First time on Keithley 2000

[Nuno_pt]

The prices are from Farnell when I order them, today the 1829978 is showing 1.89€ + VAT each.

The prices that I put was for 2 units of each + VAT, the final price was 18.66€ with VAT  for the order

[Kjelt]

Ok thanks, our dutch Farnell is probably a bit more expensive 

[Kjelt]

Last question, I am looking through the list you provided but they are not all Panasonic like you ordered, some are Rubycon, you changed your mind or why?

[Nuno_pt]

Kjelt, I choose that because it was what the dealer from Farnell was having here on stock, so instead of waiting three days for the order to came directly from Farnell.es, I choose the Rubycon, very concept brand of Electrolytics.
It was only more convenient that way, and also the Rubycon that I choose have more hours at 105C then the Panasonic ones, so all for all I choose more hours at 105C or 125C, the rest are the same, Voltage and +-20%.

[dramoto]

Please....
When you have price in Portugal for calibration, share it hier.
I don't find a cheap option for calibration in Spain for hobby purpose.

After this maybe start looking for a Cal lab here in Portugal to send the meter to Calibration and upgrade to A20 firmware.

[Nuno_pt]

Today I got some free time and change the electrolytic caps, all work well, but some careful is needed when de-solder the age caps, like TiN already said in other Keithley treads, the place where the caps are solder are very thin, so they will peal of if you put to much heat on them, this are not polygons, just a very thin circle of copper, so be very careful here.

After clean all the flux, and then clean the PCB with IPA to remove all the residues.

Pictures will follow soon.

Now just replace the EEPROMS when I'm back from holydays, the TL866CS with the adaptors is already in order, it should arrive in the next 20 days, if it doesn't stop in customs, for the VAT.

Then will see the price of the Calibration price, if it's an acceptable price will upgrade to A20 and send it to the Cal Lab.

Will post here the price of the Calibration price and the webpage of the entity lab.

[Kjelt]

Thanks for the heads up for desoldering. No large groundplanes, then around 300^oC will be needed?

[Nuno_pt]

TiN on some other treads said around 250/260, I was ok with 300/320.

An ZD-985 de-solder station will be very useful to take the caps out, the problem is de-solder them with such small circle of copper.

For me was more trouble to de-solder them without the ZD-985, I was using an manual sucking de-solder, the solder part was easy.

Next follow up will be the EEPROMS.

And maybe next the U136 NVRAM, maybe here burn it with the code of some 2000 in calibration specs, the DMM would be in cal without send it to a Cal Lab.

Pictures link : https://1drv.ms/f/s!Aibdz8jXIGKi3nBBkZ_aGJdciGTp

[Kjelt]

I heard a lot of the 78xx are overheating on the Keithley, perhaps an idea to upgrade them to the new Maruta sm 78xx replacements. I do not let my meters run for more than an hour, i switch them on /off when needed just like a multimeter so no need for upgrading them but if you are a long time user that switches on in the morning, and off in the night it might be an interesting upgrade.

[Kjelt]

Today my caps arrived, those 1000uF/50V are incredibly tall 
Looking at your pictures they are the same. They are twice as high as the original ones, oh well if they fit in the casing and last twice as long I am happy , it is not a portable equipment after all.
Thanks for the list, will do the recapping this weekend.

[Kleinstein]

A linear regulator like the 78xx will dissipate essentially the same amount of heat, not matter what type. So not much to save there. It would be better cooling to reduce the temperature or a modified raw supply (e.g. inductor or resistor in series with rectifier if there is ample voltage) that could help to reduce power dissipation, by lowering the voltage before the regulator.

Such a DMM should be one for something like 1 hour before the readings are really stable. So i't no unusual to even have them running 24/7, when used in a critical application.

[Kjelt]

Today my caps arrived, those 1000uF/50V are incredibly tall 

It looks to me that they do not fit or barely fit, Nuno do you already have the cover replaced , does it fit? 

A linear regulator like the 78xx will dissipate essentially the same amount of heat, not matter what type. So not much to save there.

Those Murata's are 78xx pincompatible SMPS replacements, so a lot to save  But they are not in the 15V available, so no solution in this case.
http://power.murata.com/data/power/dms-78xxsr.pdf 

[Macbeth]

I can't see how those tall 40mm 1000uF caps can fit without squeezing them in and dragging the case on top of them every time its opened & closed. Not to mention just pressing on the cover will end up forcing them against the PCB. Also heat expansion? I wouldn't select any capacitor taller than the large 6800uF which barely leaves a gap and is 35mm high.

Farnell 1973521 fits the 12.5 dia 25mm high dimensions of the original but is only rated 2000 hours at 105C. I think I will take half the life vs much greater risk of mechanical damage

I also have a 2015 with a newer revision board. I notice in the Keithley 2015 Service Manual the same caps (C131, 148) are rated at 2200uF and 35V instead of 1000uF 50V. However the board has room for the wider diameter 16x25 vs the 12.5x25 in the 2000. Also they have uprated C146 from 2200uF to 3300uF in the parts list (though mine is fitted with 2200uF from the factory). There are also some small (6.3 x 11) unlisted electrolytics on this board, C260 and C261 both 47uF 50V. It seems another user, jpb, ran into this as well!.

[Kjelt]

I wouldn't select any capacitor taller than the large 6800uF which barely leaves a gap and is 35mm high.
Farnell 1973521 fits the 12.5 dia 25mm high dimensions of the original but is only rated 2000 hours at 105C. I think I will take half the life vs much greater risk of mechanical damage

I agree, I will use those instead, the originals were also that spec so they lasted 20 years, no reason why the new ones shouldn't either.

[Kleinstein]

There analog part is somewhat noise sensitive, so one should avoid switched mode regulators. If really needed one might improve cooling.

I would be careful about using larger capacitance, as this will increase the current load to the transformer and give a slightly higher voltage and thus more loss at the regulators.

[Nuno_pt]

Back from Holliday yesterday.

Kjelt yes all my caps fit inside with the cover put in place, there is a small gap, but they fit, meter is close and open to see if there is some scratch on the caps, but nothing.

The TL866 haven't arrive yet, will've to see if it stops in customs, last time something stop there took 2.5 months to be deliver to my home.

I got the price of calibration from an Lab here near me, they quote 390€ + 23%VAT.

Next step will be to burn the new A19 firmware on the new EEPROMS, when the TL866 get here.

[TiN]

Why not A20, if you decide to go calibration by lab?

[Nuno_pt]

Hi TiN, yes that is my first bet, if I can find some lab that make a better price, I see on some of your K2001 topic that Tek in Germany charge about 500€ with VAT, so this here seems on the higher side, will've to ask in other labs and even on UK, Germany, etc. to see what is the best price, if I find a cheaper one will burn the A20 and sent it for full calibration.

It has also cross my mind to send it to the US for calibration since there is a lot cheaper, some post here has values of $75 for 6.5 digits DMM, but how would the Cal hold with the trip to this side of the pond?

[electricar]

Hey folks,

thank you for the Farnell BOM. It was so much easier for me to get the right BOM for those who cannot buy at Farnell and made instead a BOM for Mouser. I searched only for stocked parts, so the caps on Farnell and Mouser are mostly different parts (other partnumber).
I replaced the old caps yesterday and everything is working well.

Mouser partnumber:

804-39SF020A7INHE
661-EKYA630E101MJC5S
667-EEU-HD1H102
661-EKZN160E222MK20S
661-EKYB250E682MMN3S

Regards

[Kjelt]

Today I finally got my device programmer working so I just modded my first of two Keithleys.
First I placed an extra black heatsink on U119 already on the before picture.
Then I removed the elco's.
I wanted to place also a heatsink on U126 but this would not fit , it would touch U119 and the elco in front of it.
So i made a custom small heatsink from 4mm aluminium, a 3mm tap in it, put a small thermal compound sticker on it to make the heat transfer better and screwed it with a 3mmx6mm conical screw.
Works for me.
Then I removed the I2C calibration eeprom U136. Read it out and copied it to a brand new chip, resoldered the new chip.
Replaced the OTP eprom's with firmware A05 with the SST 39F020A flash eproms with firmware A19 (thanks to TiN and his brilliant website )
Recapped , i put the two elco's that are close to the voltage regulator a bit in an angle so there is more distance between them.
Then came the final moment, power on.
Beep..... A19  YES!   Three errors  Oh no... couldn't write them down quickly enough but from memory one was 812.
Shock.... power off.. wait three seconds... power on.... A19... no errors  uhhhhh 
I do not get any errors any more, so is this normal after changing from A05 to A19 firmware you get this or whats up?
Anyway checked quickly with a 10V source if the calibration is still ok, and it is 
Any advice, or close her up and start using it again?

[Nuno_pt]

Good work there Kjelt.

I'm still in backlog with mine, been working on some projects more old, that I need to finish first.

Since you remove and read the U136 that contains the calibration data, I'm guessing that reading one with a fresh calibration, and burn the data on a new one and put it on another DMM, that DMM would be calibrate?

If the above would work, we can burn A20, and if we find one DMM with A20 and in CAL, it's just read and burn the new U136.

New firmware and new CAL.

[Kjelt]

I might miss something but the Cal data is unique per dmm since each one has a different "error" in its reading. So yes you could switch to a working A20 version but then you need to know exactly the layout of the cal file and what parameters have changed and checksum etc.
Else you would probably end up with a wrong calibrated device.
So i have the data of my cal device and can post it tomorrow if you are interested but it makes not much sense without knowing what offset holds which data or you should make the chip in a zif socket and experiment with changing some data and see what happens.

[saturnin]

I wanted to place also a heatsink on U126 but this would not fit , it would touch U119 and the elco in front of it.
So i made a custom small heatsink from 4mm aluminium, a 3mm tap in it, put a small thermal compound sticker on it to make the heat transfer better and screwed it with a 3mmx6mm conical screw.

Sorry to be blunt, but that heatsink is totally useless. I will not have any significant effect. Your unit is more than 20 years old and LM340T15 regulator has survived it without any troubles. Even without a heatsink. Keithley designed it well...

[Macbeth]

There is no need to desolder U136 EEPROM to read or write to it. I know with other Keithleys (2001, 2002) you can hold the RESET line to stop the MCU working and can play about with the EEPROM at will, but with the 2000/2015 that doesn't work. (Something to do with Tri State?). Thankfully all you have to do is remove the firmware PROMs U156/U157 from their PLCC sockets and switch on and the U136 is your oyster.

Using a typical SOIC8 clip on U136 with your TL866 is problematical because of the big electrolytic in the way, so just wire a couple of micro grabbers for the data pins and croc clip to chassis for ground. No need for Vcc as that is provided when you switch the K2000 on.

Now - firmware change from A19 or A20 does destroy your calibration. Or rather it doesn't, because if you go back to A19 you will find it is OK.

Some investigation is needed to find the memory spaces that have changed so a simple reflash of the EEPROM could be "good enough" for an A20 firmware upgrade without a full recal. Not having to desolder and resolder the EEPROM will go a long way towards that goal! 

[Kjelt]

Sorry to be blunt, but that heatsink is totally useless. I will not have any significant effect. Your unit is more than 20 years old and LM340T15 regulator has survived it without any troubles. Even without a heatsink. Keithley designed it well...

Yes for Keithley the unit should last 5 to 10 years and than it is written off and if the design withstands it, that is fine. From that POV it is build well.
If you look at the defect list for this type you see that most issues are bad elco's and bad regulators (could be that the first is the cause of the second, that I do not know).
If you then look at the layout of these components you see that the regulators are almost put against the elco's and there is no active airflow in the device.
I measured the elco's that came out and they still are ok ESR and capacitance wise, so no need to replace them as well ?
I do not agree. I think that if the unit is open and you can make it better and last another 10-15 years with an half hour extra work than I will do that.
The reason and use of the heatsink is to spread the heat a bit more and drop the temperature of the regulator a couple of degrees, giving the elco a little more headroom.