Paul B on sun 20 mar 05
I know i've seen this topic come up before but don't recall what the answer
is. Mine is doing that thing where it seems to work fine while firing, but
as soon as the kiln cools all the way down it reads a blank. I believe the
last time this happened, several years ago, i just replaced the
thermocouple; but i think what happens is that it seperates at the tip, and
fuses back together when hot.
Does anyone know if this thing can be brazed back together somehow so it
works all the time?
thanks,
Paul
BobWicks@AOL.COM on sun 20 mar 05
Paul:
Before you try to weld the tip of the pyrometer probe, I would suggest that
you steel wool the parts that connect to the meter. Then I would suggest that
you check the probe for continuity using a VOM. When your kiln cools down it
is doubtful if there will be a temperature reading, unless you have heat in
the vicinity of 50 to 100 degrees F. These meters are not very sensitive at
lower temperatures.
Bob
Bob Masta on mon 21 mar 05
Paul:
Your experience with the thermocouple failing on cool-down
sounds like what I have seen. If you remove the thermocouple
from the tube so you can see the weld, I think you will have
your answer. In my case (using small-gage wire TCs) the
wires get oxidized and become brittle like chow-mein noodles.
No hope of repair. You have to go way back to good metal
before you even think about re-welding. If you have spare
thermocouple wire on hand, it may be possible to weld your
own. (Don't braze.)
I have welded these using a car battery, jumper cables, and
the carbon rod from an old non-alkaline D-cell battery.
Wear safety goggles, just in case there is spatter.
You don't need a tint or anything, there is no serious arc.
Clamp the two far ends of the jumpers to a board or
some other insulator to keep them from shorting while you connect
the other two ends to the car battery. Twist the ends
of the thermocouple wire to be welded and grip
them a bit below the twisted part with one jumper clamp.
Grip the carbon rod with the other clamp. Then gently
bring the twisted junction to the rod; sometimes a wiping
action works best. The TC wire will get bright and melt
into a little ball when you get it right.
Best regards,
Bob Masta
potsATdaqartaDOTcom
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