Well it appears that you're correct about the Pace tweezers having a sensor.

That could be significant if you were wanting to use an Ungar handpiece on a
Pace controller.. but you're not.
The sensor doesn't prevent the operation of the heaters in the Pace
handpiece.
My apologies if I forgot to mention that heaters only require 3 wires.. and
one is for earth ground.

Finding only 3 conductors in the Ungar handpiece and no sensor leads, as
I've done, demonstrates to me that there is NO SENSOR in the Ungar
handpieces (proof enuff for me).

Buy a used Ungar handpiece if you need proof. Schematics aren't easy to
find.. the last one I got was from an Ungar distribution manager who had
access to obsolete equipment literature, and that was maybe 7 years ago.
Or, buy a Pace controller.. but you already knew that was an option.

You didn't initially state that you wanted a rational explanation of how the
Ungar controller operates, but my suggestion would've been to call
Weller/Cooper or whoever owns what's left of Ungar, and ask.

If I were going to use the Pace tweezers with the Ungar controller, I'd
connect the 3 heater leads, and experiment with a couple of values of
variable resistors at the "not sensor" compensation resistor pins pointed
out earlier.
If the controller (any controller) doesn't output a significantly greater
voltage than 24V, it's not going to destroy the tweezers.

It may be worthwhile to modify the plug for the tweezers to match the Ungar
connector in the event that you may want to use an Ungar handpiece in the
future.

It's likely that the value of the compensation resistor will be different
from the ones associated with the Ungar soldering irons, because the tweezer
heaters are different (2 heaters paralleled).
The performance of the Pace tweezers may not match the original performance
specifications of the Ungar station with the recommended Ungar soldering
irons, but it should have a fairly stable adjustable temperature when an
appropriate value for the compensation resistor is determined.

There were some high wattage irons available for the Ungar 4024 unit, for
example, but I don't know if the 9900 controllers are similar.

--
Cheers,
WB
..............


"mike" wrote in message
...
I was gonna modify the socket. I have other places to plug the iron.

Well...hate to shatter your confidence.
The info is he http://www.paceworldwide.com/sites/d...iles/TT-65.pdf
it includes a schematic showing the sensor.

Here's the troubleshooting chart for the PACE TT-65 handpiece:
Was a PDF chart that got copied as text, but you can see the
4 headers:
SYMPTOM CHECKOUT PROCEDURE CAUSE SOLUTION
No heat
Check resistance - Pin 2 to
Pin 5. Resistance should
be 10 ohms.
If not - -Open Heater

______________Here's the relevant part
Handpiece
overheating
Check resistance - Pin 3 to
Pin 6. Resistance should
be 110 ohms.
If circuit
reads less than 105 ohms - -Shorted Sensor
____________End of relevant part.

I believe that you have experience that leads you to a conclusion
that is incorrect for the systems I have.
Your conclusion seems to be contrary to all my experience. I fail
to understand how power input can change with heat load
without sensing something.

I know of three ways in use to have temperature control with two
active wires (plus safety/static ground).
I have used irons using all three methods.

1)put ALL the electronic controls in the handpiece.
2)the weller magnastat that uses a thermally activated switch in the
tip.
3)the Metcal system that pumps RF down the cable and uses a property
of material in the head to absorb the RF and heat only when below
the transition temperature of the tip.

This article describes various systems.
http://en.wikipedia.org/wiki/Soldering_iron

I obviously don't need to say this, but.. hey, don't take my word for
it.

I won't, because I haven't heard a rational explanation.
Can you describe the mechanism that allows
the power input to change based on heat flow without sensing
something.
Finding a calibration pot in the plug doesn't demonstrate that a sensor
does not exist.

You don't need an extra one. Just unplug one and take a meter to it.
The sensor in my Weller EC1301 sensor measures 27 ohms cold and about
43 ohms at 700F.
The only adjustable power supply that I own with the UNGAR name
is the aforementioned 9900AS. It has WAY MORE circuitry than
would be required for open-loop power control (light dimmer style).
The number and type of integrated circuits is consistent with
the schematics for the PACE temperature control systems.
Not having a handpiece or schematic, I can't prove it. I can only
demonstrate
that the power out is dependent on the value of a resistor plugged
into the socket...assumed to be the sensor. It appears that the
type of sensor varies much more with temperature (in the 5K to 10K region)
than the sensor
used by the PACE or Weller EC series.

Are we having fun yet?