EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: TiN on September 22, 2014, 04:30:42 am
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Hello volt-nuts.
It's probably sickness, but one day I was thinking that having multiple KEI 2001's and 2002 ain't enough, and wanted to have some addition
to not so convinient Agilent 34970A at work, so I randomly bidded on abused Keithley 2000 from Israel (http://www.ebay.com/itm/KEITHLEY-2000-DIGITS-MULTIMETER-DIGITAL-MULTIMETER-/151405131225?ssPageName=STRK%3AMEWNX%3AIT&_trksid=p2047675.l2557&nma=true&si=M4C8RM%252BvLC9%252B9ZESnkAcpps8zKA%253D&orig_cvip=true&rt=nc), with a hope that somebody else would buy it.
As usually, Merphy gotcha me, so I won it with my single bid for $80USD. Meter arrived packaged nicely in big box, powers on and exactly as described.
VFD is intact, desprite missing front face plastic. I will use my donor 2001 front panel later, so not a problem here.
Functions are pretty much broken, shows overflow on ACV,ACI,4W, ramps readings like crazy on DCV,DCI,ohms.
Cranked it open, aha.... (http://dev.xdevs.com/issues/1159)
Pesky capacitors leaked their electrolyte causing major disaster on poor PCB.
According to date codes, this meter is already 20 year old :)
It fails pretty much almost every self-test (http://dev.xdevs.com/issues/1158).
So no wonder, one of power supply rails probably gone bad.
Will see how this worklog will go.
Did I got another endless repair project, or this baby will be up and running in no time?
Bonus included, for Keithley 2000 our chinese friends from bbs.38hot.net forums reverse-engineered schematics for analog part.
I got it mirrored on my site here (http://dev.xdevs.com/issues/874)
And as usual, all my data and photos are always available on related project page here (http://dev.xdevs.com/projects/kei2000/issues).
In worst case I got very well aged LM399 voltage reference, ha-ha >:D
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Current state
Gang switch desoldered, can measure voltages,resistances if connected to R115 input resistor and AGND.
Relay, power seem to be ok.
6800uF 16V need to be replaced
17V zener VR109 require replacement (SOT23-3 device), currently use pair of 11+6.2V zeners
AD706 need replace?
Errors in 40x series tests.
Chassis need some metalwork to fix bending :)
(http://doc.xdevs.com/doc/Keithley/2000/photo/clean1_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/clean1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/clean2_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/clean2.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/clean3_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/clean3.jpg)
Almost in calibration, even after all that butchery :)
(http://doc.xdevs.com/doc/Keithley/2000/photo/10vin_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/10vin.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/10kin_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/10kin.jpg)
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Article & docs
xDevs.com Repair log for Keithley Model 2000 (http://xdevs.com/fix/kei2000/)
??? ???????????????, ?????? ?? ?????? radiokot.ru (http://radiokot.ru/forum/viewtopic.php?f=10&t=116230) - for russian folks :)
Documentation section about Keithley 2000 (http://doc.xdevs.com/article/keithley-instruments/#2000)
jhzyou 126.com from bbs.38hot.net schematics (http://doc.xdevs.com/doc/Keithley/2000/K2000.pdf)
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so I randomly bidded on abused Keithley 2000 from Israel (http://www.ebay.com/itm/KEITHLEY-2000-DIGITS-MULTIMETER-DIGITAL-MULTIMETER-/151405131225?ssPageName=STRK%3AMEWNX%3AIT&_trksid=p2047675.l2557&nma=true&si=M4C8RM%252BvLC9%252B9ZESnkAcpps8zKA%253D&orig_cvip=true&rt=nc), with a hope that somebody else would buy it.
I'm looking forward to reading and following your repair efforts.
With that particular seller, many here will look and shake their heads in disbelief at how such equipment can be abused, but not bid due to normally ridiculously high asking prices.
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(http://dev.xdevs.com/projects/kei2000/repository/entry/photos/leak_brd_small.jpg) (http://dev.xdevs.com/projects/kei2000/repository/entry/photos/leak_brd.jpg)
(http://dev.xdevs.com/projects/kei2000/repository/entry/photos/leak_macro_small.jpg) (http://dev.xdevs.com/projects/kei2000/repository/entry/photos/leak_macro.jpg)
You still not replaced caps in your 20-year old gear? That's what happens...
Meanwhile dumped firmware ROMs here (http://dev.xdevs.com/issues/1160)
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Hello,
if you can repair the instrument you can find the latest firmware (A20) for the 2000 model here before they
repent of having made it public for free....
http://forum.keithley.com/phpBB3/download/file.php?id=1922&sid=b1e6c26ea52bbf76cd35f47f31259b3b (http://forum.keithley.com/phpBB3/download/file.php?id=1922&sid=b1e6c26ea52bbf76cd35f47f31259b3b)
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Thanks for firmware, but mine 2000 have non-erasable OTP EPROM chips, so I can't reflash it.
Not sure if I have UV 256KB EEPROMs in PLCC32 anywhere :)
Added few more photos for everybody enjoyment.
Teared apart meter..
(http://dev.xdevs.com/projects/kei2000/repository/entry/photos/k2000_assy_small.jpg) (http://dev.xdevs.com/projects/kei2000/repository/entry/photos/k2000_assy.jpg)
Top side of mainboard
(http://dev.xdevs.com/projects/kei2000/repository/entry/photos/k2000_top_small.jpg) (http://dev.xdevs.com/projects/kei2000/repository/entry/photos/k2000_top.jpg)
Bottom side of mainboard
(http://dev.xdevs.com/projects/kei2000/repository/entry/photos/k2000_back_small.jpg) (http://dev.xdevs.com/projects/kei2000/repository/entry/photos/k2000_back.jpg)
Back of front panel board
(http://dev.xdevs.com/projects/kei2000/repository/entry/photos/fp_back_small.jpg) (http://dev.xdevs.com/projects/kei2000/repository/entry/photos/fp_back.jpg)
Self-test status as received:
Last calibration date: 03/13/1995
Calibration counts: 1
Failed: 100.2, 201.1, 201.2, 300.1, 301.1, 301.2, 302.1, 302.2, 303.1, 303.2, 304.1, 400.2, 401.2, 402.2, 403.2, 500.1, 500.2, 600.1, 600.2, 601.2
Replaced caps, 7815, 7915, some JFETs, U109 (14094B register), U111 (DG211DY) from my donor 2001 yesterday night, few errors go away
Few self-test errors gone, now failed: 100.2, 301.1, 302.1, 302.2, 303.1, 304.1, 400.2, 401.2, 402.2, 403.2, 500.1, 500.2, 600.1, 600.2, 601.2
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After looking at all the other items from that seller all I can say is .... WTF? I like the obviously run over fluke 189 for $90 shipped to the US though.
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Necrothread revive!
(http://doc.xdevs.com/doc/Keithley/2000/photo/vfdhack1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfdhack5.jpg)
(http://doc.xdevs.com/doc/Keithley/2000/photo/vfdhack3.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfdhack6.jpg)
No, this is not 7001.
It's broken 2000 hooked up to front panel from 7001.
Obviously, technically it's possible to use 7001 or 2001 front panel in 2000, since it's same interconnect.
Both instruments series (2000,2700,2750,2790, name it, all single-line Keithley stuff) and dual-line using UART to send data from main DMM 68000 to front panel MC68HC705C8.
Issue is only different protocol commands, so someone persistive enough with plenty free time could bodge a little MCU in between to translate 2000's data/readings into 2001/7001's format and enjoy bigger, nicer VFD on 2000 instrument. I'm not gonna go that road. My 2000 native VFD panel is very dim, so I was wondering if 7001's display would work as is.
As result is no, I will go forward and desolder NEWHAVEN DISPLAY DD-51C glass from 7001 board and solder on 2001-112 front panel PCB, since I lack of one 2001 FP.
Why there is photo of 33120A there? Ahh, glad you asked, it's a trap for young players. Tell me why is that puppy shown? >:D
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VFD brightness fix
Today seem to be a good day for some fiddling with my broken 2000. One of issues, disregarding broken analog circuits is really really dim display. On usual daylight it was completely invisible, even without dark plastic plexi.
I tried to take photo of original state:
(http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/before_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/before.jpg)
Filament had 8.75 ohm resistance and had 2.11VAC across it during operation.
(http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/res_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/res.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/vac_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/vac.jpg)
VFD brightness drop from two reasons:
* Phosporus become aged if segments are on for long periods. This is visible by dim patterns on screen.
* Filament loose emission due oxidation
Not much can do for fixing segments itself, but we can try deoxidize filament and increase current across it to have more emission.
To do so, I used trustly Keithley 2400 SMU in source current mode. Started with 140mA and raised up to 180mA (6.5VDC compliance voltage)
for couple minutes to heat up filament.
(http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/deox_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/deox.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/filament_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/filament.jpg)
Now it become little better, but still not enough for me..
(http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/fix1_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/fix1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/fix2_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/fix2.jpg)
There are current limiting resistors near each filament pin on PCB, stock resistors R405,R412 12.1 Ω and similar on other side.
We can increase operation current by adding parallel resistors on top of original ones. I used three 22.1 Ω in 1206 size on top of each location.
(http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/fix3_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/fix3.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/rcurre_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/rcurre.jpg)
Result is satisfactory!
(http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/panel1_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/panel1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/panel2_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/panel2.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/panel3_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/vfd/panel3.jpg)
Now even with panel display can be read easily.
Of course this is temporary improvement, and after few years brightness will drop again, but it's not much else to loose. After all VFDs are giving you that warm fuzzy feeling, and have awesome viewing angles and contrast.
I think now this 2000 have chance to get my attention to actually fix it :-DD
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I would like to try to deoxidize the filaments of the 6517A display. The whole display is verry dim. Just one question, how do you specify the maximum voltage/current for the fillaments?
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I just carefully adjusted current from 10mA till it glow nicely orange like in photo. Adjust it slowly, and don't stress or shock display, as hot wires are easy to break.
6517 is dualline DD-51 VFD, so it's about double current than for segment one like in 2000.
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It worked, a little bit. The display is only a bit better, but it was very bad to begin with. I could tell by looking to the bare VFD which pixels where "bad" (the color was significantly different).
Just had to disconnect the display module and remove T901, this transformer drives the filament. Filament is driven on the outermost 2 pins of the VFD module. I had upped the voltage to 8,5V in 3 minutes, on which the the current reached 300mA. The filaments glowed a little bit, I didn't want to destroy them.
Good news, I did find the secret menu in the 6517A C03 FW: Press SEQ + Voltage source UP and the secret menu appears under menu => general. It also has en display burn-in setting, Ill give it a try.
BTW, just put my Keithley 199 FW on your FTP
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Cool, thanks.
If you have time , maybe you can make few photos of secret menu there for article (http://xdevs.com/guide/keithley_secret/)?
P.s. I think worth creating separate thread about 6517's, as we discuss it already in multiple different threads :D
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I just carefully adjusted current from 10mA till it glow nicely orange like in photo. Adjust it slowly, and don't stress or shock display, as hot wires are easy to break.
6517 is dualline DD-51 VFD, so it's about double current than for segment one like in 2000.
I strongly discourage using a constant current source to do this; use a (variable) constant voltage source.
The reason is that as the filaments heat up, their resistance goes up too. If you use constant current, the supply will dutifully push the preset current into the now higher resistance, giving more power and more heat, so higher resistance in the filament, which results in more power and more heat, so more resistance... you can get thermal runaway, and the casualty will be the filaments. If you use constant voltage, then as the filament heats up and the resistance goes up, it tends to reduce the current and therefore the power, providing protection from thermal runaway.
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Cool, thanks.
If you have time , maybe you can make few photos of secret menu there for article (http://xdevs.com/guide/keithley_secret/)?
P.s. I think worth creating separate thread about 6517's, as we discuss it already in multiple different threads :D
Good idea about the 6517 thread.
I haven't took any pictures, but I did upload a list of the secret menu settings. And some new versions of Keithley 2000 FW :-+
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macboy
Good point and trap for young players, thanks for highlight.
I was using SMU, so it was not so obvious, when I say it's constant current, as it have compliance voltage, and I had 200mA set for current source limit, and adjusting voltage compliance setting to get desired amount of current, so even if resistance drops, I would just hit voltage limit by compliance, or current limit by source.
If one use just CC PSU without any limiting on voltage - that may cause situation like macboy point out. Beware.
Thanks Smith! Updated catalog.
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Will the xdevs site add Keithley picoammeters too? They made quite some versions, they're pretty good.
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What you would like to know about picoammeters? In some thread I already posted some internal photos of 6485/6485 and SMU 2636.
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I'd like post everything (not just KI gear), as there is space for many other T&M.
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Cut from the private message:
"
Some time ago I was repairing Keithley 2000 and Keithley 2700 DMMs.
Both have defective LM339 (quad comparator) which controls FET switches.
Both units had small holes in LM339.
After replacement, both units worked just fine (checked on all ranges).
But how did the failure happened? All surrounding circuits are working fine...
I have only two ideas: defective series of IC's or overvoltage on -15V, +5 lines powering the comparator...
So I have two questions:
1. Did You have some units with broken LM339? Is it a common problem in 2000 series?
2. Two voltage regulators (LM7815M and LM7915M) are extremely hot. Is it normal ?
3. PCB near LM399 (Zener) is also quite hot. Is it normal ?
"
TiN answered:
"
1. I had few broken 339's in one of 2001. I have only one 2000, and it still waiting it's time to repair.
2. How hot? They run usually around 50-60ish C. It's okayish...
3. Yes, LM399 is ovenized zener, it's internal die thermostat runs about 90-95C to keep zener voltage stable and independent of ambient temp."
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The regulators do run quite hot indeed on both the 2000 and 2700's. There are a few revisions with different packages (SMD and trough hole) and different configurations. Mainly due to the nearby capacitors getting to hot and spill their guts on the PCB and componente on the early versions. I heared of quite a lot of units with defect regulators. I only had one (LM7915 on the 2700).
BTW I posted some K2000 internal pictures of several older units on TiN's FTP.
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Since we have gazillion of 2000 threads poping up every week, I'd think someone may be up for grabs on this one:
http://www.ebay.com/itm/Keithley-2000-multimeter-/161698789900?pt=LH_DefaultDomain_0&hash=item25a5ffba0c (http://www.ebay.com/itm/Keithley-2000-multimeter-/161698789900?pt=LH_DefaultDomain_0&hash=item25a5ffba0c)
All components seems there, just teared down. VFD likely be okay, getters are not white.
And price is okayish, if seller may accept reasonable offer :) I pass on this one, so who wants 2000 - that's ur chance :)
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Since we have gazillion of 2000 threads poping up every week, I'd think someone may be up for grabs on this one:
http://www.ebay.com/itm/Keithley-2000-multimeter-/161698789900?pt=LH_DefaultDomain_0&hash=item25a5ffba0c (http://www.ebay.com/itm/Keithley-2000-multimeter-/161698789900?pt=LH_DefaultDomain_0&hash=item25a5ffba0c)
All components seems there, just teared down. VFD likely be okay, getters are not white.
And price is okayish, if seller may accept reasonable offer :) I pass on this one, so who wants 2000 - that's ur chance :)
Seller accepted $95 shipped :)
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Dont forget to read firmware from it and post your findings here for us :)
I hope we can have most of data in one thread, instead of 50 threads about same meter :D
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Time to fix all this mess..
Parts removed for board repair :
(http://doc.xdevs.com/doc/Keithley/2000/photo/clean1_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/clean1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/clean2_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/clean2.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/clean3_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/clean3.jpg)
Anyone have 2000 for measurements around? I'm interested in resistances of R153 network, since schematics says it's two 3.6K resistor divider, but mine measures 3.60K pin 2 to center pin, while pin 1 to center pin is ~9K.
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Dont forget to read firmware from it and post your findings here for us :)
I hope we can have most of data in one thread, instead of 50 threads about same meter :D
With forum software like this, I don't think having one thread instead of 50 is necessarily any better. People who are participating in current/ongoing conversations have to contend with conversations on other subtopics that are taking place at the same time, and people who come later have to navigate the tangle of interwoven conversations to figure out the current thinking on a particular subtopic.
One thing that can help keep threads consolidated and long lived is if someone updates the first post occasionally to include a sort of FAQ and links to useful posts and outside resources (like your excellent XDevs project).
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TiN, I measured my R153 (in circuit): both resistances are 3.60K.
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Replaced vregs, R153 network, bodged zeners instead of 17V VR109 (don't have replacement yet),
Errors: 302.1, 302.2, 400.2, 401.2, 402.2, 403.2, 500.1, 500.2, 600.1, 600.2, 601.2
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Guess what... Part of problems come from gang switch. I removed it, and now can measure resistance and voltage if signal tied directly to input R115 and AGND (TP102).
302.1, 302.2 are also gone.
(http://doc.xdevs.com/doc/Keithley/2000/photo/10vin_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/10vin.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/10kin_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/10kin.jpg)
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Good find! I just replaced the switch on my 2002 last week and I know it can be disassembled. Unfortunately, all the contacts will come out but it may be possible to clean it and reinstall.
The switches are pretty cheap and are probably worth ordering if you can get them. If you can't, I can get a spare out to you if needed. I ordered extra switches for 'future' issues.
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Where do you order them?
I will take switch from my 2001 donor board, which i tear for parts. Switch can be disassembled by removing spring lock at front and pulling slider backwards all the way. Beware metal contacts, they will fly away as soon as free.
P.s. my RAID5 array at workstation gone sour, so I have it recovering on new 4TB drive, so had no chance to work on our noise comparison project yet. No data lost as first glance, but it takes time to get everything back. xDevs server is unaffected.
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I order my parts from Tektronix. I have building up a small collection of spare parts in addition to the repairs I have done.
Right now, the switches are on backorder. I have a couple spares on-hand but I ordered a couple extra due to at least one 2001 having a sticking switch. I had the switch fling apart on me, but this was after installing the new one. Can you tell what failed? Was it corrosion or some other problem. I think it is strange to use an open switch but I guess it works OK for the 8846A.
I am debugging the scripts now. Everytime I switch between the USB Prologix and the Ethernet version, something breaks. These all seem to be timing related and right now I am running the 2400 through its ranges. I can't imagine a pci based controller will have these weird issues.
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I guess I spoke to soon for switches.. Removed one from donor board, disassembled to clean internal contacts, and now after assembly it does not lock in with usual click.
And messing with original switch - i somehow installed few contacts in wrong direction and now slider stuck inside, breaking everything. |O Murphy gotcha me on these pesky switches.
So I'm in for couple, if you ordering. ;)
UPDATE:
Assembled switch somewhat locked in front position for now, run selftest.
Errors: 400.2, 402.2.
Ohms 2W and 4W reading incorrect in middle ranges. 10Meg and higher is ok.
1VDC = K2001 : 0.999991, K2000 : 0.999948
2VDC = K2001 : 1.999976, K2000 : 1.99994
5VDC = K2001 : 4.999966, K2000 : 4.99999
10V = K2001 : 9.999905, K2000 : 9.99988
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I think I have two at home, and one or two on backorder.
If you want one or both, let me know. I will still be good with the backordered switches. I thought I was going to replace all of them, considering my Agilent meters that had worn contacts. Never hurts to have a backup plan.
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I'd get two from backorder extra, no need urgent, it would still take a while till I get everything else fixed properly.
Here are the bastards:
(http://doc.xdevs.com/doc/Keithley/2000/photo/sw/orig_pads_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/sw/orig_pads.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/sw/orig_sw_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/sw/orig_sw.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/sw/clean_pads_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/sw/clean_pads.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/sw/new_sw_1.jpg) (http://doc.xdevs.com/doc/Keithley/2000/photo/sw/new_sw.jpg)
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Since we have gazillion of 2000 threads poping up every week, I'd think someone may be up for grabs on this one:
http://www.ebay.com/itm/Keithley-2000-multimeter-/161698789900?pt=LH_DefaultDomain_0&hash=item25a5ffba0c (http://www.ebay.com/itm/Keithley-2000-multimeter-/161698789900?pt=LH_DefaultDomain_0&hash=item25a5ffba0c)
All components seems there, just teared down. VFD likely be okay, getters are not white.
And price is okayish, if seller may accept reasonable offer :) I pass on this one, so who wants 2000 - that's ur chance :)
Seller accepted $95 shipped :)
Arrived today, well packed and all complete. Meter in kit form! I connected all the big bits together and plugged it in - Error +514 displayed for a moment and then it seems to work just fine (only tested on DC volts so far though). Display is bright, case is in great condition, bench handle and feet all present and correct. Seems to be have manufactured 2005 so not too ancient.
Looks good so far, not bad for $95 shipped!!
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Damn, cant really go wrong for that kind of money! I definetly payed more for my older unit (with a dim vfd).
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Cool, photos or never happen :P
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$95 shipped K2000 kit, almost no assembly required!
Appears to need a bit of calibration, just about functions as a 2.5 digit meter at the moment. Front/rear selector switch needs a bit of fiddly re-assembly (but all the bits are there), and the current measurement wire has been cut to get the front panel off (fuse, holder, spring all present though).
Nice and tidy, just need to find out how to make it read useful values now...
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Poor current lead.. It is removable very easity from front panel, all is needed just push a spring and get it out.
Somebody was really desperate to take it out :--
Noticed your board using caddock network, as well as Isabellenhutte current sense resistor.
Can you have more photos for PCBA, covering few parts. Also if you have different firmware - dump would be great to have for collection.
Thanks.
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Poor current lead.. It is removable very easity from front panel, all is needed just push a spring and get it out.
Somebody was really desperate to take it out :--
Noticed your board using caddock network, as well as Isabellenhutte current sense resistor.
Can you have more photos for PCBA, covering few parts. Also if you have different firmware - dump would be great to have for collection.
Thanks.
Hi,
K2000 from Ian is sold to me, I can make dump and photos when arrive. I also have one K2015 with few problems and I have plan to solve and fix all problems on both DMMs.
Cheers,
Damir
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Nice score on that box of meter parts. I thought it would be much worse off, seemed like a sketchy story that someone wouldn't be able to get it back together. Not that it wouldn't have been worth the price it for the parts...
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How do you people get deals like this ? $95 for a Keithley 2000 is insane, I've never seen anything below $500, even for the trashed ones. Do you set up eBay alerts or something and then respond in less than a second to the seller ?
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Maybe it depends on the country. I got my broken K2000 for 100€ at Ebay Germany. Working ones sold at 200-400€. There was even a working one for 130€ buy it now. Sadly I missed it.
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Its a combination of luck, search for the right parameters, and hope for cheap shipping.
Some will only ship with mayor and fast (expensive) shipping companies. This messes up a lot of mostly heavy equipment.
Bidding will mostly end up costly. Its more about the buy now or make a bid.
Sometimes they post the name/manufacturer wrong, or just dont know what they are selling. I have seen expensive gear been sold as "measurement stuff" even "I don't know what it is, just bid".
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In the US, I've been able to pick up 3 K2000 meters for $260, $335, and $365, including shipping.
The first I won in an auction, the second I picked up from an international seller because it came with a scanner card, which would probably have run $225 on its own. The third I got for the Buy-It-Now price within a couple of hours of it being listed. I was willing to pay more for it because it was running a recent firmware, which is required for support by Keithley's IVI drivers. The two I've received pass self-tets, seem in spec, as best as I can tell, and agree with each other within tolerances on the measurements I've checked. One has a nice bright screen, the other is dim. The remaining model was reported by the seller to fail two self-tests, which I know from research aren't critical, and could be cleared by blowing out the dust, or replacing an input FET. I'll see when it arrives.
In the same period, I lost two auctions for meters that ended up going for $250 and $305 + shipping, and another sold with an HP33120A that went for $453. I've probably been checking my saved searches once or twice a day. If I valued the time I spent looking for these deals on ebay at, oh, lets say $100/hour, then my prices per successful purchase would probably be $100-150 higher.
In the US at least, you should be able to get a decent meter for well under $500 if you are willing to spend some time looking and wait for a deal. $95 for a "kit" is insane though...
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Oh, its also worth looking the K2000s recently sold on ebay. You'll realize that you see lots of listings for units selling for $500/up because those don't sell very quickly, but there are a fair number of sales in the $200-350 range.
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You're right, past listings show pretty low prices. I'll have to check more often to strike one of those deals. I don't leave in the US but even with $60 shipping, $200 would be awesome.
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I just received a 2000 that was built in 1997. A06 ROMs. Last calibration Oct 2007. Number of calibrations = 8. It appears that this unit was well taken care of the first 9 years of its life. I Paid $250 plus shipping.
Everything seems to work perfectly so far for DC volts, DC amps, and ohms which is most of what I use a DMM for. I will check out frequency and temperature features later.
I do not seem to be able to include any attachments. Is there a post minimum to post a picture?
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There is a Keitheley 2001 for parts that's gone for $200 tonight, it looked like a good deal. Sadly the shipping to France was $100.
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There is a Keitheley 2001 for parts that's gone for $200 tonight, it looked like a good deal. Sadly the shipping to France was $100.
I was watching that one. Was going to bid in the 5 minutes between the end of an appointment and the end of the auction. Unfortunately, the appointment went 10 minutes long. Just as well. I have enough projects with two power designs bench power supplies I need to fix, another two coming that may need a fix, and three K2000s that I need to decide among before selling off one or two of them. I would have dropped out of the bidding at $175 probably.
Nice score, VintageNut. If you are planning on controlling it over RS-232 I'd suggest using a modified cable that leaves the RTS pin unconnected. For some reason the K2000 is wired to drive that pin, and versions of the firmware up to at least A15 seems to do so. Unfortunatley, the PC side correctly tries driving it in the opposite direction. The result seems to be that the inverter built into the level-shifter IC has trouble keeping up to the detriment of its ability to send data over the Rx pin. With the RTS pin connected, my ~1995 K2000 would stop sending data after less than 100 bytes. With the RTS disconnected, it was able to answer a *IDN? query every second for hours and hours without issue.
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I do not seem to be able to include any attachments. Is there a post minimum to post a picture?
You can upload anything you want here (https://doc.xdevs.com/contact/) for hosting about T&M gear ;) No limits.
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Hello eas. It looks to be a pristine model 2000. I finished checking it out. Frequency counting works. Temperature measurement works. So, I am happy to have it in the collection.
I never use RS232 when controlling an instrument for my own amusement. I bought a KUSB-488B used last year for $200. I also bout two generic GPIB cables.
At some point I will take off the cover and inspect for capacitor leakage. Not sure if it is possible to see leakage without removing a capacitor.
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Added firmware A13 files, thanks!
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I've ordered a new ADM202 and some EEPROM chips. I want to fix the RS-232 and upgrade to A20. Thankfully I have a willing colleague with a cal lab at my job.
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I've ordered a new ADM202 and some EEPROM chips. I want to fix the RS-232 and upgrade to A20. Thankfully I have a willing colleague with a cal lab at my job.
*jealous* I am looking for a place to calibrate some or all of my gear.
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Managed to get few thermal images of K2000 guts (way more on images link).
(http://xdevs.com/doc/Keithley/2000/thermal/k2000_ir1.png) (http://xdevs.com/doc/Keithley/2000/thermal/k2000_ir3.png) (http://xdevs.com/ru/fix/kei2000/#IR)
Few parts heating up abnormally, so it's not 100% fixed/functional unit just yet, even tho it can measure signals quite accurate.
Sometimes still go wacky measuring resistance.
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Got replacement switch, yey!
(https://xdevs.com/doc/Keithley/2000/photo/sw/newsw_1.jpg) (http://xdevs.com/en/article/received-replacement-switch-keithley-sw-468/)
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The screws that hold the case on these, two countersunk ones under the case, do anyone know the dimensions?
It looks like M3 screws, but I wonder if the threading isn't metric but imperial (or what it's called), I don't want to force m3 screws into it, if it's wrong....
And, the handle for this ting (I have the 2015, but I guess it's same as 2000?), how does it look like, and how is it attached to the body?, I first thought it was similar thing as the handles for Agilent meters, but it's an big open area on each side of the meter, not at all similar to the agilent meters.
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just curious, does anyone replace the tantalum caps as well when doing a fresh run of capacitor replacement? (there is 6x 7343 and 11x 3528 SMD, i am "renewing" a used K2015).
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Unless they are blown from voltage/current spike, they rarely fail. There is no liquid to get out from them. I keep them original, if visually they are looking good. :popcorn:
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tnx for the tip and the useful information in xdev.com :)
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Can someone do me a real solid and measure the length, diameter, and thread pitch of the rear bezel screws? I'm trying to avoid paying $22 for a set of screws from Tektronix. :palm:
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Can someone do me a real solid and measure the length, diameter, and thread pitch of the rear bezel screws? I'm trying to avoid paying $22 for a set of screws from Tektronix. :palm:
quick measure using a caliper (mm). but i think this maybe a "inch" based screw due to the threads.
length tip to tip =13.5mm
unthreaded portion = 6mm (diam 2.55mm)
threaded portion =5mm (diam 3.55mm)
the threads when compared to a HDD screw fit on each other nicely, so i have to say its a 6-32 thread
**edit : after an alcohol bath ... the old used K2015 is now all shiny :-DMM
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Can someone do me a real solid and measure the length, diameter, and thread pitch of the rear bezel screws? I'm trying to avoid paying $22 for a set of screws from Tektronix. [emoji14]alm:
quick measure using a caliper (mm). but i think this is a "inch" based screw due to the threads.
length tip to tip =13.5mm
unthreaded portion = 6mm (diam 2.55mm)
threaded portion =5mm (diam 3.55mm)
the threads when compared to a HDD screw fit on each other nicely, so i have to say its a 6-32 thread
Awesome, thanks a ton!
I think worst case, I can use a normal screw of the correct length and either grind off a portion of the threads or leave it as is.
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Well, time has come, I might do some work on this poor abandoned 2000. Got also 1L of hydrogen peroxide from cosmetics shop to try whitening panel. It's like a cream consistency, should be easier to apply on surfaces, as I don't want just to dip everything into liquid.
(http://xdevs.com/doc/Keithley/2000/peroxide/ke2000_h2o2_1.jpg) (http://xdevs.com/doc/Keithley/2000/peroxide/ke2000_h2o2.jpg) (http://xdevs.com/doc/Keithley/2000/peroxide/ke2000_h2o3_1.jpg) (http://xdevs.com/doc/Keithley/2000/peroxide/ke2000_h2o3.jpg)
Now need just to have sun come out. :)
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As you are in Taiwan simply go to the harbour and find a mercury vapour fishing light and fitting. 400W mercury lamp will give out quite enough UV to do the job.
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And also plenty of unhealthy ozone and health risks.
I would not suggest operating 400W UV lamp anyone without very clear understanding of possible hazards.
Also harbour is somewhat far, so I'd rather just hold to a sun.
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Hmm... so we're going to see TiN with a suicide blonde mop of hair and a nice all over tan? :-DD
My 2000 could do with that de-yellowing treatment too. Watching thread... :-+
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Not UV lamp just a regular coated MV lamp. Will give enough UV to do the bleaching, but not enough to cause you damage, as the glass and phosphor will absorb most of it. just provides a lot of bluish light, though a clear UV lamp or a UV fluorescent disco lamp would also work.
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Would the type of UV lamps in a PCB exposure box work? Because they didn't do a thing for me when trying to erase some EEPROMs.
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It looks like a fluorescent UV Light Tube should work.
Look here:
How to fix yellowed plastics on old computers!
Only question is, where to get this type and concentration of hydrogen peroxide creme in Germany?
Would be nice to try on my Keithley 2400
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@HighVoltage
Here in the US, Sally Beauty carries some items that might be available in their locations in Germany.
http://www.mystore411.com/store/listing/792/Germany/Sally-Beauty-Supply-store-locations (http://www.mystore411.com/store/listing/792/Germany/Sally-Beauty-Supply-store-locations)
I also have some that I have yet to try. Maybe TiN can give some convincing results?
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Well, time has come, I might do some work on this poor abandoned 2000. Got also 1L of hydrogen peroxide from cosmetics shop to try whitening panel. It's like a cream consistency, should be easier to apply on surfaces, as I don't want just to dip everything into liquid.
(http://xdevs.com/doc/Keithley/2000/peroxide/ke2000_h2o2_1.jpg) (http://xdevs.com/doc/Keithley/2000/peroxide/ke2000_h2o2.jpg) (http://xdevs.com/doc/Keithley/2000/peroxide/ke2000_h2o3_1.jpg) (http://xdevs.com/doc/Keithley/2000/peroxide/ke2000_h2o3.jpg)
Now need just to have sun come out. :)
Unfortunately, that process is only a temporary fix. Yellow will come back in a short period of time. You can also get blotches of uneven color if you're unlucky.
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I've heard it's only temporary - but the temporary is in the order of years. Indeed, much like the original equipment!
It doesn't seem to onerous to give the bezels this kind of treatment every few years - I mean, if you are the tidy sort you would probably remove bezels to get at all the crumbs, grease, (tar & nicotine if you are so inclined) and other environmental crap, take the opportunity to clean the switches and touchpads even on modern gear after a few years of use.
...and if you were planning on sporting a shocking blonde hairstyle and gorgeous bronzed body anyway, then the visit to the beauty parlour to obtain the chemical stuff is neither here nor there :-DD
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TiN,
Be careful not to rub the silkscreen writing or logos after soaking in the hydrogen peroxide. They won't get bleached, but they will be softened to the extent that any rubbing can remove them (don't ask me how I know :palm: ). After drying, they will harden up again.
To others: the type of hydrogen peroxide commonly used for this is usually bought from a beauty supply shop, where they sell salon supplies like hair dyes, waxing supplies, etc. I use "40 vol" concentration, quite strong.
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TiN,
Be careful not to rub the silkscreen writing or logos after soaking in the hydrogen peroxide. They won't get bleached, but they will be softened to the extent that any rubbing can remove them (don't ask me how I know :palm: ). After drying, they will harden up again.
Oh I dunno, it seems like a golden opportunity to rid the display bezel of it's '7001 Switch System' provenance. ;)
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:) I got 4142's cover out on the sun, will see how it goes. If it work out well, next will be this 2000 and few 2001 panels.
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TiN,
Here's another trick I have learned. If the ABS (grey) plastic has dents in it, you can remove them with a hot air gun. ABS likes to return to it's original shape if you heat it to a just-plastic state. I set my hot air to about 140o but I don't 100% trust the calibration so YMMV. Use a small nozzle pointed directly at the ding and make sure to shield things like the display lens and overlay, they don't react the same way! Don't overheat either, as then the plastic will lose its 'memory' and won't return to its original shape.
My 4 year old once chewed up a Lego man's contruction hat, it was all squished and the plastic had whitened from the stresses. I put the heat on it (just heating the entire thing), first the white-ish marks disappeared, then it just went back to 98% of it original shape. It fits on the Lego man's head again, and you wouldn't know what happened to it. Lego is also ABS. I don't know any other plastics that will do this, most will just get soft and limp when heated rather than return to original shape.
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Anyone have extra K2000 transformer for sale? It's P/N TR-299. Mine ceased working out of no obvious reason on another powers during debug (no any output on secondaries, no heating, nothing at all).. :(
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No need for transformer, unit got fixed, calibrated and send to other volt-nut member :)
Calibration video:
vid (https://www.youtube.com/watch?v=cVgizEwATuI)
Performance test:
(https://xdevs.com/doc/Keithley/2000/calsw/kei2000_result_1.png) (https://xdevs.com/fix/kei2000/)
Used calibration path:
DC Voltage - Agilent 3458A calibrated summer 2015 -> A9 HP3458A PCBA with LTZ1000A -> my fixed HP 3458A -> Time Electronics 9823 -> Keithley 2000. This experiment was covered here (https://xdevs.com/article/volt_xfer/).
Resistance - Keithley 2001 calibrated Feb 2014 (https://dev.xdevs.com/projects/kei2001/repository/changes/cal/2001-0544257%20as%20returned.pdf) -> Resistor Vishay PG foil 10K -> HP 3458A -> Time Electronics 9823 -> Keithley 2000.
Also few comparisons were made using 3 DMMs together : 3458A-2002-2000:
10VDC, 3458A + 2002L + 2000 after 10V cal (https://xdevs.com/time10_k2k/)
1mADC, 3458A + 2002L + 2000 (https://xdevs.com/time_1ma_2000/)
10mADC, 3 DMMs on same loop (https://xdevs.com/time_10ma_2000/)
100mADC, 3 DMMs on same loop (https://xdevs.com/time_100ma_2000/)
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Hello Illya,
I'm not d'accord with your calibration procedure.
At first, there is no estimate of your basic 10Vdc and 10kOhm uncertainty in your lab, for evaluation of the overall 3458A uncertainty.
Then, in your performance test list, you did not add the 3458A uncertainties for the different ranges and modes, neither relative to your basic 10V/10k uncertainty, nor absolute uncertainties.
Therefore, all the deviation numbers of your K2000 are flapping in the breeze.
Additionally, as the KEI2000 has been adjusted just before this verification, its 24h limits should be taken as test limits, not the 1yr. limits.
That would detect any further systematic calibration errors.
Then, 10mVdc and 10 Ohm are at least already outside specification after your calibration / adjustment.
Obviously, there seem to be systematic errors in your setup.
You might do a better offset voltage nulling, to get better agreement.
Maybe you should better use a precise 10:1 / 100:1 Hamon divider to calibrate 10mV and 100mV ranges.
If the KEI2000 does not support offset compensation, it is necessary to do a better estimation of possible errors for 10 Ohm.
Same goes for the 3458A, usage of OCOMP is mandatory.
100mAac probably is also outside specification, as the 3458A already has 800ppm uncertainty for 60Hz.
1000Vdc is also very questionable, as the 3458A itself is not very accurate here, at least +/- 15ppm systematic error, according to specification.
For 10VAC, I assume you used ACV SYNC?
I saw the "MORE INFO" annunciator briefly, but I'm not sure, how you really made this measurement... generally, you should document all 3458A modes in a detailed manner.
Anyhow, for ACV SYNC, you should better use 7 1/2 digit resolution to get more stable and more precise reading on the 3458A, or at best should use Swerleins algorithm.
Then you may have used silicone or similar cables for Ohm calibration, and twisted plus and minus together.. so you will get big errors for 10k, 100k, 1M, and 10M, due to leakage currents.
I don't know, if the shielded 4 pole cable, you used during verification, is insulated with PTFE, or better material. That would improve measurement precision.
It's also not visible, whether you used appropriate delays on both instruments for 10k and 100kOhm ranges, when using OCOMP feature on the 3458A.
In summary, your calibration process and uncertainty estimations need to be improved.
Frank
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I don't know, if the shielded 4 pole cable, you used during verification, is insulated with PTFE, or better material. That would improve measurement precision.
Frank
Where do you buy such high quality PTFE based test cables, if I may ask?
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First of all, thank you for feedback. I agree on your valid points, and I intend to address them accordingly.
I'd like to note fact that I had this K2000 sent to voltnut just for a shipping cost, basically free. Ofc it does not justify crude and bodged up calibration procedure revealed here, but will hopefully help to understand why it was done this way. Meter already spent half a year sitting in the pile, waiting for "it's time to come", and I thought getting it sorta calibrated and giving out to less equipped hobbyist would do more good than harm.
Now excuses away, few details on 10V/10k. As input standard for DCV i used as is A9 module (unmeasurable TC), which was measured by last year calibrated HPAK 3458A/F732B (annual spec). More details are covered in short article above, how I transferred DCV to my 3458A. I did not use 10V for CAL, but direct 7.1V CAL. I expect that worsen uncertainty by 40%.
Cross check with K2002 (cal'd in 2007) and second K2002 (cal'd in 2009, but fixed psu issues) got agreement in 2.1ppm window.
10Kohm situation is much worse, as only reference was K2001 calibrated by local Tek.
Now for setup, OCOMP was not used due lack of time and no low-noise cabling either. Even worse, AC unit was blowing air just overhead , so temperature variation was also far from desired +/-0.1C.
100mA on 3458A is rather bad, thanks to 50ppm specced 1 ohm shunt used, revealed by 22ppm/K TC, while K2002 is at least twice better. (ACAL joker not involved). High probability that 1 ohm DCI shunt on A1 will get replaced with some decent VPG foil prior to final cal.
I do plan to spend some qual time writing (bodging) python calibration app, to properly setup instruments and support all required features, as well as generating friendly HTML reports with all data covered.
On good side, I have a project coming soon to do a full calibration of both my K2002, foil resistance standards and LTZ-modules to known and verified absolute uncertainty. After reverse transfer back to my 3458(which will stay home, operating 24/7 as usual) this will give us answer how off I am today. I expect numbers about 10ppm DCV and 90ppm 10Kohm. Hence the rush to get K2000 shipped, as I still working to prepare everything I'd take for calibration.
Also Time 9823 is not calibrated, waiting for same thing to get adjustments after good uncertainty is known.
Hope this train of thoughts is inline of what actually need to be done. Oh, and last thing - I'll be testing code and more similar stuff with K2001. I'll use 24h spec this time, and will be happy to hear you out on that as well. I'll post in my 2001 thread once I have something.
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Great job as always TiN :-+
As for Teflon coated twisted pair, etc. Really? I would much sooner trust TiN's (uncertified) FREE calibration than any other typical ebay offering K2000/2015 pulled from a rack and sold as working, proof of calibration if any a worn out sticker 5 or 10 years old. Let's get things in perspective!
But... between the beauty treatment, dodgy transformer, and calibration I seem to have missed the actual fix? :-//
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Tbh actual fixing slipped even for me.
I'd say it was more system repair, than individual parts troubleshooting. That's the excuse I have, not to be able reporting "it was bad opamp U153 which caused problem A, and bad resistor R272 which cause problem B" :--
As received, box was throwing all the possible errors, reading jibberish. Cleaned mess and replaced few parts in area where electrolyte from capacitors spread.
That fixed few self-test items, but still were bad reading. Then I had it sitting few months, forgot what was done already.
Switch replacement - got conditions when it sometimes work, sometimes not. Then sitting few months, again, forgot what was done already.
Recently issue was found to be one of infamous 2512 resistor on input FE circuitry, which got cracked due to PCB stress and barely making contact.
Replaced all of them with 25K PTF56 25ppm/K ones, no randomness anymore. But new issue - meter started to hang from time to time and reset itself from no reason.
Replaced SRAM chips, replaced firmware ROMs to 39SF020 Flash with A20 FW. Hangs/reboots seem to be gone.
Again sitting few months..
Vref voltage sometimes drop to some low voltage, causing selftest errors from 200.x and so on. So I started to check circuitry around VREF. That's when "Transformer died". Actually it was OK, just mains fuse got blown quietly without any magic smoke, as I messed up on power polarity while replacing LT1124 opamp near reference :o. Don't know how that happen. New LT1124 installed, all back to normal (sorta).
Again sitting a month..
After assembly meter pass self-test once it's cold, but after warmup it fails undocumented 306.2/306.4 tests (which were added since A19 or around that fw?).
Since it seem not to affect actual measurements, and I ran out of time, I let it be and calibrated box as is.
Violated my own rule of documenting everything, and here's the result in it's glory. So people, don't skimp on documentation, it's often more important than actual fixing.
Now it's almost arrive to new user, which has no equipment to debug or test it, so I'd expect no further work to be done. :-/O
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No, this is not 7001.
It's broken 2000 hooked up to front panel from 7001.
Obviously, technically it's possible to use 7001 or 2001 front panel in 2000, since it's same interconnect.
Both instruments series (2000,2700,2750,2790, name it, all single-line Keithley stuff) and dual-line using UART to send data from main DMM 68000 to front panel MC68HC705C8.
Issue is only different protocol commands, so someone persistive enough with plenty free time could bodge a little MCU in between to translate 2000's data/readings into 2001/7001's format and enjoy bigger, nicer VFD on 2000 instrument. I'm not gonna go that road. My 2000 native VFD panel is very dim, so I was wondering if 7001's display would work as is.
As result is no, I will go forward and desolder NEWHAVEN DISPLAY DD-51C glass from 7001 board and solder on 2001-112 front panel PCB, since I lack of one 2001 FP.
Is there any documentation on the protocol used between DMM 68000 and front panel MC68HC705C8? If yes, dimmed VFD could be replaced with a newer display interpreting display commands. Of course, it would look totally different and certainly not as nice as the original VFD. But still better than a dim VFD, though.
Perhaps I have to reverse engineer the protocol. Interesting to know if the main 68k controls individual VFD segment or is the protocol in a higher level.
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Is there any documentation on the protocol used between DMM 68000 and front panel MC68HC705C8? If yes, dimmed VFD could be replaced with a newer display interpreting display commands. Of course, it would look totally different and certainly not as nice as the original VFD. But still better than a dim VFD, though.
Perhaps I have to reverse engineer the protocol. Interesting to know if the main 68k controls individual VFD segment or is the protocol in a higher level.
For sure the front panel has its own controller, it's not done by the mainboard 68k. When you power on you will be given the version of the mainboard firmware (e.g. A19) followed by the display firmware (e.g. A02) as 'REV:A19 A02'
Nice little reverse engineering project - it should be quite simple (he says!).
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Its fairly simple, binary UART with 9600 speed if I recall correctly. Thats for 2001/2 and similar dual line VFDs, but i expect single line follow same idea. I had posted sample data captures using usual UART-USB dongle somewhere in my site years ago :)
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Hello everybody,
I just got a broken Keithley 2700 for free and I'm trying to fix it. I'm not a professional so i hoped to be something simple.
According to the PCB it's made in year 2000.
Symptoms:
In DCV, 2WR and 4WR it shows overflow "OV.RFLW" in all ranges.
In ACV, DCI, ACI it seems to work (shows something near zero, good enough for now)
DCV in detail:
When I short the Inputs, it shows (only) in 10V-range a voltage of -4.6V. In any other Range it shows overflow.
When I let the inputs open, it shows overflow in all ranges plus following behavior:
- in 100V and 1000V ranges the inputs have about -4 to -5V (depending on the meter I'm using and its impedance)
- in the ranges 10V and below the voltage starts at 0V and goes up to about -12.6V. Even with a 10K resistor (on the inputs) the voltage is still about 1.8V, so it's not just a static charge)
What I've done so far:
- According to the troubleshooting in the service manual (found in other thread: https://www.element14.com/community/docs/DOC-52772/l/keithley-service-manual-for-model-2700-multimeter-data-acquisition-system (https://www.element14.com/community/docs/DOC-52772/l/keithley-service-manual-for-model-2700-multimeter-data-acquisition-system)):
- checked Power Supply voltages - all ok
- analog signal switching states for DCV (Q101 Q102 Q114 Q136 Q109 K101 Q113 Q105 Q104 Q108) - all ok
- checked for blown caps and measured some of them on board - all look ok
- checked 8 pole switch - ok
- Relays look and sound ok
- all components look ok
- checked U115 LM339 Quad comparator - outputs seem to have the correct state - ok
Known issues:
- it looks like there was some moisture at the back of the board but it does not look very bad and I think that any problem in that area may not affect the analog part of the meter (hmm...)
- the battery is dead, so it sometimes displays "No Comm Link" but here the same, I don't think it's the main problem.
I will attach a thermal image of an area that cought my attention.
There are two little transistors Q111 and Q144 (both PNP MMBT3906L) getting about 80°C
May be unusual, I don't know.
Would be happy to get some suggestions! Thanks!
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Replace all electrolytic capacitors, clean or replace front panel switch, check or replace large SMD resistors chain that pass input signal, due to big size they are easy to crack and have loose contact.
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I will attach a thermal image of an area that cought my attention.
There are two little transistors Q111 and Q144 (both PNP MMBT3906L) getting about 80°C
May be unusual, I don't know.
Would be happy to get some suggestions! Thanks!
K2000 schematic is similar to K2700/K2015, the component numbering is different
https://doc.xdevs.com/doc/Keithley/2000/K2000.pdf (https://doc.xdevs.com/doc/Keithley/2000/K2000.pdf)
i suspect the 2 Q are the powering section to a LTC1050, iirc it is responsible for the "zero" reference. in my old K2015 which i fiddled with, the Qs around that schematic section are also hot, and prone to damage (iirc, if you tap the SOT23, the readout could move around). so this was the section that i repaired, i replaced the hot SOT23 with TO-92 (iirc it became 40C or something?). *edit i found out the SOT23 i had was operating at about 70C.
if i understand K2700, the 2 opamps leading to the final zero buffer output from LTC1050 are powered from 2 different rails, the guard opamp (pre-LTC1050 AD822) is powered from 18v? 15v, and the LTC1050 (*update U113?)is powered from 5v dropped thru the group of SOT23 "up there" supplied by 20v, quite a distance away. iirc the K2000 is diff from the K2700 in the 20v rail, the K2000 20v is unregulated (so it could be 21v? 22v? straight from the xfmr)
but a hot SOT23 may not mean it is broken, mine was working till i fiddled it to death haha. you could try to open the switch to clean the insides. or in my case, i removed the switch completely as i no longer wish to deal with the intermittent problem anymore.
the K2000 schematic was reversed by some guy in bbshot, it is not 100% accurate, i tried to do some small updates to the "K2015" schematic, it could be found here around post #19, it could be K2700 have further newer changes https://www.eevblog.com/forum/repair/repaired-keithley-2000/msg814292/#msg814292 (https://www.eevblog.com/forum/repair/repaired-keithley-2000/msg814292/#msg814292)
i think i do have a 99% working K2700 lying around somewhere ...
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And as usual, all my data and photos are always available on related project page here (http://dev.xdevs.com/projects/kei2000/issues).
Hi TiN,
Unfortunately a lot of the data is no longer available at your site. Will it be possible to restore them, in order to keep this thread complete?
BR, Rob.