Author Topic: Keithley 197A owners' corner  (Read 7761 times)

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Offline Vtile

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Re: Keithley 197A owners' corner
« Reply #50 on: May 10, 2018, 07:47:39 pm »
@ technogeeky: I'll give 10 for that project ^^  :)
 
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Offline tooki

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Re: Keithley 197A owners' corner
« Reply #51 on: May 19, 2018, 08:14:01 pm »
I wanted to chime in here in case anyone is watching. I had promised several times to release some code for doing 16x2 LCD replacement of the broken LCDs for these instruments.

As far as I know, the mapping from native LCD to a 16x2 LCD is complete and total. All displays for all modes translate to something on the 16x2 display. This includes status information, measurements, store/recall modes, dB mode, and troubleshooting modes. I even found a mode that I couldn't find in the manual: with GPIB card installed it sometimes says "OUT" using the alphanumerics.

I am in the process of extending the functionality shown below further, including:

* porting to Arduino Uno (trivial, just test which pins work)
* porting to ESP32 (wifi and/or bluetooth)
* release better documentation
* add back plotting support (native to Arduino)
* adding exporting for something to do plotting (like for sigrok)
* adding the ability for two of these devices to combine, displaying a combined stat on screen (power, for instance)

But since I just got back to a workable point, I figured I'd release the code so you guys can try to use it and/or comment or ask questions.

The Arduino project is located on GitHub. It is designed for a Arduino 2650.

Once I make a little more progress, I'll make an new thread about this with more documentation, pictures. I am essentially assuming you can do the 16x2 display wiring yourself (there are plenty of guides), and then you only need to pick off the GND, SCK, (MO)SI, and SS pins. If you want, you can skip the 16x2 display altogether and use serial as a display.

So I finally got around to getting this up and running. Great work!

I ported it to Uno (since it makes no damned sense to use up a Mega2560 for this!).

Here's the pin defs I'm using:

Code: [Select]
/* LCD: Pin Definitions
 */
/*      name    pin   //  color   used?   req?  uniq?   notes */
 #define RS_13   7    //          yes     yes   no      any ADC pin will work
 #define RW_12   8    //          yes     no    no      any ADC pin will work
 #define E__11   9    //          yes     yes   no      any ADC pin will work

/*      name    pin   //  color   used?   req?  uniq?   notes */
 #define D4      3    //          yes     yes   no      any ADC pin will work
 #define D5      4
 #define D6      5
 #define D7      6

and

Code: [Select]
/* SPI: Pin Definitions

    Note: the o_ is supposed to be a cute convention meaning "pin".
      so o_SCK is to be read "pin_SCK"
*/
/*      name    pin   //  color   used?   req?  uniq?   notes */
 #define o_GND   GND   //  blue    yes     yes   no      this isn't a real pin in the UI, but it must be connected -- P1006 pin 4
 #define o_SS    10    //  red     yes     yes   no      (Mega2650) this is the only pin that can be SS or CS -- P1006 pin 14
 #define o_SCK   13    //  yellow  yes     yes   no      (Mega2650) this is the only pin that can be SPI clock -- P1006 pin 12
 #define o_MOSI  11    //  orange  yes     yes   no      (Mega2650) this is the only pin that can listen from a masterm -- P1006 pin 13
 #define o_MISO  12    //          no      no    no      (Mega2650) this is the pin you'd use to speak to slave as master
 #define o_CD    49    //          no      no    no      one might be tempted to use command/data as a interrupt trigger, but we wouldn't get state info
(I changed the colors to my wires :P)


I turned off the "twiddler", since it serves no real purpose, and with the default timings, appears just as a pale flickery mess on my LCD.

I also found a bug: k197-spi.cpp declares #include "k197-state.h", but that header isn't included in the repository. But it doesn't seem to actually be used, since I just commented out the include and then it compiled fine.

Regarding documentation: Yeah, needs to be made more obvious! I would make a clear note of the SPI line names used in the Keithley documentation, as opposed to the official SPI names you used in the forum post. Ultimately, I'd love to know how the code works, so I can consider using something other than a character LCD, perhaps an LED display driven by a MAX7219 or something.

We should Skype again sometime and kibitz about it. :)
« Last Edit: May 19, 2018, 08:16:45 pm by tooki »
 

Offline technogeeky

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Re: Keithley 197A owners' corner
« Reply #52 on: May 20, 2018, 01:10:58 pm »
I wanted to chime in here in case anyone is watching. I had promised several times to release some code for doing 16x2 LCD replacement of the broken LCDs for these instruments.

As far as I know, the mapping from native LCD to a 16x2 LCD is complete and total. All displays for all modes translate to something on the 16x2 display. This includes status information, measurements, store/recall modes, dB mode, and troubleshooting modes. I even found a mode that I couldn't find in the manual: with GPIB card installed it sometimes says "OUT" using the alphanumerics.

I am in the process of extending the functionality shown below further, including:

* porting to Arduino Uno (trivial, just test which pins work)
* porting to ESP32 (wifi and/or bluetooth)
* release better documentation
* add back plotting support (native to Arduino)
* adding exporting for something to do plotting (like for sigrok)
* adding the ability for two of these devices to combine, displaying a combined stat on screen (power, for instance)

But since I just got back to a workable point, I figured I'd release the code so you guys can try to use it and/or comment or ask questions.

The Arduino project is located on GitHub. It is designed for a Arduino 2650.

Once I make a little more progress, I'll make an new thread about this with more documentation, pictures. I am essentially assuming you can do the 16x2 display wiring yourself (there are plenty of guides), and then you only need to pick off the GND, SCK, (MO)SI, and SS pins. If you want, you can skip the 16x2 display altogether and use serial as a display.

So I finally got around to getting this up and running. Great work!

I ported it to Uno (since it makes no damned sense to use up a Mega2560 for this!).

Here's the pin defs I'm using:

Code: [Select]
/* LCD: Pin Definitions
 */
/*      name    pin   //  color   used?   req?  uniq?   notes */
 #define RS_13   7    //          yes     yes   no      any ADC pin will work
 #define RW_12   8    //          yes     no    no      any ADC pin will work
 #define E__11   9    //          yes     yes   no      any ADC pin will work

/*      name    pin   //  color   used?   req?  uniq?   notes */
 #define D4      3    //          yes     yes   no      any ADC pin will work
 #define D5      4
 #define D6      5
 #define D7      6

and

Code: [Select]
/* SPI: Pin Definitions

    Note: the o_ is supposed to be a cute convention meaning "pin".
      so o_SCK is to be read "pin_SCK"
*/
/*      name    pin   //  color   used?   req?  uniq?   notes */
 #define o_GND   GND   //  blue    yes     yes   no      this isn't a real pin in the UI, but it must be connected -- P1006 pin 4
 #define o_SS    10    //  red     yes     yes   no      (Mega2650) this is the only pin that can be SS or CS -- P1006 pin 14
 #define o_SCK   13    //  yellow  yes     yes   no      (Mega2650) this is the only pin that can be SPI clock -- P1006 pin 12
 #define o_MOSI  11    //  orange  yes     yes   no      (Mega2650) this is the only pin that can listen from a masterm -- P1006 pin 13
 #define o_MISO  12    //          no      no    no      (Mega2650) this is the pin you'd use to speak to slave as master
 #define o_CD    49    //          no      no    no      one might be tempted to use command/data as a interrupt trigger, but we wouldn't get state info
(I changed the colors to my wires :P)


I turned off the "twiddler", since it serves no real purpose, and with the default timings, appears just as a pale flickery mess on my LCD.

I also found a bug: k197-spi.cpp declares #include "k197-state.h", but that header isn't included in the repository. But it doesn't seem to actually be used, since I just commented out the include and then it compiled fine.

Regarding documentation: Yeah, needs to be made more obvious! I would make a clear note of the SPI line names used in the Keithley documentation, as opposed to the official SPI names you used in the forum post. Ultimately, I'd love to know how the code works, so I can consider using something other than a character LCD, perhaps an LED display driven by a MAX7219 or something.

We should Skype again sometime and kibitz about it. :)

tooki:

I'm glad to hear you have it working!

I *almost* have the same thing working on an ESP32. I have a persistent problem with the SPI bus and reading the last status byte (which contains mode information).

And I agree documentation needs to be better. I have a little more documentation (namely I made pictures of the wiring connections at each step), but it was wrong until I re-did it so I didn't include it to avoid confusing more people.

I'll be happy to skype about it.

-tg
 
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Offline trobbins

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Re: Keithley 197A owners' corner
« Reply #53 on: June 06, 2018, 08:51:19 am »
I was lucky to pick up a faulty 197 with IEEE-488 interface with Analog Output and RF Probe options. 

One half winding of the power transformer primary was open-circuit.  240VAC is local, so I just use an external step-down transformer - works like a charm!
 
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Offline GregDunn

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Re: Keithley 197A owners' corner
« Reply #54 on: September 09, 2018, 01:07:05 am »
I found a 197A with IEEE-488 and analog out today at the Louisville hamfest.  $45 and in near-perfect shape (a few little scratches on the rear panel labels).  It tracks beautifully with my Fluke 8600 over the voltage range I'm interested in - and it's nice to see those extra digits, accurate or not.  Cheapest bench meter I've ever bought.  Oddly, it came without the handle and with little caps installed to cover the holes.  I don't think I've ever seen that before.

I do see why people are interested in replacing the EL Panel in the backlight, though.  Maybe I'll give that a shot.
 
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Offline GregDunn

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Re: Keithley 197A owners' corner
« Reply #55 on: September 11, 2018, 01:11:16 am »
Well... slightly premature in my previous post.  I checked the unit's AC, DC, Ω and A the first evening and all was well.  The next day, I rearranged my bench to put all the DMMs in one place and let everything warm up so I could check variance.  The Keithley started giving weird readings - the dB annunciator lit up sometimes, it showed V when reading Ω, gave a steadily increasing reading on ACV, etc.  Then I noticed the mode selector switches were sticking - this correlated with the weird readings most of the time.  My guess is that bringing the meter from its warm environment into my cool basement caused some of the lube on the switches to become more viscous.

I took the board out, tilted it so that any gunk would run out the front onto a paper towel, and hosed the switches down with 91% IPA.  Now it worked.  For a while... and then started sticking again. Repeated the procedure... exact same thing happened.  So I had to run out today and buy some high quality contact cleaner/lube.  This time I left nothing to chance; hosed the switches down, made sure nothing ran up the board into the components, let it dry, hosed it down again, repeat.  Exercised the switches in between applications.

So far (it's been on for a couple of hours) it's working at what looks to be appropriate accuracy - tracking the Fluke meters all the way up the scale on AC and DC.  I did a spot Ω check and it looked good (in fact much better than Saturday), but am going to repeat that later after I've thoroughly examined the AC/DCV ranges.

So, a question if anyone feels they can contribute: the stuff I used is a commercial product which specifically states it's a cleaner as well as a lubricant - I think it's Puretronics, which was about all they had.  Is there a need (or value) to hit the switch contacts with Deoxit after it cooks for a while?  Or should I quit now while it's working?   :-/O

Oh, in fact one more question: I took the IEEE-488 board out and left it disconnected while testing the unit.  I really don't need the capability; is there any downside to just leaving the board out and plugging the holes in the case?  I can't think of any.
« Last Edit: September 11, 2018, 01:13:06 am by GregDunn »
 

Offline rastro

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Re: Keithley 197A owners' corner
« Reply #56 on: September 11, 2018, 02:14:49 am »
... Oh, in fact one more question: I took the IEEE-488 board out and left it disconnected while testing the unit.  I really don't need the capability; is there any downside to just leaving the board out and plugging the holes in the case?  I can't think of any.

The GPIB is an option that was also sold as an upgrade kit.  Basically the modified cover and the board.  Removal should not impact the unit.  I don't think it would even make meaningful heat load difference inside the unit.

rastro

PS: the rubber buttons are a weak point for 9XX series; I've cleaned many.  ^-^
 

Offline GregDunn

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Re: Keithley 197A owners' corner
« Reply #57 on: September 11, 2018, 03:12:15 am »
I wasn't sure... it has 2 microcontrollers on the board, which is not an insignificant load; and it's stacked on top of the power supply regulator and another micro.  I may plug it back in and check the temperature rise with my IR before I button the whole thing back up.

While I had it apart I went in and cleaned the button traces on the display board.  The two I care about (dB and REL) seem to work OK.
 

Offline Cerebus

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Re: Keithley 197A owners' corner
« Reply #58 on: September 11, 2018, 02:29:14 pm »
While I had it apart I went in and cleaned the button traces on the display board.  The two I care about (dB and REL) seem to work OK.

About every other 197 I hear about has problems with that cluster of buttons until they are cleaned, mine certainly did. I suspect that should be considered a stock repair for 197s, of the kind you do as a matter of routine maintenance every time you happen to have one opened up for any reason.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline rastro

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Re: Keithley 197A owners' corner
« Reply #59 on: September 11, 2018, 03:37:11 pm »
I wasn't sure... it has 2 microcontrollers on the board, which is not an insignificant load; and it's stacked on top of the power supply regulator and another micro.  I may plug it back in and check the temperature rise with my IR before I button the whole thing back up...

The installation procedure for the GPIB option doesn't call for the instrument to be re-calibrated after field installation.  Apparently Keithley didn't feel this additional component would have a meaningful impact on system calibration.

See pdf page 53 of the manual:

http://physics.ucdavis.edu/Classes/Physics116/P116C_lab/Keithley_197AGPIB.pdf

It's not clear to me why you feel the need to remove this option.  I'd just leave it in - you may want to use it in the future.

rastro
 

Offline GregDunn

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Re: Keithley 197A owners' corner
« Reply #60 on: September 11, 2018, 05:09:42 pm »
I thought it might reduce the heating inside the case, and improve air flow.  If it's not an issue, I'll just leave it in.  Honestly, though, the chance of me ever using GPIB on an instrument are just about nil.  This is the only gear I have with that capability, for a start.   ;)
 

Offline tooki

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Re: Keithley 197A owners' corner
« Reply #61 on: September 11, 2018, 06:35:32 pm »
I would advise against removing it. You don’t want airflow!! Airflow causes temperature fluctuations and thus instability; you want everything to reach temperature and stay there. And it’s not as though these things get particularly warm anyway.

Additionally, airflow means dust or other contaminants, which you don’t want getting on the board. The high impedance circuits in this are sensitive enough to need guard traces; the last thing you want is convection airflow carrying in dust and grime and depositing it on the board.
 

Offline GregDunn

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Re: Keithley 197A owners' corner
« Reply #62 on: September 11, 2018, 06:55:36 pm »
I think you win.   :D  I did put the board on and measured some spot temps while it was cooking last night; they seemed very reasonable (max 113F at the regulator on the GPIB board) so I guess I'll leave it.

FYI and maybe of interest to the group: I cleaned the front panel switches four times with contact cleaner (yes, being ultra careful not to let any get on the board up in the sensitive analog section) and while they behaved a little better each time, there was clearly still some problem with the contacts.  I was going to give them a little Deoxit anyway, but decided to stop playing games and just squirt a minimal amount into the switches now.  It's been sitting for a few hours hooked up to a DCV source and so far it's rock solid.  Every time before, it started drifting and then jumping around by as much as tenths of a volt after a few minutes to an hour - and I had to switch modes a few times to get it to select the proper mode and settle down again.  After Deoxit, I've switched it from DCV to ACV and back, then to Ω and back, and it changed modes reliably each time.  Maybe I've gotten the last of the oxidation off the contacts.  We'll see after a little more running and some more "disturbing" the switch settings.
 

Offline GregDunn

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Re: Keithley 197A owners' corner
« Reply #63 on: September 13, 2018, 05:00:41 am »
Having already done a relative comparison of my three bench meters and found them to be very stable, I hooked them all up to a cheap AD584 voltage reference box which fortuitously came in the mail today (the KKMOON from Amazon).  I thought it might be entertaining, and it was!  My bench stayed at a very constant 24C for the 12 hours of testing, and to my surprise the Keithley read the exact values on the reference cal sheet, to the limits of its resolution, virtually from the moment it was turned on.  It wasn't a stuck reading, because I had to switch voltage outputs on the reference to get the 2.5. 5.0, 7.5 and 10.0 values.  So that was highly amusing.  The Fluke 8600 tracked perfectly, about 3mV higher, and the Dana 4200 drifted very slightly ending up about 3mV lower after a couple of hours and then not changing.

What does this mean?  I don' t know, but at the least I have 3 very stable voltmeters that are pretty good in the 0-10V range.   ;D
 

Offline GregDunn

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Re: Keithley 197A owners' corner
« Reply #64 on: September 21, 2018, 06:29:16 pm »
Going to bump this one last time for a while.  I got my second AD584-based voltage reference this week and hooked it up to the 197A.  Almost exactly spot on the listed values - just like the other reference I have.  I know that's not a confirmation that I'm in calibration, but it's a very positive result.

I'm going to order replacement electrolytic caps for this unit, to hopefully keep it alive and kicking for a few more years and forestall leakage issues.  The question: is there any reason not to replace all the caps listed below with Al-polymer units?  Except maybe the big one?  This subject seems to be discussed from time to time with no clear resolution.  For sure I'll be buying quality 105C rated parts no matter what, but I'm interested in owner's opinions.  New tantalums are likely better than the old ones, but are the polymers better still for filtering, in places where leakage is not a big deal?  I don't think any of these sit in the high impedance path.

15 µF 20V Ta [1]
10 µF 25V [4]
1500 µF 25V [1]
22 µF 16V [1]
2.2 µF 16V [1]
220 µF 25V [1]
470 µF 6.3V [1]
 

Offline rastro

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Re: Keithley 197A owners' corner
« Reply #65 on: September 21, 2018, 08:15:52 pm »
...
The question: is there any reason not to replace all the caps listed below with Al-polymer units?  Except maybe the big one?  This subject seems to be discussed from time to time with no clear resolution.  ...

I have had over a dozen K197's pass through my hands in the last 5 years.  I've never run across a leaky/bad capacitor.  As they say your "mileage may vary".  So my general approach is not to fix it if it isn't broken.  I'm sure there are many different views and experiences on this which will likely be posted...

There is no clear general answer.  Yes there are some pieces of equipment or specific boards that you do want to recap - usually they notorious and have a history of destructive failure.  For example if you just acquired a Tektronix 492 SA I would tell you to recap the SMPS - even if it's working it's probably marginal.  However from my Keithley experience I would not arbitrarily start replacing capacitors.

I don't want to discourage you from being proactive.  However you may want to consider the risk of creating problems with your rework.  For example you could create subtle problems like getting flux contamination on PCB near high impedance circuitry.  Wholesale rework could possible create cold solder joints or hairline break on a trace.  If you find a stability issue after replacing 10 items, where do you start looking?   :-//

The bottom line is you have weight the benefits.  I favor a less is better approach.  But good luck with whichever path you choose.

rastro
 

Offline technogeeky

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Re: Keithley 197A owners' corner
« Reply #66 on: September 22, 2018, 04:08:36 pm »

I have had over a dozen K197's pass through my hands in the last 5 years.  I've never run across a leaky/bad capacitor.  As they say your "mileage may vary".  So my general approach is not to fix it if it isn't broken.  I'm sure there are many different views and experiences on this which will likely be posted...


Agreed. None of my units have had bad capacitors.


There is no clear general answer.  Yes there are some pieces of equipment or specific boards that you do want to recap - usually they notorious and have a history of destructive failure.  For example if you just acquired a Tektronix 492 SA I would tell you to recap the SMPS - even if it's working it's probably marginal.  However from my Keithley experience I would not arbitrarily start replacing capacitors.

I don't want to discourage you from being proactive.  However you may want to consider the risk of creating problems with your rework.  For example you could create subtle problems like getting flux contamination on PCB near high impedance circuitry.  Wholesale rework could possible create cold solder joints or hairline break on a trace.  If you find a stability issue after replacing 10 items, where do you start looking?   :-//


I don't think that any of the electrolytic caps are anywhere near any sensitive circuitry, FYI.

It's also worth noting that the K197 is not very sensitive to pretty large voltage swings of the power rails. I know this because I supplied the voltage rails externally during a repair. I don't have advice on how this should influence capacitor replacement, but there you go.

The bottom line is you have weight the benefits.  I favor a less is better approach.  But good luck with whichever path you choose.

rastro


It's worth noting that while the warm-up time of the K197 is officially ~ 30 minutes (I think), it often settles faster. Also, internally it's a 6.5 digit multimeter ... averaged? sampled? concatenated? ... down to 5.5 digits. You can access this last digit if you have the analog output option (or if you figure out how to decipher the digital bus going to the analog board -- something I have not yet done.

 

Offline Cerebus

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Re: Keithley 197A owners' corner
« Reply #67 on: September 22, 2018, 06:03:45 pm »
Also, internally it's a 6.5 digit multimeter ... averaged? sampled? concatenated? ... down to 5.5 digits. You can access this last digit if you have the analog output option (or if you figure out how to decipher the digital bus going to the analog board -- something I have not yet done.

Erm, I think this is some half-remembered facts about another meter that you're mistakenly applying to the 197. Internally it's ±220,000 count, not 61/2 digits by any stretch of the imagination. The analogue output is ±4V in 1mV steps (derived from a 13 bit DAC) - there is no way that would provide access to any extended precision, even it if was there to be had.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline GregDunn

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Re: Keithley 197A owners' corner
« Reply #68 on: September 22, 2018, 06:32:07 pm »
The consensus, then, seems to be that the caps don't automatically need replacing on these.  I'm totally OK with this - I was just concerned because so many people have experienced leaky Al electrolytics or dying Ta caps on HP, Fluke, etc. meters which can cause damage to the boards.  But if that's not endemic to these meters, I'll settle for measuring the power supply voltages next time I have it open and doing a good visual scan for bulging or leaky caps.

On an unrelated note: where is the serial number supposed to be on these?  I have no external stickers and saw nothing that looks like a serial inside the case - just board model designations.  I'm thinking there should be a sticker and it's peeled off in ages past, but since this is the only one I've ever used...

 

Offline rastro

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Re: Keithley 197A owners' corner
« Reply #69 on: September 22, 2018, 07:47:50 pm »
On an unrelated note: where is the serial number supposed to be on these?  I have no external stickers and saw nothing that looks like a serial inside the case - just board model designations.  I'm thinking there should be a sticker and it's peeled off in ages past, but since this is the only one I've ever used...

If it's not on the rear of the unit it's probably lost - I've seen a few with missing S/N's. 

When I get a new piece of test equipment I usually check the fuse values.  On the K197(A) the mains fuse is only accessible with case open.  The factory fuses are glass cartridges that have a resistor in them.  I've also never seen one of these replaced.  The other fuse is the 2A fast-blow for amp-function it is assailable at the front .  Now I have seen wrong values arrive on the 2A fuse.

10A Current Function:
You may ask where is the 10A fuse but there is none on the standard K197/197A DMM's.  So I would keep this in mind should you decide to use the 10A measurement function.  I probably would find another meter to measure anything above 2A.  The K197M(ilitary) as previously mentioned does have the 10A fuse at the main board.  I also would advise against fudging in a 10A fuse on the board. 

rastro
« Last Edit: September 22, 2018, 07:51:04 pm by rastro »
 
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Offline Aleks

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Re: Keithley 197A owners' corner
« Reply #70 on: May 04, 2019, 07:47:19 pm »
Hi all,

The mailman delivered a 197A today, that I got for a bargain (32EUR). The unit has the display half working, which I thought would be an easy fix. Upon closer inspection, I've seen that the LCD zebra strips have warped and they are not making contact PCB <-> LCD any more.

I'd guess that sourcing these would be next to impossible these days, but someone might have an idea about finding some similar zebra strips?

Oh, and I can spot one bulged capacitor on my unit (on the GPIB PCB), so, maybe that would be a first in this thread :-)

Cheers!
 

Offline Aleks

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Re: Keithley 197A owners' corner
« Reply #71 on: May 04, 2019, 09:55:03 pm »
Luckily after a second look, it turned out that the zebra strips were not (maybe the only?) problem! For some reason, the underlying EL strip (which was dead) was placed at an angle, so it was obstructing the LCD plastic bezel in making contact with the PCB. This in turn did not let the zebra strip mate with the PCB on the upper left side of the LCD.

The fix: I removed the EL strip, would be making a fix with a generic EL strip from fleabay, for starters, then I saw that due to the stress that was present on the LCD, the black/gray paper filler inside the plastic bezel was indented. In order to fill up the space I made a spacer with some sticky notes that I cut in the shape of the bezel plastic. I used sticky notes so that I can remove layer by layer until I find the optimum pressure.

After reassembling the LCD, I was greeted with all zeros on the display! To verify I kept pressing the "dB" button while powering up the meter and saw that all segments were working!

Next would be for me to replace the bulged cap, hunt for a EL replacement and verify/calibrate the thing.

The 197A will make a nice addition to my bench, next or on top of my Keithley 199
 

Offline tooki

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Re: Keithley 197A owners' corner
« Reply #72 on: May 05, 2019, 06:54:49 am »
Nice!

This reminds me, I really should get back onto my project of designing a replacement display PCB for these, since a bright LED or OLED display would be so much easier to read. I've already tested the arduino code others have written to decode the data bus to the display, and it works fine, so it really is just down to actually designing a display board...
 

Offline Aleks

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Re: Keithley 197A owners' corner
« Reply #73 on: May 05, 2019, 11:38:17 am »
I've read couple of posts regarding that, hope that you find time for it! I saw a post dating from 2014 about member timb finding an OLED display that is the same size as the original LCD, was the display/part number ever found ?

 

Offline tooki

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Re: Keithley 197A owners' corner
« Reply #74 on: May 06, 2019, 12:11:47 pm »
I don't think he ever replied. :(
 


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