I've just experienced a problem with my temperature controller, a Cal
9400, and I have helped a friend with a few Cal 9500P with the same
problem from time to time, basically sporadic behaviour and erroneous
temperature readings or thermocouple failure indication. I know the
problem is related to the classic problem of solder or tin plated
contacts oxidising as I was aware that the guts of these controllers can
be pulled from the panel mount by design to allow hot swapping such as
when one goes down in a large bank as in an extruder line, it saves
having to access the back of the board and removing and replacing wires
when the electronics can be easily changed from the front. I just pulled
mine and put it back and it's going correctly again as that action wipes
the contact surface. Now I'm wondering if there is some suitable contact
sealant or protective coating that I can apply to the contacts to
prevent this happening again, the environment isn't hot or damp in my
case but this problem comes up from time to time, my friend now pulls
her's as part of the yearly workshop service. I have seen dielectric
grease which seems like it might do the job but it needs to be something
which won't effect the low currents in the thermocouple. Any suggestions
would be appreciated. BTW I know of another kiln that is suffering the
same sort of issue with one thermocouple reading low and tightening the
screws helped for a few weeks but it's back but I haven't been able to
check as it was being used and the 2nd thermocouple seemed OK, in that
kiln the thermocouple connection is next to the case so will get hot in
use so if anything is available then maybe 100C capability or higher
would be good for the 2nd application.

On Wednesday, October 1, 2014 1:17:18 PM UTC-7, David Billington wrote:
I've just experienced a problem with my temperature controller, a Cal
9400, ... sporadic behaviour and erroneous
temperature readings or thermocouple failure indication.

...same sort of issue with one thermocouple reading low and tightening the
screws helped for a few weeks but it's back

Thermocouple failure is tested with a resistance check, and eventually thermocouples
DO age and die (if you can uncouple the thermocouple from the meter, and
measure its resistance with an ohmmeter, you can match the resistance
you measure with the controller's specified maximum ohms value).

If the resistance is from corrosion/age, you need to replace the thermocouple.

If it's the resistance at a screw-down spot, this can be improved by welding the
thermocouple wire to a washer (or lug), and screwing down the lug with
a star-type lockwasher under it. The little points that dig in make a
gas-tight metal/metal connection that doesn't get 'loose'.

If the problem is in protected connectors (that don't get dusty or wet) inside a
protective housing, you might try contact enhancers like

http://www.radioshack.com/product/index.jsp?productId=29392326

after a little compressed-air dusting and maybe a wipe with an alcohol-soaked swab.

"David Billington" wrote in message
...
...I know the problem is related to the classic problem of solder or
tin plated contacts oxidising ...

You prompted me to test the insulation strength of this:
http://www.gardnerbender.com/en/ox-100b
which is a grease mixed with conductive particles of zinc and
graphite. I've been experimenting with it to repair contacts in old
instruments and vehicles that I can't disassemble to polish with an
ink eraser.

The fixture is two sheet aluminum cutoffs from under the shear. I
covered one with two parallel strips of Scotch tape about 1mm apart,
smeared Ox-Gard along the gap and taped the other over it. The tape is
0.0045" thick in two layers (to avoid adhesive on the mike anvil).

My analog, hand-cranked 1KV Megger correctly shows the ratio between
applied voltage and leakage current (= resistance) regardless of the
cranking speed. At low speed it read above 800 Megohms. The meter
showed ~200VDC on the Guard terminal when the grease started to break
down. I don't know how closely Guard matches the Sense voltage. The
resistance reading dropped below the 10 Megs of a DVM at around
300-400VDC.

In other words that brief test shows it's promising, the metal
particles don't short together at low voltages. I think the
dissimilar-metal voltages in a thermocouple connection would cancel as
long as both terminals are at the same temperature.

-jsw

"whit3rd" wrote in message
...
On Wednesday, October 1, 2014 1:17:18 PM UTC-7, David Billington
wrote:
I've just experienced a problem with my temperature controller, a
Cal
9400, ... sporadic behaviour and erroneous
temperature readings or thermocouple failure indication.

...same sort of issue with one thermocouple reading low and
tightening the
screws helped for a few weeks but it's back

Thermocouple failure is tested with a resistance check, and
eventually thermocouples
DO age and die (if you can uncouple the thermocouple from the meter,
and
measure its resistance with an ohmmeter, you can match the
resistance
you measure with the controller's specified maximum ohms value).

If the resistance is from corrosion/age, you need to replace the
thermocouple.

If it's the resistance at a screw-down spot, this can be improved by
welding the
thermocouple wire to a washer (or lug), and screwing down the lug
with
a star-type lockwasher under it. The little points that dig in make
a
gas-tight metal/metal connection that doesn't get 'loose'.


You can buy spade lugs made of thermocouple alloy:
http://www.omega.com/pptst/TL_SL_BSJ.html

I use red and yellow nail polish to mark K thermocouple ends and
terminals. It doesn't withstand much heat. Wood stove gasket cement
keeps the braid from unraveling to at least 2000F.
-jsw

On Wednesday, October 1, 2014 4:17:18 PM UTC-4, David Billington wrote:
I've just experienced a problem with my temperature controller, a Cal

9400, I know the

problem is related to the classic problem of solder or tin plated

contacts oxidising I have seen dielectric

grease which seems like it might do the job but it needs to be something

which won't effect the low currents in the thermocouple. Any suggestions

would be appreciated.

Try looking up fretting corrosion. There is a lot of history on this type of problem.

One early remedy was microcrystalline Wax in mineral oil. Another remedy is Cramolin. www.caig.com It works well, but the techs did not like it as it smelled. They much preferred Gold Mist.

Dan

On 10/1/2014 6:32 PM, Jim Wilkins wrote:
"whit3rd" wrote in message
...
On Wednesday, October 1, 2014 1:17:18 PM UTC-7, David Billington
wrote:
I've just experienced a problem with my temperature controller, a
Cal
9400, ... sporadic behaviour and erroneous
temperature readings or thermocouple failure indication.

...same sort of issue with one thermocouple reading low and
tightening the
screws helped for a few weeks but it's back

Thermocouple failure is tested with a resistance check, and
eventually thermocouples
DO age and die (if you can uncouple the thermocouple from the meter,
and
measure its resistance with an ohmmeter, you can match the
resistance
you measure with the controller's specified maximum ohms value).

If the resistance is from corrosion/age, you need to replace the
thermocouple.

If it's the resistance at a screw-down spot, this can be improved by
welding the
thermocouple wire to a washer (or lug), and screwing down the lug
with
a star-type lockwasher under it. The little points that dig in make
a
gas-tight metal/metal connection that doesn't get 'loose'.


You can buy spade lugs made of thermocouple alloy:
http://www.omega.com/pptst/TL_SL_BSJ.html

I use red and yellow nail polish to mark K thermocouple ends and
terminals. It doesn't withstand much heat. Wood stove gasket cement
keeps the braid from unraveling to at least 2000F.
-jsw


There is a fortified RED gasket RTV that is up to 6or 7000F as I recall.
The standard would burn out in my wood stove every other year. Once I
put on the RED with a new fiberglass rope it lasted longer than 5. I
sold the house at 5 so I don't know if they trashed the wonderful stove
or use it another 17 years.

Martin

On 2014-10-01, David Billington wrote:
I've just experienced a problem with my temperature controller, a Cal
9400, and I have helped a friend with a few Cal 9500P with the same
problem from time to time, basically sporadic behaviour and erroneous
temperature readings or thermocouple failure indication. I know the
problem is related to the classic problem of solder or tin plated
contacts oxidising as I was aware that the guts of these controllers can
be pulled from the panel mount by design to allow hot swapping such as
when one goes down in a large bank as in an extruder line, it saves
having to access the back of the board and removing and replacing wires
when the electronics can be easily changed from the front. I just pulled
mine and put it back and it's going correctly again as that action wipes
the contact surface. Now I'm wondering if there is some suitable contact
sealant or protective coating that I can apply to the contacts to
prevent this happening again, the environment isn't hot or damp in my
case but this problem comes up from time to time, my friend now pulls
her's as part of the yearly workshop service.

My own personal favorite was something called Cramolin, which
got replaced by DeOxit (same company, but less ozone-depleting chemicals
in the propellant). Looks like they have been going through more name
changes -- but everything from this company is *very* good for contact
cleaning and preservation. This is not a company website, but someone's
review and experience.

http://www.siber-sonic.com/electronics/caig.html

Good Luck,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 2014-10-02, wrote:
On Wednesday, October 1, 2014 4:17:18 PM UTC-4, David Billington wrote:
I've just experienced a problem with my temperature controller, a Cal

One early remedy was microcrystalline Wax in mineral oil. Another
remedy is Cramolin. www.caig.com It works well, but the techs did not
like it as it smelled. They much preferred Gold Mist.

Yes -- the Cramolin smelled toxic -- the DeOxit a bit less so,
and apparently they have a mix of new chemicals from the same company.
I just posted a link to a review of sorts which discusses the name
change game. :-) But I did use Cramolin in spite of the smell -- it was
*that* good.

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 02/10/14 05:21, DoN. Nichols wrote:
On 2014-10-01, David Billington wrote:
I've just experienced a problem with my temperature controller, a Cal
9400, and I have helped a friend with a few Cal 9500P with the same
problem from time to time, basically sporadic behaviour and erroneous
temperature readings or thermocouple failure indication. I know the
problem is related to the classic problem of solder or tin plated
contacts oxidising as I was aware that the guts of these controllers can
be pulled from the panel mount by design to allow hot swapping such as
when one goes down in a large bank as in an extruder line, it saves
having to access the back of the board and removing and replacing wires
when the electronics can be easily changed from the front. I just pulled
mine and put it back and it's going correctly again as that action wipes
the contact surface. Now I'm wondering if there is some suitable contact
sealant or protective coating that I can apply to the contacts to
prevent this happening again, the environment isn't hot or damp in my
case but this problem comes up from time to time, my friend now pulls
her's as part of the yearly workshop service.
My own personal favorite was something called Cramolin, which
got replaced by DeOxit (same company, but less ozone-depleting chemicals
in the propellant). Looks like they have been going through more name
changes -- but everything from this company is *very* good for contact
cleaning and preservation. This is not a company website, but someone's
review and experience.

http://www.siber-sonic.com/electronics/caig.html

Good Luck,
DoN.

Thanks for the advice. In the end I found a UK seller on ebay that sold
a 4 pack of 2ml Deoxit tubes
http://www.ebay.co.uk/itm/Deoxit-Squ...-/121275842502
so I've ordered that and will see what happens. The 4 pack contains all
that would seem to be required for cleaning and protection so if it
works I may report back in a decade or so, if not much sooner.

On 2014-10-02, David Billington wrote:
On 02/10/14 05:21, DoN. Nichols wrote:
On 2014-10-01, David Billington wrote:
I've just experienced a problem with my temperature controller, a Cal
9400, and I have helped a friend with a few Cal 9500P with the same

[ ... ]

My own personal favorite was something called Cramolin, which
got replaced by DeOxit (same company, but less ozone-depleting chemicals
in the propellant). Looks like they have been going through more name
changes -- but everything from this company is *very* good for contact
cleaning and preservation. This is not a company website, but someone's
review and experience.

http://www.siber-sonic.com/electronics/caig.html

Good Luck,
DoN.

Thanks for the advice. In the end I found a UK seller on ebay that sold
a 4 pack of 2ml Deoxit tubes

http://www.ebay.co.uk/itm/Deoxit-Squ...-/121275842502

so I've ordered that and will see what happens. The 4 pack contains all
that would seem to be required for cleaning and protection so if it
works I may report back in a decade or so, if not much sooner.

Hopefully you won't have anything to report for decades. :-)

Good Luck,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

"DoN. Nichols" fired this volley in
:

http://www.ebay.co.uk/itm/Deoxit-Squ...-Kit-4-2mL-tub
es-of-clean-and-protect-products-/121275842502

so I've ordered that and will see what happens. The 4 pack contains
all that would seem to be required for cleaning and protection so if
it works I may report back in a decade or so, if not much sooner.

Hopefully you won't have anything to report for decades. :-)

Good Luck,
DoN.


For decades in our computer shop, we used an AMP product. It was just a
'numbered' stock item, in a quart metal can. One can would last our
whole shop (six to ten techs) a year. It was a slightly oily liquid that
smelled of nitrobenzene. It cleaned, and left the merest of residues
which both shielded against oxidation and lubricated board-edge finger
connectors. That helped prevent the major difficulty with those, which
was not oxidization, but fretting corrosion due to vibration. (Big
boards, 200 fingers, each.)

Lloyd

On 2 Oct 2014 04:27:42 GMT, "DoN. Nichols"
wrote:

On 2014-10-02, wrote:
On Wednesday, October 1, 2014 4:17:18 PM UTC-4, David Billington wrote:
I've just experienced a problem with my temperature controller, a Cal

One early remedy was microcrystalline Wax in mineral oil. Another
remedy is Cramolin. www.caig.com It works well, but the techs did not
like it as it smelled. They much preferred Gold Mist.

Yes -- the Cramolin smelled toxic -- the DeOxit a bit less so,
and apparently they have a mix of new chemicals from the same company.
I just posted a link to a review of sorts which discusses the name
change game. :-) But I did use Cramolin in spite of the smell -- it was
*that* good.

Enjoy,
DoN.

I agree with Don

Gunner


"At the core of liberalism is the spoiled child,
miserable, as all spoiled children are, unsatisfied,
demanding, ill-disciplined, despotic and useless.
Liberalism is a philosophy of sniveling brats."
PJ O'Rourke