Keitley 238 restoration

[JxR]

There is Firmware rev A06 installed, is this the latest release?
Would be nice if you could tell what revs there are (it tells fw rev on power up).

I have attached the A10 firmware for the Keithley 238 to this post.  This firmware was pulled from my own unit.  I do think A10 is the latest FW, although I'm not 100% sure.

[leighcorrigall]

Seems there are no hi-res pictures of 238, attached a collection of my 90s 238.

Hi MiDi,

Could you please do me a favour and identify a capacitor on your digital board for me? I labelled the location on the attached picture.

My guess is that it is a 0.01 uF capacity (20 %, 50 V, CERAMIC) as noted in the Keithley 236/7 service manual parts list. The broken capacitor on my board does not have signs of a label and I do not have a service manual for the Keithley 238 with schematics. 

Thanks!

[MiDi]

According to 236/237 service manual with schematics all those caps are 10nF 50V ceramic - C35 is connected to U12 7130SA100P.
The digital part of 238 should be same as 236/7.
Those are decoupling caps, if one is removed it should not affect function of unit.

[leighcorrigall]

There is Firmware rev A06 installed, is this the latest release?
Would be nice if you could tell what revs there are (it tells fw rev on power up).

I have attached the A10 firmware for the Keithley 238 to this post.  This firmware was pulled from my own unit.  I do think A10 is the latest FW, although I'm not 100% sure.

Can anyone else verify that this firmware is working? I uploaded the EPROM firmware and all it has done is showed random lights on the front panel and killed my calibration constants. What settings do I need to apply to the EPROM programmer?

I have already transferred the original A06 firmware to the new EPROM chips, but I can't seem to use the A10 firmware that JxR has uploaded. What is going on? Any help would be most appreciated.

[JxR]

There is Firmware rev A06 installed, is this the latest release?
Would be nice if you could tell what revs there are (it tells fw rev on power up).

I have attached the A10 firmware for the Keithley 238 to this post.  This firmware was pulled from my own unit.  I do think A10 is the latest FW, although I'm not 100% sure.

Can anyone else verify that this firmware is working? I uploaded the EPROM firmware and all it has done is showed random lights on the front panel and killed my calibration constants. What settings do I need to apply to the EPROM programmer?

I have already transferred the original A06 firmware to the new EPROM chips, but I can't seem to use the A10 firmware that JxR has uploaded. What is going on? Any help would be most appreciated.

Is it possible you uploaded the two different firmware files to the wrong eproms?  801 is near the fan, while 800 is closer to the middle of the board.

[leighcorrigall]

There is Firmware rev A06 installed, is this the latest release?
Would be nice if you could tell what revs there are (it tells fw rev on power up).

I have attached the A10 firmware for the Keithley 238 to this post.  This firmware was pulled from my own unit.  I do think A10 is the latest FW, although I'm not 100% sure.

Can anyone else verify that this firmware is working? I uploaded the EPROM firmware and all it has done is showed random lights on the front panel and killed my calibration constants. What settings do I need to apply to the EPROM programmer?

I have already transferred the original A06 firmware to the new EPROM chips, but I can't seem to use the A10 firmware that JxR has uploaded. What is going on? Any help would be most appreciated.

Is it possible you uploaded the two different firmware files to the wrong eproms?  801 is near the fan, while 800 is closer to the middle of the board.

Hi JxR,

Thank you for your reply. I took pictures before and after the EPROM replacement. The 800 is located closer to the front which is an AM27C256-120DC (the notch points outwards to the case), whereas the 801 is located near the transformer which is an AM27C512-120DC (the notch points towards the transformer or inward). I copied the 238-800-A06 firmware to the new EPROM with success, so it shouldn't be about positioning. I tried to install the A10 firmware 3 times unsuccessfully. The same random display lights occurred each time. I also tried removing the battery and cycling the power supply to see if that would do anything. The EPROM programmer I used is a GQ-4X4 V4.

On another note, I have another Keithley 238 with the A10 firmware. Is it possible to copy the firmware without losing the calibration constants? Otherwise, if you have a copy of the A10, could you please email it to me?

Regards.

[JxR]

There is Firmware rev A06 installed, is this the latest release?
Would be nice if you could tell what revs there are (it tells fw rev on power up).

I have attached the A10 firmware for the Keithley 238 to this post.  This firmware was pulled from my own unit.  I do think A10 is the latest FW, although I'm not 100% sure.

Can anyone else verify that this firmware is working? I uploaded the EPROM firmware and all it has done is showed random lights on the front panel and killed my calibration constants. What settings do I need to apply to the EPROM programmer?

I have already transferred the original A06 firmware to the new EPROM chips, but I can't seem to use the A10 firmware that JxR has uploaded. What is going on? Any help would be most appreciated.

Is it possible you uploaded the two different firmware files to the wrong eproms?  801 is near the fan, while 800 is closer to the middle of the board.

Hi JxR,

Thank you for your reply. I took pictures before and after the EPROM replacement. The 800 is located closer to the front which is an AM27C256-120DC (the notch points outwards to the case), whereas the 801 is located near the transformer which is an AM27C512-120DC (the notch points towards the transformer or inward). I copied the 238-800-A06 firmware to the new EPROM with success, so it shouldn't be about positioning. I tried to install the A10 firmware 3 times unsuccessfully. The same random display lights occurred each time. I also tried removing the battery and cycling the power supply to see if that would do anything. The EPROM programmer I used as a GQ-4X4 V4.

On another note, I have another Keithley 238 with the A10 firmware. Is it possible to copy the firmware without losing the calibration constants? Otherwise, if you have a copy of the A10, could you please email it to me?

Regards.

The only copy I have of the A10 firmware is already posted above.  That was from my own unit.  I haven't had a need to look into where the calibration constants are stored, so I just don't know for sure.

I verified the firmware matched the transferred version when I performed the copy, although I haven't had a need to ever re-flash my own unit.  The 238 is kind of a PIA to calibrate.  If I had working firmware and the calibration was already good I would probably leave it alone.

The firmware has been downloaded a number of times, so hopefully someone here can confirm if they used it.

[leighcorrigall]

There is Firmware rev A06 installed, is this the latest release?
Would be nice if you could tell what revs there are (it tells fw rev on power up).

I have attached the A10 firmware for the Keithley 238 to this post.  This firmware was pulled from my own unit.  I do think A10 is the latest FW, although I'm not 100% sure.

Can anyone else verify that this firmware is working? I uploaded the EPROM firmware and all it has done is showed random lights on the front panel and killed my calibration constants. What settings do I need to apply to the EPROM programmer?

I have already transferred the original A06 firmware to the new EPROM chips, but I can't seem to use the A10 firmware that JxR has uploaded. What is going on? Any help would be most appreciated.

Is it possible you uploaded the two different firmware files to the wrong eproms?  801 is near the fan, while 800 is closer to the middle of the board.

Hi JxR,

Thank you for your reply. I took pictures before and after the EPROM replacement. The 800 is located closer to the front which is an AM27C256-120DC (the notch points outwards to the case), whereas the 801 is located near the transformer which is an AM27C512-120DC (the notch points towards the transformer or inward). I copied the 238-800-A06 firmware to the new EPROM with success, so it shouldn't be about positioning. I tried to install the A10 firmware 3 times unsuccessfully. The same random display lights occurred each time. I also tried removing the battery and cycling the power supply to see if that would do anything. The EPROM programmer I used as a GQ-4X4 V4.

On another note, I have another Keithley 238 with the A10 firmware. Is it possible to copy the firmware without losing the calibration constants? Otherwise, if you have a copy of the A10, could you please email it to me?

Regards.

The only copy I have of the A10 firmware is already posted above.  That was from my own unit.  I haven't had a need to look into where the calibration constants are stored, so I just don't know for sure.

I verified the firmware matched the transferred version when I performed the copy, although I haven't had a need to ever re-flash my own unit.  The 238 is kind of a PIA to calibrate.  If I had working firmware and the calibration was already good I would probably leave it alone.

The firmware has been downloaded a number of times, so hopefully, someone here can confirm if they used it.

According to the service manual, calibration constants are stored on the chip labelled 'LSI-83'. It is a little too late to leave things alone as I have already invested in an EPROM programmer, new chips, and the firmware posted has somehow corrupted my calibrations. I have to recalibrate now. Before I do this, I wanted to upgrade so it was not such a loss. Hopefully, someone who has already downloaded your firmware can confirm whether it works.

[JxR]

There is Firmware rev A06 installed, is this the latest release?
Would be nice if you could tell what revs there are (it tells fw rev on power up).

I have attached the A10 firmware for the Keithley 238 to this post.  This firmware was pulled from my own unit.  I do think A10 is the latest FW, although I'm not 100% sure.

Can anyone else verify that this firmware is working? I uploaded the EPROM firmware and all it has done is showed random lights on the front panel and killed my calibration constants. What settings do I need to apply to the EPROM programmer?

I have already transferred the original A06 firmware to the new EPROM chips, but I can't seem to use the A10 firmware that JxR has uploaded. What is going on? Any help would be most appreciated.

Is it possible you uploaded the two different firmware files to the wrong eproms?  801 is near the fan, while 800 is closer to the middle of the board.

Hi JxR,

Thank you for your reply. I took pictures before and after the EPROM replacement. The 800 is located closer to the front which is an AM27C256-120DC (the notch points outwards to the case), whereas the 801 is located near the transformer which is an AM27C512-120DC (the notch points towards the transformer or inward). I copied the 238-800-A06 firmware to the new EPROM with success, so it shouldn't be about positioning. I tried to install the A10 firmware 3 times unsuccessfully. The same random display lights occurred each time. I also tried removing the battery and cycling the power supply to see if that would do anything. The EPROM programmer I used as a GQ-4X4 V4.

On another note, I have another Keithley 238 with the A10 firmware. Is it possible to copy the firmware without losing the calibration constants? Otherwise, if you have a copy of the A10, could you please email it to me?

Regards.

The only copy I have of the A10 firmware is already posted above.  That was from my own unit.  I haven't had a need to look into where the calibration constants are stored, so I just don't know for sure.

I verified the firmware matched the transferred version when I performed the copy, although I haven't had a need to ever re-flash my own unit.  The 238 is kind of a PIA to calibrate.  If I had working firmware and the calibration was already good I would probably leave it alone.

The firmware has been downloaded a number of times, so hopefully, someone here can confirm if they used it.

According to the service manual, calibration constants are stored on the chip labelled 'LSI-83'. It is a little too late to leave things alone as I have already invested in an EPROM programmer, new chips, and the firmware posted has somehow corrupted my calibrations. I have to recalibrate now. Before I do this, I wanted to upgrade so it was not such a loss. Hopefully, someone who has already downloaded your firmware can confirm whether it works.

You mentioned you have a working 238 already on A10.  Why not just copy its firmware?  I would be interested in knowing if you find something wrong with the firmware I posted if you can validate it against your own.  But, the validation check out when I originally copied it, so I don't have a reason to suspect a problem. 

Also, I honestly don't know if Keithely made any hardware changes between A06-A10 that would cause an issue.  The service manual for the 238 doesn't even contain the schematic like the 236, nor does it contain any revision changes I saw.

[leighcorrigall]

There is Firmware rev A06 installed, is this the latest release?
Would be nice if you could tell what revs there are (it tells fw rev on power up).

I have attached the A10 firmware for the Keithley 238 to this post.  This firmware was pulled from my own unit.  I do think A10 is the latest FW, although I'm not 100% sure.

Can anyone else verify that this firmware is working? I uploaded the EPROM firmware and all it has done is showed random lights on the front panel and killed my calibration constants. What settings do I need to apply to the EPROM programmer?

I have already transferred the original A06 firmware to the new EPROM chips, but I can't seem to use the A10 firmware that JxR has uploaded. What is going on? Any help would be most appreciated.

Is it possible you uploaded the two different firmware files to the wrong eproms?  801 is near the fan, while 800 is closer to the middle of the board.

Hi JxR,

Thank you for your reply. I took pictures before and after the EPROM replacement. The 800 is located closer to the front which is an AM27C256-120DC (the notch points outwards to the case), whereas the 801 is located near the transformer which is an AM27C512-120DC (the notch points towards the transformer or inward). I copied the 238-800-A06 firmware to the new EPROM with success, so it shouldn't be about positioning. I tried to install the A10 firmware 3 times unsuccessfully. The same random display lights occurred each time. I also tried removing the battery and cycling the power supply to see if that would do anything. The EPROM programmer I used as a GQ-4X4 V4.

On another note, I have another Keithley 238 with the A10 firmware. Is it possible to copy the firmware without losing the calibration constants? Otherwise, if you have a copy of the A10, could you please email it to me?

Regards.

The only copy I have of the A10 firmware is already posted above.  That was from my own unit.  I haven't had a need to look into where the calibration constants are stored, so I just don't know for sure.

I verified the firmware matched the transferred version when I performed the copy, although I haven't had a need to ever re-flash my own unit.  The 238 is kind of a PIA to calibrate.  If I had working firmware and the calibration was already good I would probably leave it alone.

The firmware has been downloaded a number of times, so hopefully, someone here can confirm if they used it.

According to the service manual, calibration constants are stored on the chip labelled 'LSI-83'. It is a little too late to leave things alone as I have already invested in an EPROM programmer, new chips, and the firmware posted has somehow corrupted my calibrations. I have to recalibrate now. Before I do this, I wanted to upgrade so it was not such a loss. Hopefully, someone who has already downloaded your firmware can confirm whether it works.

You mentioned you have a working 238 already on A10.  Why not just copy its firmware?  I would be interested in knowing if you find something wrong with the firmware I posted if you can validate it against your own.  But, the validation check out when I originally copied it, so I don't have a reason to suspect a problem. 

Also, I honestly know if Keithely made any hardware changes between A06-A10 that would cause an issue.  The service manual for the 238 doesn't even contain the schematic like the 236, nor does it contain any revision changes I saw.

I cannot risk corrupting the calibration constants of another Keithley 238 that has just been professionally calibrated. This is why I am trying to get another copy of the firmware. As for the A06 to A10 update, I cannot be certain if there are any hardware changes. The differences must be subtle because I never noticed. The board material is definitely different, but the layout looks identical.

[JxR]

Did another dump on the 238 A10 EPROMS.  Welcome to see if it makes a difference.

[leighcorrigall]

Did another dump on the 238 A10 EPROMS.  Welcome to see if it makes a difference.

JxR,

Thank you so much for going out of your way! I will look it over shortly.

Were you able to copy the firmware without corrupting your calibration constants?

Regards.

[JxR]

Did another dump on the 238 A10 EPROMS.  Welcome to see if it makes a difference.

JxR,

Thank you so much for going out of your way! I will look it over shortly.

Were you able to copy the firmware without corrupting your calibration constants?

Regards.

Accuracy seems normal for not being warmed up.  Since you looked up that the calibration is stored on a different chip, I think it is unlikely to affect anything.  Also the analog section is sealed off with its own covers, and I've never noticed any negative changes when physically removing just the outer case cover.

[leighcorrigall]

Did another dump on the 238 A10 EPROMS.  Welcome to see if it makes a difference.

JxR,

Thank you so much for going out of your way! I will look it over shortly.

Were you able to copy the firmware without corrupting your calibration constants?

Regards.

I checked over both firmware copies that you have uploaded, JxR. Looks like they are identical in terms of checksums. Again, I really appreciate you doing this for my benefit. I think I will keep it as a copy if ever my Keithley 238 (A10) variation firmware dies.

My guess is that my A06 hardware variation is incompatible with your A10 firmware for whatever reason. The A06 model I have is much older in appearance:
-white cabling to triax connectors from the analogue board
-different serial number tag (no barcode) and placement
-the contrast of the screen is not as good by comparison
-inner shielding is white rather than brown
-circuit boards are translucent yellow but are of higher build quality
-IC date stamps are from the mid-'80s
-the transformer lacks a model number

Without the schematics, it's anyone guess. It would be fun to try and swap out the digital boards, but I feel like I might damage something.


On a separate note, you mentioned how difficult it is to calibrate a Keithley 238. I would say otherwise. The instructions are terrible, yes, but the procedure is rather simple if you have the following equipment:
-electrometer/picoammeter (preferably with a triaxial input, but BNC works too)
-source or source measure unit of similar specifications
-digital multimeter with 6.5 or greater

3 steps:
1) 110 V to 0 uV (connect a DMM directly to the SMU with a triax cable and a triax to banana adapter in DCV mode)
2) 1 A and 100 mA (same procedure as step 1, except in DCI mode)
3) 10 mA to 0 nA (source current to an electrometer with a triax, then source the same current through the triax to the instrument to be calibrated, provide the electrometer measurement to the instrument)

I was able to complete the procedure within a day, without any previous experience. The whole thing can be done faster because I made an Excel sheet that provides step-by-step commands after entering measurements.

If you are interested, please PM me.

Regards.

[JxR]

Did another dump on the 238 A10 EPROMS.  Welcome to see if it makes a difference.

JxR,

Thank you so much for going out of your way! I will look it over shortly.

Were you able to copy the firmware without corrupting your calibration constants?

Regards.

I checked over both firmware copies that you have uploaded, JxR. Looks like they are identical in terms of checksums. Again, I really appreciate you doing this for my benefit. I think I will keep it as a copy if ever my Keithley 238 (A10) variation firmware dies.

My guess is that my A06 hardware variation is incompatible with your A10 firmware for whatever reason. The A06 model I have is much older in appearance:
-white cabling to triax connectors from the analogue board
-different serial number tag (no barcode) and placement
-the contrast of the screen is not as good by comparison
-inner shielding has is white rather than brown
-circuit boards are translucent yellow but are of higher build quality
-IC date stamps are from the mid-'80s
-the transformer lacks a model number

Without the schematics, it's anyone guess. It would be fun to try and swap out the digital boards, but I feel like I might damage something.


On a separate note, you mentioned how difficult it is to calibrate a Keithley 238. I would say otherwise. The instructions are terrible, yes, but the procedure is rather simple if you have the following equipment:
-electrometer/picoammeter (preferably with a triaxial input, but BNC works too)
-source or source measure unit of similar specifications
-digital multimeter with 6.5 or greater

3 steps:
1) 110 V to 0 uV (connect a DMM directly to the SMU with a triax cable and a triax to banana adapter in DCV mode)
2) 1 A and 100 mA (same procedure as step 1, except in DCI mode)
3) 10 mA to 0 nA (source current to an electrometer with a triax, then source the same current through the triax to the instrument to be calibrated, provide the electrometer measurement to the instrument)

I was able to complete the procedure within a day, without any previous experience. The whole thing can be done faster because I made an Excel sheet that provides step-by-step commands after entering measurements.

If you are interested, please PM me.

Regards.

Well, I technically just said it was a (PIA) pain in the ass, which I still stand by.  I certainly had no issue doing it either, but it still took quite a while.  I had an in calibration 2450 so did the entire procedure with that from what I remember.

[JxR]

So, your going to hate me but here it goes.  I'm and idiot and selected the wrong chip size when I originally copied this firmware(not once but twice).  This was discovered last week when I said, "I should get some EEPROMs and change these chips out."

I even labeled my original firmware files with the wrong chip sizes and so I of course ordered a few of those first, wasting ~$30 for NOS EEPROMs I don't have a need for (These chips are getting hard to find).  I had to dig into the K236 schematics to find out where I went wrong.  Oh, and of course I lost my calibration in the process, which is probably karma for being a dumbass.

So to be perfectly clear:

U17 or A10-800 is a 27C256 OTP.  This was replaced with an Atmel 27C256R-15 OTP.
U31 or A10-801 is a 27C512-200.  This was replaced with a Windbond W27C512-45Z.

I can 100% confirm that the files provided successfully flashed to these chips, and the K238 went through start up successfully.  Course I now have to re-calibrate it.

All I can say is sorry for wasting anyone's time who was unlucky enough to try and burn my previously posted firmware(which I removed).  I will have to wait about a month until I will have sufficient free time to re-calibrate my own unit.

Actual working firmware attached (for real this time).

[leighcorrigall]

Actual working firmware attached (for real this time).

 

I can confirm that this A10 firmware above is working on my Keithley 238. At least this correction will help members in the future.

What I am concerned about now is that xDevs.com has picked up your corrupt firmware and has added it to their website:
https://xdevs.com/doc/Keithley/238/firmware/ (WARNING: DO NOT USE THIS FIRMWARE!)

I cannot say for certain, but the filenames match your description and the sizes are also incorrect, suggesting that this is your broken firmware. You should contact them to tell them to take it down. I tried to contact them about where they got it from a while ago, but no one seemed to reply.

Thank you for being honest with everyone, JxR. You did the right thing. 

[MiDi]

Forwarded to TiN from xDevs.

[JxR]

Actual working firmware attached (for real this time).

 

I can confirm that this A10 firmware above is working on my Keithley 238. At least this correction will help members in the future.

What I am concerned about now is that xDevs.com has picked up your corrupt firmware and has added it to their website:
https://xdevs.com/doc/Keithley/238/firmware/ (WARNING: DO NOT USE THIS FIRMWARE!)

I cannot say for certain, but the filenames match your description and the sizes are also incorrect, suggesting that this is your broken firmware. You should contact them to tell them to take it down. I tried to contact them about where they got it from a while ago, but no one seemed to reply.

Thank you for being honest with everyone, JxR. You did the right thing. 

I just took care of uploading the new firmware to the xdevs ftp, with explanation to replace the old one.

Just FYI, I can't personally remove the existing firmware or place it in the normal area most people navigate to.  The upload is done based on these instructions.
https://doc.xdevs.com/contact/

[MiDi]

TiN has replaced them, should be fine now.