Author Topic: Restoration glory of Keithley 2001 DMM  (Read 201744 times)

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Offline TiN

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Re: Restoration glory of Keithley 2001 DMM
« Reply #75 on: February 08, 2014, 07:34:33 pm »
Calibration constants from K2001 can be read using GPIB command.

Table C-2 of 2001-905-01G calibration manual lists the response to the :CAL:PROT:DATA? query. The response is an ASCII string of 99 numbers separated by commas, and is not affected by the FORMAT command.
Constants listed in Table C-2 are shown in the order they are sent.

Here values from cal'd unit #7 and from first 2001 (not calibrated)

Pretty sure all these stored in 24C16 I2C EEPROM located on digital board. Will read out it later on rest units.

EDIT:

And actually, seem like there is hidden 8.5 digit mode using remote control via GPIB on Model 2001 as well, like on HP's.

This query outputs 8.5 dig value as a readout
:FUNC 'VOLT:DC';:VOLT:DC:NPLC 1.000000E+1;:VOLT:DC:RANG 2.000000E+0;:VOLT:DC:DIG 9;:VOLT:DC:;REF:STAT OFF;:VOLT:DC:AVER:TCON REP;COUN 10;STAT ON;ADV:STAT OFF;
:FORM:ELEM READ;

DIG 9 means 8.5d, while DIG 8 is native 7.5 mode.



And yes, i tried DIG 10 too, it gave ERROR -222, value out of range, LOL  :-DD
« Last Edit: February 08, 2014, 08:26:33 pm by TiN »
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Offline TiN

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Re: Restoration glory of Keithley 2001 DMM
« Reply #76 on: February 09, 2014, 07:58:28 am »
As expected, calibration data stored in that I2C EEPROM as raw data.
I did not want to desolder IC, so borged a little I2C dongle to hook TL866 programmer (Thanks Dave, bought one for 60$ with bunch of adapters after EEVBlog video episode. Good tool).
There was a caveat - as I2C have open-collector lines, you don't want CPU to capture bus, in that case you will not be able to communicate with EEPROM by remote programmer.
Luckily - there is easy solution, tie RESET to ground, and there is a test post TP602, which easy to use to do so.
After keeping reset low, and power on - no problems to read/write EEPROM from TL866.

Whole setup, how i did it:



Binary image from digital board S/N A19956 ROM

Quick look with hex-editor:



Some values I was able to correlate to earlier read constant values from :CAL:PROT:DATA? query.
Need check what other formats are used for float-hex representation.

And there is some checksum algorithm to check ROM contents integrity, because if I try change calibration dates by hex editing - meter detects abuse and gives funny error :)

+

Amount of exclamation marks gives us feeling, that Keithley R&D were taking calibration serious enough  :-DMM
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Offline TiN

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Re: Restoration glory of Keithley 2001 DMM
« Reply #77 on: February 14, 2014, 04:28:45 pm »
Teaser:



What I'm doing here? Any guess?
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Offline sync

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Re: Restoration glory of Keithley 2001 DMM
« Reply #78 on: February 14, 2014, 04:35:24 pm »
Homemade weston cell? >:D
 

Offline TiN

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Re: Restoration glory of Keithley 2001 DMM
« Reply #79 on: February 14, 2014, 04:52:34 pm »
Does it look like a cell, lol ?

Guess more.
It's something to do with photos above, but not directly related.
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Offline sync

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Re: Restoration glory of Keithley 2001 DMM
« Reply #80 on: February 14, 2014, 05:01:14 pm »
Does it look like a cell, lol ?
The left fluorescent tube looks a bit like one.
 

Offline TiN

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Re: Restoration glory of Keithley 2001 DMM
« Reply #81 on: February 14, 2014, 05:02:54 pm »
No, i'm building LTZ1000 reference, no need any cells :)
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Offline sync

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Re: Restoration glory of Keithley 2001 DMM
« Reply #82 on: February 14, 2014, 05:07:32 pm »
And you destroyed all your CFLs so they can't disturb your measurements?
 

Offline TiN

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Re: Restoration glory of Keithley 2001 DMM
« Reply #83 on: February 16, 2014, 12:07:38 pm »


It was an mercury UV-C lamp for G23 socket, but I could not find any place to power it on normally , so just used CCFL inverter to create discharge in lamp :) Was desperate to erase UV EPROM 27C4096's for rest of my Keithley 2001's.



Just disconnected starter bulb and capacitor, and provided high voltage to opposite cathodes to ignite discharge.

Around 3 min exposure above ROM was enough to erase it. TL866 programmed it well afterwards.
Now all boards have A08 firmware, which is good for cal. Not sure about "B"-version firmware's tho, how they
relate.

P.S. Meanwhile DC-DC convertor for front panel VFD which takes +5V and converts to AC filament voltage and +60VDC segments in calibrated unit ceased to work. Meter was just capturing log of LM399 breadboard overnight, and in morning next day i saw no display. GPIB worked fine, so no other damages. No smoke, no fireworks, just stopped working. Replaced digital board, reflashed calibration I2C EEPROM on new board, checked front panel board - all now working fine and measurements match. In such moments you appreciate modular construction, when can replace digital side without touching analog board. Will check pesky DC-DC convertor later, but initial check showed no 60VDC output, and current consumption over 1A (normally working digital board takes ~0.85-0.7 A on +5V).

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Offline SeanB

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Re: Restoration glory of Keithley 2001 DMM
« Reply #84 on: February 16, 2014, 12:43:23 pm »
That Phillips UV lamp will have a very short life with the way you are driving it. But with erasing for under an hour at a time you will have a lot of use before the cathodes go totally open. You should connect the unused wire on each side to the lead to reduce hot spots on the cathodes, it does work on IS lamps.
 

Offline casinada

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Re: Restoration glory of Keithley 2001 DMM
« Reply #85 on: February 17, 2014, 02:02:27 am »
If you need to erase an eprom, just expose it to natural light (sun) :) No need to play with broken glass unless is night time and you're in a hurry.
:)
 

Offline TiN

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Re: Restoration glory of Keithley 2001 DMM
« Reply #86 on: February 17, 2014, 04:19:26 am »
SeanB

Yes, I know, these lamps need hot plasma to recover their cathodes during operation, but current dirty way for couple minutes to erase UV ROM twice in year or so it will do fine.

casinada

Tried that, ROM was on balcony for 3 days, not worked, data still intact :) Maybe it was low UV days.

ALL

I managed to get Keithley 2002 into my hands, should I post about it here in thread too (as it's kinda similar to 2001) or create separate thread, as it's another league device (it is actually)?

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Offline chickenHeadKnob

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Re: Restoration glory of Keithley 2001 DMM
« Reply #87 on: February 17, 2014, 05:47:40 am »

ALL

I managed to get Keithley 2002 into my hands, should I post about it here in thread too (as it's kinda similar to 2001) or create separate thread, as it's another league device (it is actually)?

Please create a new thread, if only for search purpose/posterity. I love your photography and the teardown  and repair threads will be searched and refered to by others years in the future, particularly by non-forum members who get a google hit. Much personal self-interest in the 2002. Thanks.
 

Offline TiN

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Re: Restoration glory of Keithley 2001 DMM
« Reply #88 on: February 22, 2014, 04:54:15 pm »
:-) Need find 24C16 in DIP package first to try more..
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Offline KJDS

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Re: Restoration glory of Keithley 2001 DMM
« Reply #89 on: February 22, 2014, 05:58:57 pm »
:-) Need find 24C16 in DIP package first to try more..

if there's one in a 2015THD then I can probably spare one.

Offline TiN

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Re: Restoration glory of Keithley 2001 DMM
« Reply #90 on: February 22, 2014, 06:03:20 pm »
Don't worry, I2C EEPROMs are popular as a dirt, i'll find one somewhere.
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Offline macboy

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Re: Restoration glory of Keithley 2001 DMM
« Reply #91 on: April 01, 2014, 01:47:10 pm »
Based on TiN's recommendation, I am going to replace the electrolytics in my four 2001 meters. Do you have specific recommendations on what replacements to use (brand/series)? You mentioned also replacing diodes, which ones are you referring to, can you highlight them in a photo or give part numbers? I really appreciate all the hard work you've done with reverse-engineering the schematics.

You have at least one meter with a MEM1 or MEM2, correct? Can you read and post a copy of the NVSRAM contents here?
 

Offline TiN

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Re: Restoration glory of Keithley 2001 DMM
« Reply #92 on: April 01, 2014, 02:27:02 pm »
Congratulations, that's a correct questions you asked  :-+

Any meter can be modified MEM1/MEM2, make sure you have DS1245Y available on hand.

Can you help to please my eyes with your meters photos? :) Analog board, ADC boards and digital board?
I'll give you exact guideline what to do.

I used Chemicon KZE capacitors, but other first-tier vendor caps should be good too. Use same values, as original ones.
Be careful not to overheat pads, they are very easy to overheat and peel off, as no polygons there, just a thin trace.
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Offline TiN

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Re: Restoration glory of Keithley 2001 DMM
« Reply #93 on: July 14, 2014, 12:37:32 pm »
Little update.

One day I powered up one of my 2001's and was greeted by no display on VFD. Quicky suspected DC-AC inverter on digital board, and after quick check
that was a cause, there were no +55VDC to drive VFD segments.

Another 2001 have that inverter done as a custom module, while on other units it's just a ERG INC. E705 custom filled black block.



Module takes +5VDC input and outputs +55VDC and ~5.5VAC for filament.



Here's recovered schematics:



Anybody knows similar DC-AC blocks to replace dead one?
« Last Edit: July 14, 2014, 06:04:41 pm by TiN »
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Offline jpb

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Re: Restoration glory of Keithley 2001 DMM
« Reply #94 on: July 14, 2014, 02:50:51 pm »
According to the repair manual it is a replaceable part :
(http://exodus.poly.edu/~kurt/manuals/manuals/Keithley/KEI%202001%20Repair.pdf)

U625

MOD,DC-AC/DC, 5DV-5VAC/60DC,E705-E905VF,MO-30

Keithley part number :182-170B

I would try Keithley/Tektronix first. For my 2015 they were quite happy to supply a new VFD display and it was quite reasonable (£53 + VAT).

Edit : Though I note the manual has the output as 60VDC rather than 55VDC.
« Last Edit: July 14, 2014, 02:53:56 pm by jpb »
 

Offline cyr

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Re: Restoration glory of Keithley 2001 DMM
« Reply #95 on: July 14, 2014, 03:08:05 pm »
One of mine has B15 firmware, which is almost the newest (there is a B16). Are you interested in the B15 firmware? I need an excuse to finally buy a MiniPro programmer.

Did you ever dump your B15 firmware? I would be very interested in a copy...
 

Offline electronic_eel

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Re: Restoration glory of Keithley 2001 DMM
« Reply #96 on: July 26, 2014, 01:22:58 pm »
Just got a (used) 2001. Working fine so far. Only issues are the fan sounding like being at the end of it's lifespan, some dirt around the fan and some dim pixels on the VFD.

In addition to replacing the fan I plan to replace the thick electrolytic caps as suggested here and order a DS1245Y for mem2.

Any interest in photos of the boards? Analog board is rev. P, ADC rev. J, digital rev. K. Firmware ist B10. From the datecodes the build date seems to be 1999 or shortly after.

What are my options about replacing the VFD? Can you get just the VFD as spare part from Keithley or is it always the whole front panel? I guess that getting the original from Keithley isn't cheap, so any other ideas?
 

Offline TiN

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Re: Restoration glory of Keithley 2001 DMM
« Reply #97 on: July 26, 2014, 01:35:49 pm »
Congrats. Sure, please make photos of your hardware, ill add into 2001 revisions collection.
I dont have analog boards with rev.P

Also if you have tools its worth to get dump of firmware B10 and calibration data (stored in 24c16 i2c eeprom near cpu)

As of VFD, its tricky process. I was replacing VFD on Keithley 2400 before, it took an effort to carefully desolder it (i used solder wick to free every single pin from pcb). Be careful not to overheat pins as they are not very robust on glass.
Try to get VFD from Keithley or a front panel, I'd like to hear how much that would cost. Alternative option is to buy keithley 7001 from ebay with verified good VFD and replace VFD from there. Glass itself is same in 2001/2002/24xx/26xx Keithley's but front panel pcb is different.
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Offline TiN

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Re: Restoration glory of Keithley 2001 DMM
« Reply #98 on: July 26, 2014, 01:38:42 pm »
P.s. as of MEM2 upgrade, just replacing NVRAM chip is not 100% enough, i had plans to post article about proper procedure, but got other stuff to do and never finished it yet.

Could be a good reason to do so to help you :)
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Offline electronic_eel

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Re: Restoration glory of Keithley 2001 DMM
« Reply #99 on: July 26, 2014, 02:01:28 pm »
Hi,

thanks for your quick answer. So I'll contact Keithley and see what they offer me about the VFD and front panel. I'm not afraid of a bit of soldering, so I'll compare the prices to 7001 scanners.

Will make proper photos of the board when I change the caps. Unfortunately I don't have a EPROM reader at hand to get a firmware dump.

About the MEM: currently there is sitting a LH5164A-10L SRAM in the socket, the jumper is in the STD position. Is that normal? I've seen several photos where the socket is completely unpopulated without the MEM option.

And a probably stupid question: whats the best way to unmount the analog board? I guess you remove the front panel and slide it out to the front. But what about the rear input sockets? Do you have to unsolder them or is there a trick to get them out intact?
 


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