Keithley 2000 RS-232 RTS, WTF!?!

[z01z]

May be handy to know: Keithley has a piece of software to flash your 2000 by RS-232 (maybe GPIB). Something called flash wizard 32. Of course this doesn't work due to the OTP eproms used. Yes, that took me some time, so consider this as a warning. It may work with flash chips, but I have never seen rewritable chips in older Keithley devices so I'm not sure.

The -WE pin is wired to Vcc, which means the flash can only be read in-circuit.
Even if this program you've mentioned could be used for a 2000, the new flash has to be programmed first externally anyway (otherwise the serial/GBIP communication won't work, through which the flash could be programmed)

[eas]

I'd be interested to learn if newer versions of the hardware and/or firmware have the same behavior of driving RTS/Pin 7 to a negative voltage when the DMM is powered on and the RS-232 communications are enabled.

Yes, it appears to be so. I've measured -9V on that pin with the A15 firmware.

Thanks for checking. Anyone on the A20 firmware willing to check?

[eas]

Ok, so I now have some newer K2000 hardware with A20 firmware. I just checked the voltage on RTS wrt the ground pin. 0v.

I'm not going to open it up to check for date codes and check for circuit revisions until I've had it for a couple of weeks in case I have to return it to the seller for some reason.

[Smith]

As i remember the RTS setting was an option under the RS232 menu (flow control?). Dont have an 2000 here right now, so I can't check.

[eas]

As i remember the RTS setting was an option under the RS232 menu (flow control?). Dont have an 2000 here right now, so I can't check.

The only flow control options available are "None" or Xon/Xoff." If it had an option for hardware flow control, the K2000 would be responsible for driving the CTS line, which it can't do because the second output from the level shifter is wired to the RTS pin. As for RTS, it is supposed to be controlled by the DTE (data terminal equipment, ie the PC).

[eas]

Ok, so I now have some newer K2000 hardware with A20 firmware. I just checked the voltage on RTS wrt the ground pin. 0v.

I'm not going to open it up to check for date codes and check for circuit revisions until I've had it for a couple of weeks in case I have to return it to the seller for some reason.

I finally opened it up. Looks like it was made in 2007. Board revision is copyright 2006. RTS pin is no longer hooked to the level shifter. Only pins connected to the level shifter are Rx and Tx. The other output and input pins on the level shifter doesn't seem to be connected to anything any more.

[gamalot]

My Keithley 2015 had the same problem, so I just cutted the pin 7 & 8 of ADM202 chip, now it works very well, thank you so much!

[eas]

Glad to have saved you some time and frustration!

[ve7xen]

What an infuriating problem. Spent all night trying to figure out why my K2000 was randomly crapping out while trying to do datalogging. Nominally it works, but eventually it just stops responding to :READ? requests, usually within a minute.

I cut the traces for CTS/RTS on the ADM202 and things are vastly improved but I'm still having some reliability issues. Not totally sure that it isn't my RS232 gadgets, but two different ones have similar symptoms. The meter is also not at all tolerant of spurious input either, it is often getting wedged in a state where the 'acquire' marker on the VFD is lit, but no measurement is taking place and no keypad input is accepted other than LOCAL.

Has anyone tried replacing the actual ADM202? Or maybe just its boost capacitors?

I will also see about getting myself a programmer and upgrading to A15. My meter is currently running A05.

Thanks for the good work tracking down the level shifter as the problem, I wasn't really able to get good measurements on it due to common mode crap in my lab.

[eas]

As I recall, I came across at least one person who replaced the level shifter and reported their problems were solved.

[ve7xen]

So a follow up. Received some parts today and got to work on repairing my K2000.

• Replaced all electrolytic capacitors with new, 105? 5000+ hours units
• Replaced ADM202 U159 with new MAX202 equivalent from TI
• Before installing, lifted pins 7 and 8 of MAX202 and did not solder them
• "Conditioned" the VFD @ 6.5V for a few minutes. It did help.

There was no leakage from the existing electrolytics found. I did find that last time I attempted to lift the pins I must have been drunk, as I lifted pins 6 and 7 of its neighbour, U164 which is part of the trigger input. I fixed that botched job while I was in there. Also replaced a missing screw on the linear regulator that holds the PCB in place. It is a 4-40 machine screw.

Unfortunately still no joy, it seems to be exhibiting the same symptoms as before, after some time it appears to stop responding to commands over RS232 until sent a RST* command (or maybe init or something, not sure exactly). Maybe I am doing something stupid in my script, I will fiddle around some more. I'm beginning to suspect the firmware. I ordered a programmer from China, but being the new year there, it probably won't ship for another week, so I won't get it for 2 months.

If I can't find anything in my code to get it reliable I'll do some more careful probing around and have a look at the signal integrity.

Edit: After some additional testing, it definitely appears the device 'ignores' and does not respond whatsover to a single command. The next issued command does appear to work. This looks like a bug to me. I added up to 1s of delay between commands in my code and while it does help, it still glitches after a while. I may need to add a timeout and re-send failed commands if there is no response, at least until I can test A15.

[Elmar]

So I bought a 2nd hand keithley 2000 advertised as "in good shape" turns out the rs232 was not working. Ended up being a hardware defect with the level shifter.

Instead of going through a drama with the seller and having to wait longer before I can do my measurements I just grabbed my soldering iron.  It turns out the level shifter actually had 2 more unused channels so i just switched the broken channel to the "spare" channel

Attached a picture of the mod, maybe it's useful for someone that has the same problem. Worked out great for me, rs232 works now!