Author Topic: Electrometer output stage , keithley 6517  (Read 24977 times)

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Offline Smith

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Re: Electrometer output stage , keithley 6517
« Reply #25 on: April 20, 2015, 05:29:29 pm »
I did swap the even and odd chips, it just gave an no com link message, nothing else. I think I will request the firmware again, but with an checksum to make sure it copied ok.

I reflashed with the C03 firmware wich worked. So erasing and flashing works. By the way, I could't find any secret menu in the C03 version.
« Last Edit: April 20, 2015, 05:34:25 pm by Smith »
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Offline TiN

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Re: Electrometer output stage , keithley 6517
« Reply #26 on: April 21, 2015, 04:24:13 am »
C03 does have same secret menu according to strings in firmware, maybe different keys.

I tried C05 on 2001 and had no much luck, same as you.
Meter just waits with message "Keithley 6517A Electrometer, Checking ROM, please wait...".
I waited 5 minutes, it's long enough. Swapping EVEN and ODD gives No comms, as that's standard reply of MCU on front panel when it cannot talk to main CPU.

Noticed ending of file had 0xFF's instead of 0x00's like in C03 or 200x series DMM meters.
So here's EVEN and ODD modified with zero's to give it a try.
Same stuff, no go

Pulled C05 from site catalog first, till we clarify working binary, to avoid people bricking meters.
« Last Edit: April 21, 2015, 12:26:25 pm by TiN »
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Offline Smith

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Re: Electrometer output stage , keithley 6517
« Reply #27 on: April 22, 2015, 02:27:42 pm »
Turns out C03 was the last official release. Too bad the C05 didn't work, the firmware still has some issues. No further info was available at Keithley.
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Offline plesa

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Re: Electrometer output stage , keithley 6517
« Reply #28 on: December 26, 2015, 07:52:23 pm »
Did anyone successfully upgraded 6517A to C05 firmware?
I'm just thinking if the firmware problems cannot be related to memory selection
https://doc.xdevs.com/doc/Keithley/6517/fw/C03/M27C4001%20EPROM.jpg
On Keithley forum it looks like released and working firmware
http://forum.keithley.com/phpBB3/viewtopic.php?t=15543
« Last Edit: December 26, 2015, 08:14:20 pm by plesa »
 

Offline Smith

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Re: Electrometer output stage , keithley 6517
« Reply #29 on: December 26, 2015, 09:49:48 pm »
Nope, I had contact with Keithley, and C03 is their final FW. C05 didn't work and was never meant to be released as far as they know. The device still has some problems, but it doesn't look like they will ever be solved
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Offline plesa

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Re: Electrometer output stage , keithley 6517
« Reply #30 on: December 26, 2015, 10:12:21 pm »
Thanks for update.
 

Offline plesa

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Re: Electrometer output stage , keithley 6517
« Reply #31 on: December 31, 2015, 02:47:03 pm »
I was thinking about starting related to repair of 6517A, but I rather use this thread.
Unit does not power up, which is quite often failure of 6517 (based on in formations on forums).
So I started to reading service manual and found there is lot of various power rails.All were OK and within spec.
Another step was connecting GPIB to check if the problem is not only related to display ( there is no beep after power on, only relay click).
On GPIB no communication at all, so I tried RS232 with same results.
What I remember from repairing K2002 is tat without display unit does not power up due to display self test).
Fortunately the display board in 6517A is the K2002 display board :)
It was question of two minutes to disassemble K2002 and hook display to faulty 6517A and bingo - unit is working.

Checked Voltage source - OK
Current measurement - OK

Firmware is C04 which seems to be latest working. Just uploaded to TiN Keithley repository.It does not use the ST Micro 27C4001 UV EPROM but OTP from Atmel 27C040.

Now I needs to check if I will found some cheap Keithley 7001 as a display donor.


 

Offline Smith

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Re: Electrometer output stage , keithley 6517
« Reply #32 on: December 31, 2015, 03:46:37 pm »
Won't the display be repairable? Is doesn't have that much components. Maybe it's a bad tantalum cap, or the flash/eeprom in U902?

I'm  hoping FW C04 will work, Keithley told me C03 was the latest release.
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Offline plesa

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Re: Electrometer output stage , keithley 6517
« Reply #33 on: December 31, 2015, 03:57:37 pm »
I was also thinking that it is something easy to repair, but it is for 98% vacuum in VFD.
Maybe there are some minor changes or firmware is for factory only. Many times the release is only due to the obsolescence.
 

Offline Smith

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Re: Electrometer output stage , keithley 6517
« Reply #34 on: December 31, 2015, 06:04:36 pm »
These devices have some mayor problems. I hope this will be resolved someday. Sometimes ranges show wrong values instead of overflows. This makes the auto ranging completely unreliable and impossible to use. I have seen this issue with multiple 6517A's. Even the 6517B I have seen has these issues. I have asked Keithley about it, but I never had any reaction.
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Offline plesa

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Re: Electrometer output stage , keithley 6517
« Reply #35 on: January 01, 2016, 05:09:09 pm »
Similar issue with not correct values I encountered on Keithley picoammeters 648x series. You needs to press some button to resolve it.
In meantime I purchased 7001 mainframe as display donor, but I noticed from TiN photos that it is not compatible ( 7001/2001 VFD has one contact row and 2002/6517 has two rows).
Display is soldered and with board only the meter is working. What I found recently that on positive voltage is dead one 2SK1412 transistor.
So when I exceeded output voltage above 680V the red LED on front panel is blinking and on output is only 680V.
Based on failure from beginning of this thread it looks like the weak point are the 2SK1412 transistors.
Maybe time to replace them with some recent one the most suiteble what I found is NDFPD1N150CG
http://www.farnell.com/datasheets/1792666.pdf
 

Offline Smith

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Re: Electrometer output stage , keithley 6517
« Reply #36 on: January 01, 2016, 08:09:47 pm »
I have used multiple Keithley 485 and 6485 picoammeters, but I have never had this issue before.
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Offline TiN

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Re: Electrometer output stage , keithley 6517
« Reply #37 on: January 01, 2016, 11:20:27 pm »
Display is still compatible, it's just leads forming. I just stretched pins far enough to reach second row, and it worked a treat (see my Kei2400 repair, where glass was broken).
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Offline plesa

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Re: Electrometer output stage , keithley 6517
« Reply #38 on: January 02, 2016, 12:08:12 am »
Display is still compatible, it's just leads forming. I just stretched pins far enough to reach second row, and it worked a treat (see my Kei2400 repair, where glass was broken).

Excellent, I just scored on almost new 7001 for $35 :) Thanks!!
 

Offline plesa

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Re: Electrometer output stage , keithley 6517
« Reply #39 on: January 09, 2016, 03:50:21 pm »
Repair continues. The 1000V range indicates overload (front red LED blinking) After replacing 2SK1412 MOSFET diode is blinking.
So I inspected rest of circuit and found and more faulty components
LM234 Current source
1N970B 24V Zener
V11713 Transistor, which seems to be 2N7000 ( according to service manual)
2SK1412 also replaced by NDFPD1N150CG
 

Offline plesa

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Keithley 6517A repair (FIXED)
« Reply #40 on: January 23, 2016, 05:51:05 pm »
Repair continues. The 1000V range indicates overload (front red LED blinking) After replacing 2SK1412 MOSFET diode is blinking.
So I inspected rest of circuit and found and more faulty components
LM234 Current source
1N970B 24V Zener
V11713 Transistor, which seems to be 2N7000 ( according to service manual)
2SK1412 also replaced by NDFPD1N150CG

Repair finished.
Found that two 24V zeners VR305/VR308 were damaged (not shorted) also one of 8,6V zeners VR307/309/310/311/312 was damaged (6,1V instead of 8,6V).
And Q316 2N3904 transistor was damaged.
Now is unit completely working, and I just needs to take thermal image to make sure it is not overheating.
Waiting for display donor (Keithley 7001).
 

Offline plesa

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Re: Electrometer output stage , keithley 6517
« Reply #41 on: January 28, 2016, 08:50:28 pm »
I just replaced display from 7001 unit. I noticed that display firmware in Motorola MC68HC705 is same for 7001 and for 2002 unit, but boards are not interchangeable. 7001 board does not work with 2002 unit.
Removing display was quite easy and fast. I used solder extractor and remove solder from all pins and peel of display with plastic knife.
I was thinking that's a pity to destroy almost new 7001 with 7057A scanner card. But for $35 it will be difficult or impossible to buy new display or display board ( someone mentioned that it is about 500 EUR).
Good news is that the 7001 scanner is working with display board disconnected completely or without VFD display. So unit is still usable with remote interface.
6517A is now with new VFD without any dim pixel :)
« Last Edit: January 28, 2016, 08:52:09 pm by plesa »
 

Offline Smith

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Re: Electrometer output stage , keithley 6517
« Reply #42 on: January 29, 2016, 05:24:00 pm »
The complete module with the vfd is 419 euro excluding vat at Tektronix.
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Offline plesa

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Re: Electrometer output stage , keithley 6517
« Reply #43 on: January 29, 2016, 08:19:09 pm »
The complete module with the vfd is 419 euro excluding vat at Tektronix.

Thanks.You have some catalog of spare parts with price list? Can you check if the VFD is available? I remember that for 2000 series meter someone mentioned that it is possible to order for 60 USD.
 

Offline Smith

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Re: Electrometer output stage , keithley 6517
« Reply #44 on: January 30, 2016, 10:19:36 am »
No I don't have a catalog, I just contacted keithley/Tektronix. It took some mails before I even got an answer (took a full year and multiple mails to get a quote on a Keithley 2000 vfd). FYI, the 2000/2015 uses the DD-52, goes for about 60 euro's, the 2700 use the DD-61 (if I remember corectly) which goes for about 70 euro's.

Most or all single line vfd's can be bought separately from the complete front PCB. As i remember they are between 60 and 70 euro's, so it's quite a difference. I have asked multiple people from Keithley why the dual line vfd isn't sold separately, one said it was sold separately years ago. He also told it was to difficult to solder (let me judge that BTW).

Keithley also offers a line of nice connectors, cables and accesoiries. You can also buy their triax cable per inch if you ask them.
« Last Edit: January 30, 2016, 10:49:00 am by Smith »
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Offline plesa

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Re: Electrometer output stage , keithley 6517
« Reply #45 on: January 30, 2016, 01:16:21 pm »
No I don't have a catalog, I just contacted keithley/Tektronix. It took some mails before I even got an answer (took a full year and multiple mails to get a quote on a Keithley 2000 vfd). FYI, the 2000/2015 uses the DD-52, goes for about 60 euro's, the 2700 use the DD-61 (if I remember corectly) which goes for about 70 euro's.

Most or all single line vfd's can be bought separately from the complete front PCB. As i remember they are between 60 and 70 euro's, so it's quite a difference. I have asked multiple people from Keithley why the dual line vfd isn't sold separately, one said it was sold separately years ago. He also told it was to difficult to solder (let me judge that BTW).

Keithley also offers a line of nice connectors, cables and accesoiries. You can also buy their triax cable per inch if you ask them.

Thanks. Maybe the availability is related to fact that original manufacturer of Keithely 2000/2010/2015 series VFD called DD-52 was Noritake Itron.
Recent units are using VFD from http://www.newhavendisplay.com/
You are right, Keithley 2700/7700 series is using DD-61.

Difficult part is removing VFD, that's a big difference between single line VFD where is much larger are of double side tape. On dual line is used only 7mm wide tape, which is easy.

I'm familiar with their accessory including their low noise cable with graphite coating ( this seems to be custom made, not comparable to Belden 9220 yellow triax used by Pomona ). Cable assemblies are pretty expensive, same for connectors.
Majority seems to be manufactured by
http://www.pasternack.com/bnc-triax-adapters-category.aspx
http://www.amphenolrf.com/connectors/triax.html
 

Offline TiN

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Re: Electrometer output stage , keithley 6517
« Reply #46 on: January 30, 2016, 01:23:43 pm »
Don't we all love plesa's posts, which always share bits of good details (at least for me, lol).

My CNMC triax cable is graphite based as well (inner core of middle shield to core wire).

And DD-52 is indeed Noritake VFD made custom for KI.
« Last Edit: January 30, 2016, 01:30:22 pm by TiN »
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Offline Smith

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Re: Electrometer output stage , keithley 6517
« Reply #47 on: January 30, 2016, 03:21:25 pm »
I really hate the yellow triax cable too. The keithley stuff is great.

I have heared  a lot of people about the double sided tape on the single row units. I thought it was quite easy to remove.
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Offline plesa

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Re: Electrometer output stage , keithley 6517
« Reply #48 on: January 30, 2016, 05:40:45 pm »
Don't we all love plesa's posts, which always share bits of good details (at least for me, lol).

My CNMC triax cable is graphite based as well (inner core of middle shield to core wire).

And DD-52 is indeed Noritake VFD made custom for KI.

LOOL, I really appreciate Prof. Keithley bow :)
Your CNMC looks interesting. Does it have SPC shielding? Keithley cables shield is difficult to solder.
Your CNMC is made by http://quirkwire.com/ by the way.
Few types are also made by Habia.

I really hate the yellow triax cable too. The keithley stuff is great.
I have heared  a lot of people about the double sided tape on the single row units. I thought it was quite easy to remove.
Belden 9220  is not for low current measurement, but Pomana used it anyway for triax adaptor, which is weird.
It is much more easier if you heat up the PCB e.g with hot air gun.
« Last Edit: January 30, 2016, 05:44:34 pm by plesa »
 

Offline plesa

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Restoration glory of Keithley 6517A Electrometer
« Reply #49 on: April 25, 2016, 08:15:42 pm »
Another 6517A electrometer repaired. It did not fall down from rack, but it has been damaged by overvoltage on input.
Which resulted in indicated overrange on all current and voltage ranges. On input was present 60V ( same on preamplifier output).
First of all I expected that input protection has been damaged
LS313 dual NPN transistor made by Micross was OK.
https://www.micross.com/pdf/LSM_LS313_TO-78.pdf
But it was ok including the input operational amplifier LMC6001
http://www.ti.com/lit/ds/symlink/lmc6001.pdf
All discrete transistors in shielded electrometer area inspected (2x 2N3904, 2x2N3906, 3x Supertex VN0550 and 3x Supertex VP0550) and Q402 (2N3904) and Q403 (2N3906) were damaged.

After replacing two NPN/PNP transistors unit is working again!!

Really helpful was schematic available in Keithley 617 ( pages 113-120 and  schematic 161)
http://www.univie.ac.at/photovoltaik/umwelt/ws2015/K617_original.pdf

Difference between 617 and 6512/6517 are in discrete FET input stage compare to low input bias current OpAmps used in recent versions.
Thats pity that Keithley do not provide schematic but Keithley gear seems to be more repair friendly ( only few custom made parts, but poor official assistance with repair and support).
I hope this will help to restore more Keithley electrometers :)

Be carefull and avoid contamination of PCB traces and resistors by fingerprints. PCB is quite sensitive to pads delamination. PCB needs some cleaning with IPA with toothblush and now it is going to be baked for 1h@50°C.
Firmware upgraded to B04.

 


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