators.
ADC is once again using integrating discrete solution, with digital section implemented in ALTERA MAX7160 CPLD.

Under analog board we can find switching power supply and digital brains board. Thanks to SMPS there is no bloody mains switching curcuitry like in Model 2001/2002. :)

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5467.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5467.jpg)

Analog board shielded from digital and SMPS section by another PCB without any components, but only with copper polygons.
That board covers most of analog bottom side and fixed on standoffs:

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5468.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5468.jpg)

Analog voodoo

(http://dev.xdevs.com/projects/kei2400/repository/raw/schematics/analog_diag.png)

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5469.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5469.jpg)

Of course, there is no schematics available, just like with every recent Keithley instrument. Pity, it could be pretty educating to learn thru different solutions
used on this level of instruments.

Output stage

(http://dev.xdevs.com/projects/kei2400/repository/raw/schematics/output_stage.png)

All bottom side of PCB on photo is output stage, which can source power with high precision. All power devices installed on aluminum heatsink
for cooling. During operation that heatsink getting warm, but not hot (+50-55C max), which is just normal for 20W capable unit.

Left corner have optical isolators for communication between digital PCB from below and analog world.

I could not spot voltage reference on this board, it's not using LM399 like Keithley DMMs, but probably use zener or integral reference. There is TP232 test point
just near serial number sticker marked as VREF tho. Its connected from LT1097 opamp output (U226)

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5493.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5493.jpg)

Output stage power source, ZMA Magnetics transformer to provide -225 and 225 voltage source, driven by two transistors on right left.
All output stage section have separation and HV PCB cutouts from rest of analog stuff, nice attention to details.

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5494.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5494.jpg)

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5495.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5495.jpg)

ADC

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5487.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5487.jpg)

Big beefy EPM7160 in PLCC84 package, just like Model 2002. It's configuration have label 2400-801A01. Clock is delivered from FOX 12.000000MHz CMOS generator nearby.
There are two 16-bit DACs, Analog Devices AD7849BR (http://www.analog.com/static/imported-files/data_sheets/AD7849.pdf?) near it, and bunch of opamps.
R609 is TF245 resistor network, which was spotted before in Model 2000 DMM :)

I'll quote service manual here (http://dev.xdevs.com/projects/kei2400/repository/raw/service/Keithley%202400%20Service%20Manual.pdf):

Quote
The SourceMeter unit uses a multi-slope charge balance A/D converter with a single-slope rundown. The converter is controlled by gate array U610. Commands are issued by the MPU on
the digital board through communications opto-isolators to U610, and U610 sends A/D reading data back through opto-isolators to the digital board for calibration and processing.

Rest of analog board photos:

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5488.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5488.jpg)

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5489.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5489.jpg)

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5490.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5490.jpg)

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5491.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5491.jpg)

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5492.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5492.jpg)

Digital side board:

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5466.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5466.jpg)

(http://dev.xdevs.com/projects/kei2400/repository/raw/schematics/digital_diag.png)

Service manual (http://dev.xdevs.com/projects/kei2400/repository/raw/service/Keithley%202400%20Service%20Manual.pdf) again:

Quote
The core digital circuitry uses a Motorola 68332 microcontroller running at 16.78MHz.
The memory configuration includes:

2 x two 256Kx8-bit EEPROMS
2 x 128Kx8-bit RAMs

They are used in parallel to utilize the 16-bit data bus of the MPU. The RAM is battery backed-up, providing
continued storage of data buffer information during power-down cycles.
All calibration constants and system setups are stored in a separate serial EEPROM.

So we are safe here and 2400 will not brick itself when battery go bad after dozen of years.

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5471.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5471.jpg)

No much component magic here, it's similar to other Keithley products of that era.

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5473.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5473.jpg)

Some LDO power for digital domain.

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5474.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5474.jpg)

Another SMPS with ZMA Magnetics transformer.

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5470.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5470.jpg)

Battery for RAM and two configuration jumpers. Based on silkscreen labeling, same digital board is used for both Model 2400 and Model 2410 SMUs (2410 can source up to 1100V)

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5475.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5475.jpg)

Interesting find - PCB capacitors (?). Maybe it's used to read mains frequency due to AC coupling, but that's really just my guess :) Would be interesting to know
what are those square pads connected to mains input actually do :)

Mains power supply

Not much interesting here, it's KTH-7063 model power supply, probably made by some OEM for Keithley.

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5485.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5485.jpg)

Voltage output is 5V 1A and +12V 2.9A.

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5486.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5486.jpg)

And, front panel

Membrane keypad with rubber keys, just like good old 200x DMM series.

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5478.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5478.jpg)

This is how i got it, VFD glass broken, magic vacuum is gone.

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5479.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5479.jpg)

Back side.

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5480.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5480.jpg)

Desoldered VFD, using solder wack to suck all solder. Thanks to little bigger pads, i could manage to free display from PCB relatively easy.
I had one of 2001's with lots of components missing, so used VFD from it. New VFD ready prior to soldering:

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5481.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5481.jpg)

There is minor difference - 2001 VFD had straight row of pins, while 2400 PCB had checker formed pins. Had to do some creative forming to solder new one on 2400 PCB :)

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5482.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5482.jpg)

All done, exploded view of all parts before assembly:

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5483.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5483.jpg)

Assembled, first power on:

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5500.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5500.jpg)

It works! I already updated firmware to C21, downloaded from Keithley website.

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5502.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5502.jpg)

Last cal was 13 september 2007, which is recent, compared my 2001's 1993 and 1995 years, haha.

Some simple checks, 87V and my first 2001 measuring 1.23455V output from 2400.

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5515.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5515.jpg)

2V output:

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5519.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5519.jpg)

210V output:

(http://dev.xdevs.com/projects/kei2400/repository/raw/photos/small/_TIM5521.jpg) (http://dev.xdevs.com/projects/kei2400/repository/raw/photos/_TIM5521.jpg)

Hope you enjoyed reading :)
If anybody have idea what to try or show more on this SourceMeter, feel free to shoot :)

I think volt-nut horde got one more follower, just ordered today bunch of Linear tech opamps, couple DAC and ADCs and first LTZ1000A...
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: chickenHeadKnob on January 07, 2014, 05:13:24 am
@TiN: Thank you for so thoughtfully documenting your efforts.
 I am going to read it multiple times. In many respects a teardown of an old Keithley is more relevant to us than robrenz new SMU as most of us won't buy one of those and the used market is nill for the same. One thing that disturbs me about Keithleys, they do seem to get sick and die a lot, at least much more than the equivalent HP/Agilent. That might just be a false impression as the repaired units get talked about on the EEvblog and working units don't. Looking at all the  "my 2000x  multimeter ist borken" threads I imagine the ratio of living to dead Keithleys is inverse to that of HP3440x which appear to be tanks.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TiN on January 07, 2014, 05:40:43 am
I'd like to see teardown of 2450 either, but we got what we got here :)

As for repairs, i think it's wrong impression, maybe because of age of those units.
So far i did not found on web anybody saying about faulty keithley's earlier than 2005 year or so.

I bought myself 7 2001's (5 dated 1992, 2 dated 1994) and this 2400 and two 7001's.
And all this was possible only because i bought them all broken and did not mind to take risk
of fixing them :)
2001 did have issue with voltage drive circuitry in old units, which was fixed on later ones.
None of instuments of 20 year old age safe from caps bulging and leakage either. And broken VFD in this case?
Can happen to any meter, and I still prefer VFD over anything else for usability reasons.
Hell, even space satellites fail :)

But i think positive side - due to age and abuses from owners, normal hobbyists (almost like me, lol) can buy
broken precision instruments, spend some time fixing them up, and get a handy and highly useful tool for
almost any kind of use. As everyone starting in EE, i had choice to buy some cheap bench meters and sources,
from rigol or other brands (which still do job in most of cases) or get some not so fancy but reliable and trusty
tools which i can just use, not worry about knobs and fancy menus? Well, i voted my bucks on Keithley (https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm), Tek (https://www.eevblog.com/forum/testgear/tek-csa7404-repair-project/) and HP (http://dev.xdevs.com/projects/hp33120a) years ago already.
Did not regret a second still by today.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: chickenHeadKnob on January 07, 2014, 06:01:49 am

As for repairs, i think it's wrong impression, maybe because of age of those units.
So far i did not found on web anybody saying about faulty keithley's earlier than 2005 year or so.

I bought myself 7 2001's (5 dated 1992, 2 dated 1994) and this 2400 and two 7001's.
And all this was possible only because i bought them all broken and did not mind to take risk
of fixing them :)
...rest elided


 I know,  the image of your stacked "keithley reserve cache" is what gives me the wrong idea, I am a visual animal. Even if Keithleys are less reliable, like a high maintenance girlfriend that can still be fun.

As far as the picture of those square capacitor pads purpose - I am thinking isolated zero cross detect.



Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TiN on January 07, 2014, 06:16:30 am
What I meant, is fact of having bunch of dead keithleys in one hands and couple repair threads on popular forum does not mean that they are more or less reliable.
Maybe that person just a zombie addict and was looking for dead meters on purpose, for collection. I got couple dead HP gear too, 33120 and now 4263B (just arrive today, still in post office),
but it says nothing about reliability. That's it, back to topic :)

Yes, that's what i thought about zero-cross or frequency readout as well, as that's all my knowledge in analog stuff can cover for, as for today  :-//

Actually this 2400 already on my desk for a while, almost a year, use it on almost daily basis. Very handy for curcuit probing, as current/voltage levels can be set flexible.
Assembled small buzzer with NFET for one of digital outputs, and setup it to buzz on compliance FAIL condition, so turned 2400 into simple diode-check buzzer  :-DD

Only difference that current and voltage levels can be set accurately, so i can easy distinguish dead short from 1 ohm resistor, for example.
Also useful to test current sources and zeners. Just connect zener, source voltage mode, set compliance current to 10mA and you see zener voltage on screen right away.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: robrenz on January 07, 2014, 12:32:21 pm
Very, very, nice teardown and review  :clap: :clap:  Excellent pictures and content. :-+

I wont be tearing down my 2450 any time soon.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: free_electron on January 07, 2014, 02:48:59 pm
Drool... I always wanted a smu but they are so bloody expensive. At 1000$ this was a steal !

As for bad keithley threads.
Keithley had massive problems with ther 2001 2002 machines due to leaky capacitors eating traces on the pcb. This was solved in later revisions.

Agilent then has certain machines that all die because of leaking backup batteries . The 8112 or 8116 are notorious. So is the 34970a...

Everybody has a few black sheep

The agilent 346x supplies frequently fry theor a/d logic and analog. This is because of a spike on the 15 and -15 rail at powerup ..
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TopLoser on January 07, 2014, 03:07:43 pm
Drool... I always wanted a smu but they are so bloody expensive.

Couple of new in box ones cheap if you fancy one  ;)

Keithley 2636A dual channel sourcemeter
http://uk.rs-online.com/web/p/bench-power-supplies/7588881/ (http://uk.rs-online.com/web/p/bench-power-supplies/7588881/)
Boxed, unused, with all unopened accessories and manuals. Calibrated a few months ago.
List price £10,200+VAT, I'm asking £4,500+VAT (no VAT outside EU)

Keithley 2410
http://uk.farnell.com/keithley/2410/meter-sourcemeter-1100v/dp/2074738?Ntt=keithley+2410 (http://uk.farnell.com/keithley/2410/meter-sourcemeter-1100v/dp/2074738?Ntt=keithley+2410)
Boxed, repaired, meter only. Calibrated by Keithley last month. Looks perfect, my guess it was bought and returned - cheap equipment hire.
List price £4,800+VAT, I'm asking £2,100+VAT (no VAT outside EU)

Free shipping worldwide on either item.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: free_electron on January 07, 2014, 03:26:44 pm
For 500$ maybe. A ything above that is no-go
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: Carrington on January 07, 2014, 04:15:47 pm
@ TiN: I love it, and the images are stunning.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: uoficowboy on January 09, 2014, 05:05:12 am
Output stage

(http://dev.xdevs.com/projects/kei2400/repository/raw/schematics/output_stage.png)
Anybody care to venture an explanation as to how this power stage works? I've never seen anything like it!
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: SeanB on January 09, 2014, 06:00:51 am
It is designed to reduce dissipation in the devices, as the output voltage rises various devices turn on and off so as to use the various supply rails so as to not dissipate high power at low voltage output. The mosfets are held off until the output is close to the supply rail for the section then they start turning on and then the diodes block current from flowing back into the various supplies.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: EEVblog on January 09, 2014, 06:12:53 am
Awesome work on the teardown and photos.
I so want one of these, or more precisely (pun intended), the newer model.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: EEVblog on January 09, 2014, 06:14:27 am
It is designed to reduce dissipation in the devices, as the output voltage rises various devices turn on and off so as to use the various supply rails so as to not dissipate high power at low voltage output. The mosfets are held off until the output is close to the supply rail for the section then they start turning on and then the diodes block current from flowing back into the various supplies.

I recall Doug Ford explaining to me once how he used something similar in his Jands audio amp designs.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: nowlan on January 09, 2014, 06:29:19 am
Sounds like Class-G amplifier.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TiN on January 22, 2014, 05:02:19 am
Seems this story have a happy ending after all :)

Got my unit calibrated by official Tek/Kei service.

Data before calibration (http://dev.xdevs.com/attachments/download/815/2400-0788393%20as%20found.pdf)
Data after calibration (http://dev.xdevs.com/attachments/download/816/2400-0788393%20as%20returned.pdf)

So this will become a reference point/source from now on on my volt-nutting explorations.  :bullshit:

Btw, if anyone want - there is an broken 2400LV (no 200V range) poped up on bay recently: eBay auction: #201021188476.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: robrenz on January 22, 2014, 12:26:38 pm
Nice!  :-+
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TiN on February 05, 2014, 01:50:18 am
Just got my bad boy back :)
Now have some reference point for volt-nut practice.

(http://dev.xdevs.com/attachments/830/kei2400.jpg)

Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TiN on March 06, 2014, 01:37:05 pm
2400LV for 750$ with faulty output :)
http://www.ebay.com/itm/Keithley-2400-LV-Sourcemeter-/201046424972 (http://www.ebay.com/itm/Keithley-2400-LV-Sourcemeter-/201046424972)
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TiN on July 08, 2015, 04:25:27 pm
Yey, Keithley still cares about 20 year old models...

New firmware released recently, in case someone with 2400 series SMU from Japan need it.
Why Japan?

Release notes:

Version C33 fixes the issue of powering up with a low line-voltage (90 volts in Japan) for models 2420, 2425, 2430, 2440. Upgrading to this version of firmware will add a 5-second delay to power-up for all models running it.

Models affected: 2400, 2400-C, 2410, 2410-C, 2420, 2420-C, 2425, 2425-C, 2430, 2430-C, 2440, 2440-C
Symptom: The instrument will power up, but the digital circuitry will not work properly. Therefore, there is voltage on the output and no readings are accurate.
Resolution: The issue has been corrected.
Enhancements: There were no enhancements included in this release.

Remirrored it on on docsite (http://doc.xdevs.com/article/keithley-instruments/#2400), as usual, in case you don't want login into Keithley's site.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: rksaripalli on September 11, 2015, 05:41:08 am
Dear Sir/Madam,

Myself Ravi Kiran Saripalli, PhD student in India. I have read the excellent review article by Tin regarding Keithley 2400 Source meter. I have been using the source meter regularly for poling my dielectric materials, by applying a voltage, and varying the temperature externally. I had heated my sample to 380K and connected the leads to the 2400, and just when I was about to increase the voltage, the 2400 just switched off, and is not powering on again (Input volate was 0V). Could you tell me what could have gone wrong and how to fix it? Thanks a lot.
Ragrads,
rksaripalli
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TiN on September 11, 2015, 02:04:26 pm
Hi Ravi,

Did you check mains fuse on unit? Voltage was applied to your test sample by 2400 itself or from other source?
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: K. Kumon on November 27, 2015, 09:56:29 pm
Why Japan?

 (I'm living in Japan. :))

By the way, I recently obtained used 2400

The source part (voltage and current) seems OK with tens milli volt offset voltage.
But measurement part doesn't work at all.

The display always shows "-----" for both voltage and current.
When sampling rate is changed with config menu causes complete deadlock.
All button reply no response except power SW.

It seems as if sampling trigger is missing.

Does somebody kindly advice me how to fix it?
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TiN on November 29, 2015, 10:51:46 am
What happens if you reset SMU to factory defaults? It should be reading values without any extra settings.
Perhaps stupid question, but does ON light come up when you enable output?

Take the cover off meter amd check if any cables or parts are damaged.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: K. Kumon on November 30, 2015, 02:00:27 am
What happens if you reset SMU to factory defaults? It should be reading values without any extra settings.
Perhaps stupid question, but does ON light come up when you enable output?

Take the cover off meter amd check if any cables or parts are damaged.
Hi, TiN,

Thanks for suggestion.

I did resetting to the factory default, but nothing has changed.
As the output on/off button pushing, LED (blue) is lit and output voltage comes up

The apparent of the unit is rather good condition, and VFD is still bright.
For this reason,  I've been hesitating to open, but I'm going to open it.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TiN on March 01, 2016, 02:45:44 pm
Revive, revive...

(https://xdevs.com/doc/Keithley/2400/calsw/screen_dbg.png)

Time to recalibrate my SMU. To do so in correct way, worth to spend some python-spaghetti-coding for calibration app for 2400 + 3458A.
So far both instruments talking well, ironing bugs..

Once done, it will be posted as usual  :-DMM
Not sure if anyone need this :)
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: ManateeMafia on March 01, 2016, 02:58:58 pm
Hmmm, sounds like a good idea. :-+
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TiN on March 01, 2016, 04:51:35 pm
Okay, first beta sorta works.
Verification readings are not correct, but calibration is ok.

(http://doc.xdevs.com/doc/Keithley/2400/calsw/_LAB6918_1.jpg) (https://xdevs.com/fix/kei2400/#diycal)

Usage is simple.

On execution it will check for GPIB:3 = HP3458A ID and GPIB:24: KI 2400 ID.
If ID matches , it will save current calibration constants of 2400 into txt file.
Then user required to connect 2400's HI/LO to DMM HI/LO.
DMM will be ACAL ALL and then DCV calibration will execute.
2400 will beep when change to current input at DMM will be needed.

Python app for Raspberry Pi + 3458A + KI2400 (http://doc.xdevs.com/doc/Keithley/2400/calsw/cal2400.py)

Calibration log TXT data (http://doc.xdevs.com/doc/Keithley/2400/calsw/callog_test.txt)
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: z01z on April 19, 2016, 09:20:33 am
@TiN

After seeing your teardown, I am wondering about the infamous caps. Isn't it advisable to replace the electrolytic caps here, too?

If it is not too much trouble, would you be so kind as to capture the output of your 2400 with a scope? If possible both with light (20V, 100kOhm) and heavy load (20V, 20Ohm), or whatever load resistor you have handy. I'd like to compare your results with the device I have access to, to see whether it works well or not.

Thank you in advance!
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: plesa on April 23, 2016, 08:28:20 am
Just bought Keithley 2410 for $300 for parts. It seems to have issues in source part.
Thanks TiN for calibration script, it will be handy after repair.
I expect some damaged transistor in source section and zener diodes. Display is quite dim, another 7001 will be harvested:)
Unit is made in 2008 and hac C27 firmware.
Pictures will follow soon.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TiN on April 23, 2016, 08:33:57 am
You filthy man :) I was watching that one. Well, sorta. Hopefully it's just a broken FET. Full teardown is expected, counting on ya ;)
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: plesa on April 23, 2016, 09:55:35 am
I cannot resist to buy it for parts and try repair it. Faulty 2600 series is still too expensive and 2400 is fanless, which is big advantage.
It must be some kind of addiction:)
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TiN on April 23, 2016, 10:12:56 am
Well you can break yours working ones and then u will have parts :D

Careful with 2410, it have 1.2kV on top end rails.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: plesa on April 23, 2016, 10:52:01 am
Because you know how you damaged it it is less fun:)  With buying meter with unknown state it is more troubleshooting from scratch. Thats more fun I suppose.
Yep,  I will use the experience from K6517A repair. I expect they are using same Sanyo 2SK1412 transistors and one or more will be dead and this will also damage components close to them.

BTW another K6517A electrometer is waiting for repair, but It is more challenging, it did not fall down from rack like first one ( broken VFD), but it has blown input stage by overvoltage spike.
There is input protection (few series resistors and LS313 ( dual NPN ) and input stage is made by LMC6001. I found one faulty 2N3904 transistor but nothing else yet.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: HighVoltage on April 23, 2016, 11:56:44 am
Hello TiN,

I have the 2420-C 3A version of this SourceMeter
Will your calibration script maybe work on this one as well?

Really nice work you do.
Thanks.

Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TiN on April 23, 2016, 12:06:05 pm
Lol, you guys were waiting all this time to hop in? :)

Here is the idea for you all. How about all of us make a comparison of 24xx series, in terms of output stages and perf? Making python app to support all 24xx's should be easy enough. I can do that, also supporting different DMMs (perhaps K2001/2002, 34470,3458, etc.)

Could be good article on SMU design practicality out of this.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: HighVoltage on April 23, 2016, 12:31:27 pm
Please include the 2420-C in combination with the Keysight 34470A
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TiN on April 23, 2016, 12:53:04 pm
Well, I'll include, but all the testing and tweaking will be your job to do, as I have none of HP meters except 58.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: etrash2000 on May 14, 2016, 11:28:38 am
Just bought Keithley 2410 for $300 for parts. It seems to have issues in source part.
Thanks TiN for calibration script, it will be handy after repair.
I expect some damaged transistor in source section and zener diodes. Display is quite dim, another 7001 will be harvested:)
Unit is made in 2008 and hac C27 firmware.
Pictures will follow soon.

Did you ever got to work?

If not, would you like to sell me the EEPROM. I have a functioning but bricked 2400. I dont have the equipment to re-flash the EEPROMs so I would like to buy the EEPROMs.

If anyone is interessted to sell these 2400-803 and 2400-804 EEPROM then please contact me at etrash2000@yahoo.se

Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: plesa on May 14, 2016, 07:46:42 pm
Just bought Keithley 2410 for $300 for parts. It seems to have issues in source part.
Thanks TiN for calibration script, it will be handy after repair.
I expect some damaged transistor in source section and zener diodes. Display is quite dim, another 7001 will be harvested:)
Unit is made in 2008 and hac C27 firmware.
Pictures will follow soon.

Did you ever got to work?

If not, would you like to sell me the EEPROM. I have a functioning but bricked 2400. I dont have the equipment to re-flash the EEPROMs so I would like to buy the EEPROMs.

If anyone is interessted to sell these 2400-803 and 2400-804 EEPROM then please contact me at etrash2000@yahoo.se
Not yet, but in progress. I can made image or program chip with C32 (C33 has few second delay on startup).
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TiN on May 15, 2016, 05:30:37 am
Give man a fish, he will be fed for one day.
Give man a net, he will be fed forever :)

etrash2000, I'd suggest to get USB programmer with adapters, such as TL866 (http://www.ebay.com/itm/TL866CS-Mini-High-Speed-USB-Universal-Programmer-With-9-pcs-Adapters-/310830846162?hash=item485ef650d2:g:-tEAAOSwl8NVZsGB) and some 2MBit Flash chips (e.g. Digikey's SST39SF020A (http://www.digikey.com/product-detail/en/microchip-technology/SST39SF020A-70-4C-NHE/SST39SF020A-70-4C-NHE-ND/2297830).). This will make you almost never worry again about programming ICs.
I used TL866 myself on most of my repairs, it covered it's cost manyfold already.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: etrash2000 on May 15, 2016, 06:48:21 pm
Give man a fish, he will be fed for one day.
Give man a net, he will be fed forever :)

etrash2000, I'd suggest to get USB programmer with adapters, such as TL866 (http://www.ebay.com/itm/TL866CS-Mini-High-Speed-USB-Universal-Programmer-With-9-pcs-Adapters-/310830846162?hash=item485ef650d2:g:-tEAAOSwl8NVZsGB) and some 2MBit Flash chips (e.g. Digikey's SST39SF020A (http://www.digikey.com/product-detail/en/microchip-technology/SST39SF020A-70-4C-NHE/SST39SF020A-70-4C-NHE-ND/2297830).). This will make you almost never worry again about programming ICs.
I used TL866 myself on most of my repairs, it covered it's cost manyfold already.

Thanks TIN, I think I will buy the TL886A and the memories as they were dirt cheap.
Do any of you have the memory map for the 2400, for example, were are the device serial number and calibration values stored?
Is there anything I should worry about or be careful with?
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: plesa on May 15, 2016, 07:28:32 pm
Yep, buy TL866A with ICSP port. The calibration should be stored in U17 (24LC16B) including serial number and calibration dates.
When you have programmer connect ICSP and make backup.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: etrash2000 on May 17, 2016, 08:13:32 pm
The TL886A is now ordered so I should have the parts in 1-3 month from china.  :=\

I also checked the original memory in the 2400 just in case anyone else is interested in this subject, it was a AM28F020-120JC (with date code 9811).
TIN/Plesa, do you know if I can use a 8M/4Mb memory instead of the 2Mb, would it benefit the equipment in any way or am I forced to use the same size as the old memory.

Regards
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: z01z on May 18, 2016, 06:54:15 am
do you know if I can use a 8M/4Mb memory instead of the 2Mb, would it benefit the equipment in any way or am I forced to use the same size as the old memory.
No benefits, only hassle.
It can work if you only want to manually program the memory. You'll have to check how the extra address pin(s) are connected though. If you'd simply put the same data to the extra memory areas, only the unconnected pin might cause a problem.
If you're planning to use Keithley's flash programmer program however, the chances are it won't like it. For that matter, the same might be true for any random replacement. I remember seeing a list of different types (probably those are supported by the program), either in a txt or in the exe itself. It's better to choose one that is supported.

Edit: In fact there's a flshdata.txt file, the following are supported by the flash wizard. TiN's suggestion is included, so that should be fine.
Code: [Select]
' Number of Flash Parts Supported
47
' AMD29F040 (+5V, 4M)
&H1A4&,&H1A4&
' AMD29F002NB (+5V, 2M, Bottom Boot)
&H134&,&H134&
' AMD29F002NT (+5V, 2M, Top Boot)
&H1B0&,&H1B0&
' IS28F020 (+5V&+12V, 2M, Single Sector)
&HD5BD&,&HD5BD&
' AMD28F020A (+5V&+12V, 2M, Single Sector, Embedded Programming)
&H129&,&H129&
' AMD28F020 (+5V&+12V, 2M, Single Sector)
&H12A&,&H12A&
' M28F201 (+5V&+12V, 2M, Single Sector)
&H20F4&,&H2011&
' M28F201A (+5V&+12V, 2M, Single Sector, Embedded Programming)
&H20F5&,&H2012&
' SST28SF040 (+5V, 4M, 256byte page erase, byte write)
&HBF04&,&HBF04&
' SST29EE020 (+5V, 1M, 128byte pages)
&HBF10&,&HBF10&
' SST39SF040 (???????????????????? it's a new chip)
&HBFB7&,&H1F0B&
' SST39SF020A
&HBFB6&,&H1F0B&
'MX29F040C (+5, 4M)
&HC2A4&,&H1F0B&
' W29C020 (WinBond, +5V, 2M, 128byte pages)
&HDA45&,&HDA45&
' TMS28F020 (+5V&+12V, 2M, Single Sector)
&H89BD&,&H89BD&
' ATMEL29C020 (+5V, 2M, 256byte pages)
&H1FDA&,&H1FDA&
' ATMEL49F020 (+5V, 2M, Bottom Boot)
&H1F0B&,&H1F0B&
' ATMEL49F002T (+5V, 2M, Top Boot)
&H1F08&,&H1F08&
' ATMEL49F040 (+5V, 4M, 8 sectors)
&H1F13&,&H1F13&
' CAT28F020 (+5V&+12V, 2M, Single Sector)
&H31BD&,&H31BD&
' W49F002B (+5V, 2M, Bottom Boot) -> AMD29F002NB
&HDA25&,&H134&   
' W49F002N (+5V, 2M, Top Boot) -> AMD29F002NT
&HDA0B&,&H1B0&
' W29C040 (+5V, 4M, 256byte pages) -> ATMEL29C020
&HDA46&,&H1FDA&
' BM29F040 (Bright Micro Elec/Winbond, +5V, 4M, 8 sectors) -> AMD29F040
&HAD40&,&H1A4&
' M29F040 (ST, +5V, 4M, 8 sectors) -> AMD29F040
&H20E2&,&H1A4&
' M29F0002NT (+5V, 2M, Top Boot) -> AMD29F002NT
&H20B0&,&H1B0&
' SST27SF020-70/90-3C-NH (+5V&+12V, 2M, Single Sector) -> TMS28F020
&HBFA6&,&H89BD&
' SST29EE020A (+5V, 1M, 128byte pages) -> SST29EE020
&HBF24&,&HBF10&
' V29C51002B-55J/90J (Mosel, +5V, 2M, Bottom Boot) -> AMD29F002NB
&H40A2&,&H134&
' V29C51002T (+5V, 2M, Top Boot) -> AMD29F002NT
&H4002&,&H1B0&
' V29C51004B (+5V, 2M, Bottom Boot) -> AMD29F040
&H40A3&,&H1A4&
' V29C51004T (+5V, 2M, Top Boot) -> AMD29F040
&H4003&,&H1A4&
' V29LC51002-90J (Mosel, +5V, 2M, 512byte sectors) -> AMD29F002NB
&H4082&,&H134&
' AS29F040-55LC/70LC/70LI/90LC/90LI (Alliance Semi, +5V, 4M) -> AMD29F040
&H52A4&,&H1A4&
' HY29F040AC-55/55I/70/70I/90/90I/12/12I (Hyundai, +5V, 4M) -> AMD29F040
&HADA4&,&H1A4&
' TE28F800C3B (Intel, +3.3V, 8Mb, x16, TSOP, 8-8kB + 15-64kB sectors)
&H008988C1&,&H008988C1&
' TE28F160C3B (Intel, +3.3V, 16Mb, x16, TSOP, 8-8kB + 31-64kB sectors)
&H008988C3&,&H008988C3&
' TE28F320C3B (Intel, +3.3V, 32Mb, x16, TSOP, 8-8kB + 63-64kB sectors)
&H008988C5&,&H008988C5&
' Numonyx 28W320FCB -> Intel 28f320C3B
&H002088BB&, &H008988C5&
' TE28F640C3B (Intel, +3.3V, 64Mb, x16, TSOP, 8-8kB + 127-64kB sectors)
&H008988CD&,&H008988CD&
' AMD29F400BB (+5V, 4M, Bottom Boot, x16, TSOP)
&H000122AB&,&H000122AB&
' AMD29F400BT (+5V, 4M, Top Boot, x16, TSOP)
&H00012223&,&H00012223&
' HY29F400BB (+5V, 4M, Bottom Boot, x16, TSOP)
&H00AD22AB&,&H00AD22AB&
' HY29F400BT (+5V, 4M, Top Boot, x16, TSOP)
&H00AD2223&,&H00AD2223&
' ST29F400BB (+5V, 4M, Bottom Boot, x16, TSOP)
&H002000D6&,&H002000D6&
' ST29F400BT (+5V, 4M, Top Boot, x16, TSOP)
&H002000D5&,&H002000D5&
' MX29F400CB -> AMD29F400BB
&H00C222AB&,&H000122AB&
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: etrash2000 on May 18, 2016, 09:45:47 pm
Thanks for the list. I will have look on that.

A question, according to the data-sheets, SST39SF020A is a 5V only device for reading/writing while the original AM28F020 requires 5V for reading and 12V for writing. How can the Keithley 2400 write to the memory since the Vpp is not connected on the SST39SF020A?
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: z01z on May 19, 2016, 08:43:00 am
Well, what surely works is using the same flash as the original. Any other type is a gamble.
Any same sized flash most probably works if programmed externally, I'd still check pin layout and waveforms.
Whether in circuit programming works or not will only turn out if tried, it is only a theory that if the type is supported by the flash wizard, it will be programmed.
What you've notice isn't the only difference, the programming word sequence also differs. It is possible to read manufacturer and device ID from these chips. Based on this info the correct algorithm can be executed, if implemented by the programming bootloader. But again, this is a gamble.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: etrash2000 on June 09, 2016, 09:19:43 pm
A short update for the interested ones.

I manages to save my bricked Keithley 2400 device by using the recommended TL866A programmer with a 4 MBit memory module SST39SF040-70-4C-NHE.
I did the programming directly on the TL886. I did not dare to use ICSP since I did not have clear instruction and the pinout of the Keithley.
The programming step was straight forward and worked on the first try. I used the even+odd C31 firmware supplied by TiN on xDevs.com

The calibration seems to be OK but I will probably do a new calibration of the unit this summer by using the script TiN has written for HP 3458A. 
The next step will be to do a noise analysis of the unit as z01z suggested. Pictures will be up within a few weeks (too much work right now).

So, a big thanks to all and specially TiN for the files and instructions.

Kind regards
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: Colnago on November 23, 2016, 11:52:57 am
2400LV stopped functioning while measuring.
Digital part seems to function to the extent that I could even upgrade the firmware to C33 but still no readings, only '----'.
When switching on output it shows +23,977V when measuring voltage, 0,0003A for current and overflow for resistance. Hardly any change when holding leads together (voltage signs changes, current slightly decreases).
All buttons are functioning, reset to factory defaults, communicates (*IDN?, *TST? etc) through GPIB but no readings.
Keithley have a €1800 flat rate which is outside the budget so any suggestion is more than welcome!
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TiN on November 23, 2016, 12:08:38 pm
Standard, take it apart and check pass transistors on power stage. You can check gate resistance to source/drain first.
If all are ok, then you can measure live voltages, to see if all power rails are ok.
Be careful, there are +220/-220V voltages present, pay attention to correct ground referencing during measurement.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: plesa on November 23, 2016, 06:16:07 pm
I will take picture with infrared camera,  this was helpful during my repair.
If you cannot find bad transistor, desolder transistors and test them within operating conditions.
Firmware recommended is C32, C33 has delay to work properly at 90V in mains :) I needs to downgrade, the startup delay was annoying.

BTW is anyone interested in purchasing new VFD DD-51 for Keithley gear, send me PM.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: z01z on November 25, 2016, 02:59:30 pm
Yes, that startup delay is very annoying, I also went back to C32 because of that. It should be made selectable somehow.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: plesa on December 01, 2016, 09:28:02 pm
Christmass for Keithley gear  :-/O
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: plesa on December 18, 2016, 08:50:12 pm
Time to replace few VFD on various Keithley gear. New VFD are little bit smaller with contacts in one line.
VFD holds on PCB 3M VHB double side tape ( reel 33m/150 EUR).
Contacts are soft and easy to bend. By tweezers I select pins row and later align all in two rows by PCB.
After that started from one side and with tweezers I put each pin into hole by tweezers.
After two hours is repair of K2400 finished ( forgot to connect analog board  - Over temperature )
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: ivonenand on January 02, 2017, 11:38:26 am
Hi guys,
Does anyone know, how the output current sense is implemented in this SMU (or any other for that matter)? The thing is, you need extremely high CMRR, since the output is anywhere in the +-200V range. Second, the SMU offers better than 1uA resolution, so there must be little or no leakage on the amplifier connected to the output shunt. You cannot do that with a standard differential amplifier.

Any ideas on how the amplifier connected to the output shunt is implemented?

Regards,
Ivo
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: VintageNut on January 02, 2017, 10:36:00 pm
Hi guys,
Does anyone know, how the output current sense is implemented in this SMU (or any other for that matter)? The thing is, you need extremely high CMRR, since the output is anywhere in the +-200V range. Second, the SMU offers better than 1uA resolution, so there must be little or no leakage on the amplifier connected to the output shunt. You cannot do that with a standard differential amplifier.

Any ideas on how the amplifier connected to the output shunt is implemented?

Regards,
Ivo

I do not have a schematic for the 2400. My assumption is that the 2400 is not far from the 238 as far as architecture. The 238 schematic exists as a printed document.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: plesa on January 02, 2017, 10:53:53 pm
Hi guys,
Does anyone know, how the output current sense is implemented in this SMU (or any other for that matter)? The thing is, you need extremely high CMRR, since the output is anywhere in the +-200V range. Second, the SMU offers better than 1uA resolution, so there must be little or no leakage on the amplifier connected to the output shunt. You cannot do that with a standard differential amplifier.

Any ideas on how the amplifier connected to the output shunt is implemented?

Regards,
Ivo

Check this thread, where is link for schematic of one of Keithley SMU.
https://www.eevblog.com/forum/testgear/keitley-236-teardown-and-review/ (https://www.eevblog.com/forum/testgear/keitley-236-teardown-and-review/)
2400 is quite similar ( at least output stage, which use the same transistors.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: plesa on March 12, 2017, 04:30:08 pm
Unbelievable repair  :)
https://www.youtube.com/watch?v=cZjcL5suh8k (https://www.youtube.com/watch?v=cZjcL5suh8k)
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: julian1 on March 12, 2017, 09:39:38 pm
I did a repair on a 2420 which had burnt power mosfets driving a secondary DC-DC SMPS. The interesting difference with the 2400, is that the power-board and digital board are combined. In contrast, the 2400 uses a third-party non-Keithley power board.

The same pcb is used for the 2430 as well (the silkscreen has a tickbox)- and possibly other high-current output models. Here's a pic of the board,

(http://blog.julian1.io/public/images/2420/DSC02801.JPG)
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: z01z on March 13, 2017, 09:29:33 am
Unbelievable repair  :)
https://www.youtube.com/watch?v=cZjcL5suh8k (https://www.youtube.com/watch?v=cZjcL5suh8k)
It is :)
Then bumped into a video on youtube from TiN's (https://www.youtube.com/watch?v=Z9Jpma6EyZE), about a secret menu in K2400.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TheSteve on August 05, 2017, 05:52:12 am
Used TiN's script to calibrate a 2400 from a 3458A - worked fine but I did make one change so it didn't turn my screen background to yellow during the DCV calibration.
Changed sys.stdout.write ("\033[0;43m*") to sys.stdout.write ("\033[0;40m*") to maintain a black background.


Thank you TiN for the script!
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: TiN on August 05, 2017, 07:26:48 am
Proper would be \033[0;49m ANSI escape sequence, this means default background color.
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: eeviking on November 14, 2017, 05:17:57 pm
Hi
I just scored a Keithley 2400 with a vague "powers off randomly" fault description. It was pulled from a test rack, so was probably running hot for years.
From the description I would suspect bad caps in the psu. Haven't seen the problem yet, but only did some quick tests.
Top board looks clean, haven't torn it down to look at the bottom psu boards yet. It's from around 2001 so a year younger than TiN's.
Question is: Should I just replace all caps?
Anything to look out for? What will be lost if the battery is removed?
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: Jens01 on May 15, 2019, 05:53:41 pm
As an addition to the information already shared here on the forum, here my $0.20.

Bought an defect 2400, bought as broken/for parts. Unit came from a automated test set-up so visually in good condition. Symptoms:
- -240V on banana jacks when output was disabled
- When enabled, the current reading was always off by 9.8mA. When sourcing 9.8mA, the current measured with the output shorted with a DMM in current range was zero. The leaking current was independent of the selected current range.
- The voltage reading was always wrong. Also, when sourcing 50V, the output went up to +240V.

There are quitte some usable test pads on the board. My 2400 differs quite a bit from the photo's from TiN, but here are some hints based on the testpoint labels on TiNs 2400:
- TP201 'NVDAC' and TP203 'NIDAC' referenced against FCOM: respectively DAC voltage and current setpoint. Range dependent, but should linear change when giving a new setpoint.
- TP214 ' EAMP' referenced against FCOM: difference of voltage between pin 2 and 3 of U500. Zero volt means that the setpoint voltage matches the feedback voltage, indicating that the amplifier stage is probably working OK. When reading other than zero volt: output stage clips or is defect.
- TP221 '+si' referenced to TP222 '-si': feedback current. Range dependent, should linear rise with measured output current.
- TP227 '+sv' referenced to TP228 '-sv' feedback voltage. Rang dependent, should linear rise with measured output voltage.

I started with reverse-engineering the output stage, as they seem to fail very often and reverse engineering is easily done as the components are mostly on the top side. The list of designators in K2400 service manual did not match the numbers on the PCB, but it did match with the designator list in the K2410 service manual. Obviously the high-voltage part will differ, but the < 30V part seemed to match well.

Eventually i found out that my unit had a fully working output stage. if i knew about that EAMP testpad before i started.. :palm:
The setpoint dacs seemed to work so the feedback path was the next step to debug. The current feedback path is located near the blue resistor on the front side of the PCB and the voltage feedback path is located next to the black relay on the right side.

 
(https://www.eevblog.com/forum/testgear/keithley-2400-sourcemeter-review-and-teardown/?action=dlattach;attach=736998;image)

This component, Q233 on TiNs photo, became very hot when driving the output to a high voltage. As the voltage reading was always wrong, i eventually found out that op-amp U219 (OPA124) had a large voltage difference between the inverting and non-inverting input. As this op-amp is a simple high-impedance voltage follower, i tested it out of circuit to make sure the output was not externally clamped. With success, the output was stuck at -15V :)

Replaced the opamp and now she's fine again.

Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: Kjelt on May 15, 2019, 09:05:01 pm
Bought an defect 2400, bought as broken/for parts. Unit came from a automated test set-up so visually in good condition.
Troostwijk solar factory auction ? Missed those, the prices skyrocketed  :(
Title: Re: Keithley 2400 SourceMeter review and teardown
Post by: Jens01 on May 16, 2019, 05:40:36 pm
Bought an defect 2400, bought as broken/for parts. Unit came from a automated test set-up so visually in good condition.
Troostwijk solar factory auction ? Missed those, the prices skyrocketed  :(

No, Ebay. The name 'Keithley' was misspelled, so i was just lucky to be at the right time at the right place. ;)