Hi,
I've got about 15 response quickly after my posting about VT error problem. Many thanks to Jeff de Ropp, Robert Harker, Weixing Zhang, Andrew J. Jensen, Christopher Kirby, Richard K. Shoemaker, Margaret Eastman, Andrew Fowler, Thomas C. Dickinson, Qiuwei Xu, Shaoxiong Wu , Xiangming Kong, Julie Fisher, Edward T. Cahainani.
My original question:
"I have problem with the VT controller of my Varian INOVA 600.When I was trying to set up the temperature to 27C, the temp didn't change, and in acqstatus window it showed "VT: HW error". Then Ichecked the VT controller on the back of console. The left status LED on the front panel of VT controller (Highland L900) turned in red, which means some error. The display in control panel: STATE: ERROR, LAST ERR : HTR RES. The last item is the error message indicating " measured heater resistance is blow 2 or above 40 ohms". Could anyone tell me what's really happened to the spectrometer? ( The MAX TEMP was set at 40C)."
The responses were concentrated ontwo possibilities:
1. the probe heater is damaged
2. the cable connection problem.
After careful checking, we finally found that it was really the problem of cable connection. When we opened the plastic jacket covering the female DE-9 connector of VT cable that plugs into the probe, we found the red wire in pin 3 (connecting the constantan of T/C) was broken. Then we decided to replace the connector. When we cut all wires from the connector, we further found that the white wire from pin 6(connecting to the silver thick wire with transparent cover of the heater) was disconnected from the big wire, due to the loose soldering. Iam wondering why Varian use this kind of style of wiring. The two heater wires are very thick until they reach the female DE-9 connector, where they are replaced with two very thin wires soldered to them. This kind of connection is too easy to be broken. Anyway, after reconnecting this wire and replacing the DE-9 connector, we solved the problem.
Following are all the responses:
1. When we have had similar error messages it has meant the heater in the
probe has needed replacing. It has required sending the probe back to
Varian (in Bruker probes, at least older types, one can easily replace the
heater oneself but apparently with Varian its more complicated and you
should send the probe back). The cost has been ~2500$.
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2. The air flow is too hi or to cold on the inlet. The VT works by heating
the air or N2 gas immediately before it impacts the thermocouple in the
probe. The controller wisely monitors several items such as coil
resistance, RTD sensor and etc. The controller will continue to add current
to the coil until the temperature is reached or one of the cutoffs is found
(RTD, Coil res etc). The heater coil resistance increases with temperature
of the coil so this means it was too hot (or open) but if it was too hot
then it should have tripped the 200ohm RTD. The only way this can happen is
if the unit is very or cold.
It is possible the RTD is reading wrong from and overheated event or that
the coil is damaged but they usually open.
Smell the probe for signs of burnt electronics. Measure the RTD and coil
resistance and make sure they are in spec with the vt current off.
If it turns out to be a burnt heating coil, they are now probe repairs and
are no longer user servicable ...
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3. Have you checked the cable connection at the probe?
Have you tried the command sethw('vt','reset')?
If you have already done the above, then something might be wrong.
Good luck and wish you a happy Chinese New Year!
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4. We have had VT issues on our Varian systems before, but I do not think they are the exact ones you are having. Our problem was that the VT connector to the probe was loose, and gave false readings. You may want to check the cable connection to the probe. It tends to weaken over time.
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5. The Varian VT cables, in my experience, get 'soft' over time. Check the continuity of the whole cable (i.e. ignore the VT unit and probe). The connections to the probe are the usual problem. I've had to rebuild/fix 3 cables over my 7 years and the errors are always with the cables. Hope this is helpful.
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6. You clearly have an open circuit (or short)in the heater loop. The most
common cause of this is a broken wire in the VT-cable going to the probe. I
just had one of these apart, and I should be able to remember which pins
they are.
The same error would occur if you either melted/shorted your probe heater,
or if your heater coil broke, or if you connections between the heater and
the DB-9 connector inside the probe. This could be simple or catastrophic
probe damage, but all of this is unlikely to be the problem.
I've had to repair or replace the VT-heater/sensor cable on my Inova-400 3
times in the past 4 years. These cables (and the DB-9 connector
specifically) are infamous for being not only poorly constructed but also to
break easily (at the probe-end connector...especially if probes are changed
frequently, requiring one to disconnect/reconnect this cable frequently.
You can check the cable by checking the continuity between the VT-Controller
(I assume you have a Highland VT controller) and the Probe connector (DB-9).
PIN-OUTs for continuity checking of VT Cable:
The white connector going to the VT controller has 6 female connections, 5
of which are normally used (labeled as P1-P6 below - my numbering system).
Using standard numbering for a DB-9 connector, you can start with The
Big-Black wire (Pin-1 of the white VT-Controller connector), and check these
continuities:
VT-Controller Heater (white connector) DB-9 Pin Number
--------------------------------- ----------
Big(fat)-Black Wire (P1) Pin#-7
Big(fat)-"Clear/Silver" Wire, (P2) Pin#-6
Small Black Wire (P3) Pin#-5
Small Red Wire (P4) Pin#-8
Small Black Wire (P5) Pin#-9
No Connection (P6)
----------------------------
Temperature Sensor(Thermocouple) : Copper-Constant (copper and silver
connectors). If this were broken, your temperature reading would be "999"
so this isn't your problem. Just for completeness...
Blue Thermocouple Connector (Silver Connector) > Pin# 3 (DB-9 end)
Blue Thermocouple Connector (Copper Connector) > Pin# 1 (CB-9 end).
You can also check the heater continuity and resistance using an Ohm-Meter.
Check the resistance between Pin-6 and Pin-7 on the DB-9 connector (this is
the two left-most pins on the bottom row of 4-pins). You should see 23-25
Ohms for a normal liquids probe (3-4 Ohms for a Varian CP-MAS solids probe
heater). The other two pins on the bottom row (#8 & #9) are some kind of
return-sense connections, and usually show a resistance of around 100 Ohms.
I'll bet it's a bad connection in your DB-9 connector (i.e. a wire has
broken off or fallen out of the connector). You don't want to know how much
$$$ Varian wants for a new VT-cable assembly (I always keep a spare one on
hand, so I can use the spare while I re-build the broken one).
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7. It sounds like the connection of the cable to the probe is bad. This
connection has sometimes been faulty on our 400, in which case we see the
the temperature readout on the controller go up to +209 (while the actual
temperature remains low). I would remove the connector at the probe and
make sure it is securely connected, then type "temp" and hit the "reset VT"
button. If it is not something as simple as a temporary faulty connection,
I am not sure what is wrong.
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8. I should probably have mentioned the obvious in my last message. First
remove and inspect the VT-connector to the probe, and then re-connect it,
being absolutely sure that it's on all the way.
All of the stuff that I wrote about checking the continuity of the heater
current path assumes that a simple bad probe connection has been ruled out.
These connectors are also notorious for wiggling loose, thanks to Varian's
_wonderful_ way of connecting the DB-9 cable connector to the probe. Of
course, this has been discussed many times before.
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9. Have you checked the connection between the VT controller cable and the
probe? Make sure that's secure and then reset your VT.
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10. The VT heater monitors the probe heater resistance ( _at_ 20 ohm's) and the
thermal couple ( _at_ 110 ohm's at ambient temperature. The 9 pin connector has
four lower pins, Fril right to left, 6&7 measute the TC and 8&9 are the
heater.
A simple test is to connect another probe to the vt gas and heater cable and
see if the problem goes away. Or you can ohm out the probe connector to see
if the heater coil has opened or shorted.
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11. I saw similar messages several months ago. What I found was the crack of one
rubber tube near the probe in the VT air line. It went away once I replaced it.
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12. I had the same problem long time ago. As Rich said, double check the VT cable. Make sure
the connections are good. Then check the communication cable, make sure they are connected very well.
reboot everything. Very few VT control boards are bad.
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13. I wonder if your heater in your probe is broken. If you have another
probe, how about changing the probe to see if the heater is wrong as
the error message indicated. I checked the L900 technical manual, it
said "If Rh is below 2 or above 40 ohms, an error is declared".
May you already try: ompletely reset the VT unit and the communication
between console and host computer.
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14. We had a similar error on our inova. It turned out to be the connections to the pins on the vt cable that plugs into the probe (our machine is about 3 years old I don't know if the vt connection has changed but the controller is the same model as yours) It was straight forward for our electronics people to fix the connection. I think our problem came about as we had changed probe a few times and each time I think there had been strain on the vt connector. I hope this is the problem with yours becuase as I said it is easy to fix.
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15. Looks like you have either a shorted heating element or (more likely) a
blown (open) heating element. I say this because of the error message you
described:
> The last item is the error message indicating " measured heater
> resistance is blow 2 or above 40 ohms".
If that is the case, have the heating element checked and replaced if
necessary. Over time, the heating element (a length of nichrome wire)
becomes oxidixed and will eventually break.
It might also be that some connection to the heater might have become
loose. In this case, fixing the connection will solve the problem.
Thanks,
Xianzhong
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Xianzhong Yan, Ph.D.
NMR Laboratory, National Center of Biomed. Analysis
27 Taiping Rd., Beijing 100850 P. R. China
Phone: 86538174,66930305
Fax: +8610-68186281
E-mail: yanxz_at_nic.bmi.ac.cn
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Received on Fri Jan 27 2006 - 15:52:20 MST