> Have you traced out the schematic and can post for us?
I have uploaded a copy of the wiring diagram into the Files Section under "Laminator Mods".
I'd appreciate comments from anyone who is interested in modifying this cheap (<$25) laminator that uses bimetal thermostat switches for temp control. Ultrakeet in OZ replaces the thermal protector (fuse) with a new 250 deg. one, and swaps a new 160 deg. thermostat for one of the existing ones. My question to the group was "which one" to replace, as the CS-923 has three of them instead of two as in the Ultrakeet example.
Here's how the laminator control system works: The heater elements (connected in series with the thermal fuse) are powered from either half-wave or full-wave rectified AC line voltage, depending on temperature. At power-up, both thermal switches are closed, which provides full-wave rectified voltage to appear across the heater element. Once the temp rises to either 115 or 125 deg and the low voltage thermostat opens, one rectifier will be disconnected and the heater will only see negative half-cycles, reducing the average voltage by about one-half. When the heat rises to the point where the 145 deg. thermostat finally opens, all power will be removed and the heater will begin to cool and the green LED will be off until the stat re-closes.
Thus in normal operation the temperature is controlled in the range of the selected lower-temperature stat and 145 deg. The behavior of this control loop is going to depend a lot on the thermal response of the heater-roller mass. If the temp were to drop below the threshold of the low-temp switch, it will close and again supply the higher average voltage to the heater to bring it quickly up to temp, but otherwise it seems that the 145 deg. thermostat will do most of the controlling. It's a pretty clever design, based on a few inexpensive parts.
So the answer seems to be to substitute the new 160 deg. stat for the 145 degree one, which will allow the laminator to reach a higher temperature before it shuts off. However, one could also replace one of the low-temp stats and thus reverse the function, so that the full voltage would be applied until the 145 stat opens, which would presumably maintain the temperature between 145 and 160 deg.
Thoughts? I guess its time to take some temperature measurements.
73, Bob W9RAN