Hi Penny--

I concur with Paul.  (I've always wanted to concur)  You can get copper 
or tin coated copper pin terminal or wire ferrule from a general 
supplier, e.g. McMaster-Carr.  I went with the pin terminal style when I 
fixed mine.

Get your mulitmeter out, and make sure there is connectivity (0/low 
resistance) between the two sides (power off, and disconnect the leads 
if you can.) at the terminal block.  My heating elements tend to die 
shortly after jumping up the voltage, so check that if there is a 
problem (you'll need to scratch off the top layer on the silicone 
carbide element to get a good measure of connectivity).  You can also 
have problem with the collar losing contact with the heating element--so 
double check that connection on both sides.  It may just need a 
cleaning--and I've been known to add a piece of foil to improve contact 
if needed.

The thermocouple can also be checked with the multimeter for 
connectivity.  If it work at low temps, then max out and maybe bounce 
around when the system warms up--there's probably a crack in it--so 
connectivity is fine until it warms up, then there's intermittent 
contact. The behavior is pretty indicative of the problem, but if you 
pull it out, you might see the crack at the tip.  You know, it's not too 
bad to have a spare thermocouple.

One other item that might be due to give out is the solid state relay 
(right side, bottom left, covered by cooling fins).  We replaced ours 
when it died with a crydom D2440 from DigiKey (double check that).  The 
pressure transducer will cut power if the system doesn't have enough He 
pressure--a great safety feature, but remember that with checking 
voltages on a live system (and be careful).

If you can have your local shop mill a new collar (the macor insulating 
collar and the brass contacts) while the system is down, that would be 
useful later on.  And get some extra metric machine screws at different 
lengths too.


Some of this is already on the Isogeochem wiki: 
http://isogeochem.wikispaces.com/TC_EA

Heating elements can be found at a number of suppliers: 
http://earth.geology.yale.edu/escsis/ESCSIS-web5.html#at
They may or may not have certain restrictions, e.g. min order or OEM 
only--and that can change.  They run a few hundred dollars each, and we 
followed the Utah gang's lead and went with Kanthar Global (thanks 
guys--and alex and mark and...).

take care

gerry


Paul Eby wrote:
> Looking at the picture, you definitely want to clean up the wiring. It 
> would appear that there is a risk of the two leads shorting out, and 
> the degree to which the leads have corroded could cause a higher 
> resistance for the electrical circuit.
>
> Paul
>
>
> At 09:58 AM 01/12/2008, you wrote:
>> Penny,
>>
>> Before replacing the switch, you definitely want to check the 
>> element. If a wire lead was loose, that could also be it. You can 
>> check the resistance across the terminals, or after removing the 
>> leads and the thermocouple, pull the element right out to visually 
>> check.
>>
>> If the element is the problem, I can advise on how to replace. If the 
>> insulation on the wiring is crumbling, you should probably replace 
>> it....
>>
>> Paul Eby
>> University of Victoria
>>
>>
>> At 09:46 AM 01/12/2008, you wrote:
>>> Hi all,
>>>
>>> I'm working hard to promote my deep, deep dislike of the TC/EA. So I 
>>> have a new problem I'd like to have your help with.
>>>
>>> The background:
>>>
>>> Probably more than a month ago now we most recently shut down the 
>>> TC/EA after a series of analyses of water for hydrogen isotopes. 
>>> Alas, I was not present during the power down (that'll never happen 
>>> again!), but am told that at about 500 degrees C the system cooled 
>>> rapidly, and the student in the lab simply shut off the power and 
>>> stopped helium flow to the TC/EA. This I suspect is related to a 
>>> crack that developed in the ceramic reactor tube that I discovered 
>>> later when taking the TC/EA apart. This has happened before with no 
>>> long-term ill effect to the TC/EA.
>>>
>>> This morning I tried to power up again for another set of water 
>>> analyses. There's a brand new reactor in the TC/EA and everything is 
>>> leak-tight. Ordinarily at this point, I just turn on the TC/EA and 
>>> warm it slowly to the full temperature that we use to water 
>>> analyses: 1450 degrees C.
>>>
>>> I did recently shift the jumper on the transformer to higher 
>>> voltage, because the TC/EA was having difficulty getting all the way 
>>> to 1450.
>>>
>>> The problem:
>>>
>>> The furnace is not warming up. The CG oven is warming fine. I've 
>>> switched on and off the system and rechecked for leaks with no 
>>> change. I moved the jumper back to where it had been with no effect. 
>>> The trouble-shooting guide only offers the further suggestion that 
>>> it could be a bad thermo-element switch. I took the aluminum cover 
>>> off the furnace to see what I could see.
>>>
>>> The questions:
>>>
>>> 1) Is there a visual way to tell if this thermo-element switch is 
>>> bad? Or do I just order a new one and hope for the best?
>>>
>>> 2) Is it possible that the heating element itself is broken? Is 
>>> there a simple way I can determine that? Where/who is a good 
>>> supplier for an element should I need to buy another?
>>>
>>> 3) This is what I saw when I took the cover off (see photo at: 
>>> http://www.earth.rochester.edu/SIREAL/Files/TC_EA_Hell.html). The 
>>> insulation crumbles if I so much as look at it and the blue wire was 
>>> not fully seated in the screw holder. Could this be the source of my 
>>> trouble? Obviously, a repair is needing and I don't want to do a bad 
>>> repair here. Any suggestions?
>>>
>>> Thanks for all your help, everyone!
>>>
>>> ~Penny
>>>
>>>
>>> *******************************************************************
>>>                       Dr. Pennilyn Higgins
>>>                        Research Associate
>>>
>>>                             "SIREAL"
>>>   Stable Isotope Ratios in the Environment Analytical Laboratory
>>>
>>>         Department of Earth and Environmental Sciences
>>>         University of Rochester
>>>         227 Hutchison Hall
>>>         Rochester, NY 14627
>>>
>>>                    [log in to unmask]
>>>
>>> Office: 209b Hutchison Hall               Lab: 209 Hutchison Hall
>>> Voice : (585) 275-0601              Outer lab: (585) 273-1405
>>> FAX   : (585) 244-5689              Inner lab: (585) 273-1397
>>>
>>>           http://www.earth.rochester.edu/SIREAL/index.html
>>> *******************************************************************
>>>
>>>
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>>
>>
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>